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TITLE Bridge Inspector's Training Manual.. INSTITUTION Federal Highway Administration (DOT), Washington, D.C. Bureau of Public Roads. PUB DATE 72 NOTE 241p.; Corrected Reprint 1971 AVAILABLE FROMSuperintendent of Documents, U.S. Government Printing Office, Washington, D.C..20402 (GPO 19720-930, $2.50)

:MRS PRICE MF-$0.65 HC-$9.87 DESCRIPTORS Building Trades; Civil Engineering; Component ' Building Systems; *Construction (Process); *Curriculum Guides; Equipment; *Inspection; *Job Training; *Manuals; Skilled Occupations; Vocational Education IDENTIFIERS *Bridge Inspectors

ABSTRACT A guide for the instruction of bridge inspectors is provided in this manual as well as instructions for conducting and reporting on a bridge inspection. The chapters outline the qualifications necessary to become a bridge inspector. The subject areas covered are: The Bridge Inspector, Bridge Structures, Bridge Inspection Reporting System, Inspection Procedures, Bridge Component Inspection Guidance, and Reports and Recommendations..The duties of an inspector and the requirements for his training are laid out in chapters one through four. Chapter five covers the construction and design aspects of bridges together with the explanation of mechanical principles. The nature and theory of bridge construction occupies approximately two thirds of the manual. The rest of the manual covers the inspection field book, inspection equipment, foundation movements and effects on bridges, the nature of underwater inspections, and structural bridge deficiencies._ There are extensive diagrams, photographs, a glossary of bridge engineering and inspection terms, and a 62-item bibliography. (KP) FILMED FROM BEST AVAILABLE CO

BRIDGE INSPECTOR'S TRAINING cc MANUAL 70

_ II I I I 1111VILLI,4

41. NOTICE TO PURCHASERS This is a new publication entitled Bridge Inspector's Training Manual. There wily be annual supplements published by the Federal Highway Ad- ministration and sold individually by the Superintendent of Documents. If you wish to be notified of the availability of these supplements, fill out the form below and return it to the Superintendent of Documents. This is not an order form. You will receive an order form upon notification of the availability of each supplement.

REQUEST FOR. NOTIFICATION

Notification Number N-388 To: Superintendent of Documents U.S. Government Printing Office Washington, D. C.. 20402 Please notify me of all supplements to Bridge Inspector's Training Manual when each becomes available.

Name Street address City and State ZIP Code BRIDGE INSPECTOR'S TRAINING MANUAL

U. S. DEPARTMENT OF TRANSPORTATION FEDERAL HIGHWAY ADMINISTRATION BUREAU OF PUBLIC ROADS WASHINGTON, D. C. 20591

Corrected Reprint 1971 For sale by the Superintendent of Documents, U.S. Government PrintingOffice Washington, D.C. 20402 - Price S2.50 ACKNOWLEDGEMENTS

The Bridge Division of the Office of Engineering and Cperations of the Bureau of Public Roads in cooperation with the Chairman of the Subcom- mittee on Bridge Maintenance of the Operating Committee on Mainte- nance and Equipment, American Association of State Highway Officials (A.A.S.H.O.), along with other affiliated State highway engineers, has prepared this Bridge Inspector's Training Manual. The help of all whose efforts and encouragement were of aid in completing this venture is acknowledged. Thanks are due to many individuals and state organizations for a large number of illustrations used in the text, a practical indication of the interest all concerned have exhibited in completing this project. To Mr. Vernon W. Smith, Assistant Highway Maintenance Engineer, Georgia State Highway Department; Mr. Samuel M. Cardone, Engineer of Structure Maintenance, Michigan Department of Highways; and Dr. Robert A. Norton, Engineer of Bridges and Structures, Connecticut De- partment of Transportation, Bureau of Highways, goes a special note of thanks. Mr. Smith contributed the material on the inspection reporting system contained in Chapter III. The text in Chapter VI covering reports and recommendations, is essentially the work of Mr. Cardore. Chapter II, Bridge Structures, represents the diligent efforts of Dr. Norton. Finally, acknowledgement is in order for the assistance provided by the Silver Spring, Maryland, Operation of Link Division of Singer Com- pany in the assemblage and shaping of the manual into its final form. TABLE OF CONTENTS

Page INTRODUCTION ix CHAPTER I. THE INSPECTOR 1-1 Section 1. Qualifications, Duties and Equipment 1-1 Section 2. Safety 1-2 CHAPTER II.BRIDGE STRUCTURES 2-1. Section 1. History, Materials, and Types 2-1 Section2. Elements 2-10 Section3. Mechanics 2-12 CHAPTER III.BRIDGE INSPECTION REPORTING SYSTEM 3-1 Section 1. Introduction 3-1 Section 2. Preparation for Inspection 3-2 Section 3. Preparing theInspector's Notebook 3-3 Section 4. Structure Evaluation 3-8 Section 5. Standard Forms 3-11 CHAPTER IV.INSPECTION PROCEDURES 4-1 Section 1. Sequence of Inspection 4-1 Section 2. Systematic Inspection Procedures 4-2 CHAPTER V.BRIDGE COMPONENT INSPECTION GUIDANCE 5-1 Section 1. Concrete 5-2 Section 2. Steel 5-8 Section3. Timber 5-11 Section4. Wrought Iron and Cast Iron 5-16 Section 5. Stone Masonry 5-17 Section 6. Aluminum 5-18 Section 7. Foundation Movements 5-18 Section 8. Abutments 5-25 Section 9. RetainingWails 5-29 Section 10. Piers and Bents 5-30 Section 11. Pile Bents 5-34 Section 12. Concrete Beams and Girders 6-37 Section 13. Steel Beams and Girders 5-41 Section 14. FloorSystems 5-44 Section 15. Trusses 5-48 Section 16. Diaphragms and Cross Frames 5-53 Section '17. Lateral Bracing, Portals, and Sway Frames 5-55 Section 18. Metal Bearings 5-60 Section 19. Elastomeric Bearings 5-66 Section 20. Decks 5-69 Section 21. ExpansionJoints 5-71 Section 22. Railings, Sidewalks, and Curbs 5-73 Section 23. Approaches 5-78 Section 24. Bridge Drainage 6-80 Section 25. Dolphins and Fenders 5-81 Section 26. Waterways 5-84 Section 27. Box Culverts 5-93 Section 28. Paint 5-95 Section 29. Signing 5-96 Section 30. Utilities 5-99 Section 31. Lighting 5-100 Section 32. Movable Bridges 5-107 Section 33. Underwater Investigations 5-117 Section 34. Suspension Spans 5-119

vii Page CHAPTEP, VI. REPORTS AND RECOMMENDATIONS 6-1 6-1 Section 1. Reports 6-2 Section2. Recommendations G-1 GLOSSARY B-1 BIBLIOGRAPHY I-1 INDEX

viii INTRODUCTION

The bridge structures of today reflect the technological advances in design, construction, and safeguards that have evolved over the years. Neverthe- less, these advances have not precluded unfortunate and, in some instances, tragic occurrences. The collapse of the Silver Bridge, in 1967, aroused increased interest in the inspection and maintenance of bridges and prompted the United States Congress to add a section to the Federal-Aid Highway Act of 1968 requiring the Secretary of Transportation to establish a national bridge inspection standard and to develop a program to train bridge inspectors. The purpose of this manual is to provide guidelines for the training of bridge inspectors. It is not intended to provide a definitive treatment of bridge inspection. It is neither an inspection manual nor a textbook for bridge inspections. This manual is, however, a guide both for instruction and for the conduct of bridge inspections. Chapter I of this manual outlines, in general terms, the primary duties of the bridge inspector, the essential requirements for the training of bridge inspectors, and the prerequisite qualifications for individuals selected for such training. Chapter H provides a simplified classification of bridge types and a rudimentary explanation of simple mechanics. The planning of a bridge inspection operation and the use of an inspection field book are explained in Chapter III. Chapter IV describes the methodology and the procedural sequence to be followed in conducting a bridge inspection. Chapter V covers the characteristics and weaknesses of the major construction materials, and explains the nature and causes of foundation movements and their effects upon bridges. A description of typical structural deficiencies composes the bulk of this chapter. A brief discussion of the methods of reporting inspection results and making recommendations is contained in Chapter VI. The manual also contains a glossary of commonly used bridge engineering and inspection terms and a short bibliography. The success of any training program is highly dependent on the qualifications and motivation of the individuals concerned. While some states currently use graduate engineers to conduct bridge inspections, this will not always be possible. A tbfght, industrious, high school graduate or, perhaps, a graduate of a junior o two-year college who is motivated, interested, and willing to work can com ensate for the lack of formal education. A realiza- tion of the importance or this work and the dedication and determination to do a good job are essential prerequisites. Good health and physical agility are two highly desirable qualifications. While not necessary, some experience in structural erection or construction is also desirable. Aside from physical fitness, the inspector trainee must be literate, havean understanding of drafting, be capable of reading bridge construction plans, and be able to use simple inspection equipment.

ix The critical ingredients of the bridge inspector's tasks are the care he exercises in the inspection of a bridge, the thoroughness with which he covers every aspect of the structure, the clarity arid comprehensiveness with which he reports the conditions he finds, the soundness of his recommendations, and the enthusiasm with which he approaches each day's work. The task of inspecting a bridge is, in most instances, a com,)lex technical assignment requiring specialized skills and experience. Moreover, each bridge inspector shares a tremendous dual public responsibility. He is relied upon to guarantee public safety and to protect public investment with respect to bridges. The inspector discharges this responsibility through inspection and the reporting of those bridge conditions and situations which presently impair, or may potentially impair, either public safety or investment. Each bridge inspector must, therefore, be properly and thoroughly trained to recognize, record, evaluate, and report bridge conditions. CHAPTER I

THE INSPECTOR

Section1. QUALIFICATIONS, DUTIES, inspector will be occasionally required to work AND EQUIPMENT during periods of adverse weather. d. Skills. The bridge inspector should be able 1-1.1 General. to letter legibly and read at the level of the It is the responsibility of the bridge engineer of average high school graduate. He should pos- today to utilize his technical skill to preserve sess average mechanical aptitude and a working and maintain all existing bridges so that they knowledge of the use of measuring devices such may continue to serve us until they can no as rulers, tapes, feeler gauges, protractors, cali- longer endure the burdens of modern day load- pers and thermometers. He should have the ings. All bridges, regardless of type, have cer- ability to read bridge plans, visualize details, tain basic common components. This publica- operate a camera, and draw technical sketches tion will familiarize the potential inspector with of bridge components. He should have an the various types of bridges and their compo- awareness of potential hazards and exhibit a nent parts. It will assist in the training of se- serious attitude toward the safety precautions lected individuals in the inspection, identifica- to be taken while climbing and inspecting tion, and reporting of deterioration, malfunc- bridges. tioning, and potential hazards of the nation's e. Attitude. The inspector must approach bridges. In this chapter the qualifications and each task critically with the expectation of de- duties of the inspector, and the tools and equip- tecting serious defects or deficiencies. ment he needs will be outlined. f. Motivation. The inspector must want to do a good job. All of the above qualities are of 1-1.2 Qualifications of the Inspector. little value without the determination to per- a. Training and Education. Graduation from form well. a standard or vocational high school is a minimum requirement. Completion of two years of 1-1.3 Typical Duties of the Inspector. engineering school or the completion of a two- year technical course in an institute of applied a. Assists in the planning and preparation of science, is desirable. bridge inspections b. Experience. While not Mandatory, five b. Inspects bridge components for deteriora- years of experience in one or more of the fol- tion lowing related fields is desirable: c. Sketches bridge components (1) Structural maintenance d. Photographs various problem areas (2) Structural inspection e. Takes technical measurements (3) High steel construction f. Records rotation and translation data for (4) Surveying appropriate components c. Physical Ability. Inspecting, sketching, and g. Notifies supervisor of hazardous condi- photographing bridge components while in dif- tions ficult positions or at great heights willsome-, times be necessary. The applicant should be able h. Makes basic computations to climb structural steel without difficulty. The i.Maintains records of inspection results

1-1 1-1.4 Tools and Equipment. (2)Chipping hammer (6 ounce) a. Special Equipment. The inspecting agency (3) Scraper(2inch) has the responsibility for providing access to (4) Inspection mirror on a swivel head the various locations on the structure that and extension arm cannot be observed and/or inspected without (5)Center punch the use of special equipment. The following is a (6) Scribe list of some of the special equipment that may be required : (7) Calipers (1) Ladders (8) "C"-clamps (9) Plumb bob (2)Scaffolds (Travelers or cabling) (3) "Snooper" or "Cherry Picker" (10) Straight edge (Truck-mounted bucket on a hydraulically oper- (11)I 00 foot tape ated boom (or on a platform truck)) (12) Feeler gauges (4)Burning, drilling, and grinding equip- (13)Sounding line ment (14) ThermometersAir and Contact (5) Sand or shot blasting equipment (15) Penetrating Oil. (6) Boat or barge (16) Binoculars (7) Diving equipment (ScuLa or hard hat) (17) Camera (Color or black and white (8) Sounding equipri.o.nt (Lead lines or film) electronic depth finder:; (18) Safety belts (9) Transitlevel,orother surveying (19) Paint film gauges equipment (20)Fieldbooks,inspectionforms, clip (10Television camera for underwater boards, chalk, keel or markers use dosed circuit television with video tape (21) Screw driver (Large) recorder (22)Heavy duty pliers (11) Magnetic locator for rebars (23)Protractor (12) Helicopters (24)Flashlight (13) Air jet equipment (25)Pocket knife (14)Air breathing apparatus (26)Increment borer (15) Mechanicalventilationequipment (27) Corrosion meter (Blowers and air pipes) (28) Wire brush (16) Pre-entry air test equipment (De- vices to test oxygen content and to detect nox- (29)Ice pick iou:t gasses) e. Clothing.The inspector should dress in ap- (17) Ultrasonic equipment propriate seasonal work clothes. Overdressing (18) Radiographic equipment in bulky, cumbersome clothing is notrecom- mended as it hinders freedom of motion and (19) Magnetic particle equipment will often prevent entrance into confined areas. (20)Dye penetrants Three important articles of wearing apparel are NOTE : Ultrasonic, radiographic, magnetic par- boots, leather gloves and the safety hat. Boots ticle; and dye penetrant and other non-destruc- should be of the bridge shoe type with either tive methods are beyond the scope of the aver. cork or rubber soles. Overshoes, such as rubber age inspection. In this manual they are referred arctics, must be completely buckled if worn, es- to as the "more sophisticated methods" of test- pecially while walking on the structure. i ng. Section 2.SAFETY b. Standard Tools. The inspector should be provided with and able to use the following 1-2.1 General. tools : The safety of the bridge inspector is of the ut- (1) Pocket tapes' and folding rules most importance. While the work may be haz-

1-2 ardous, the accident probability may be limited c. Reflective vests or belts when working in by proceeding cautiously. The following rules traffic. should be observed: d. Life preservers or work vests when work- a. Always be careful, use good judgment and ing over water. prudence in conducting your activities, both for e. Shoes with cork, rubber, or some other your own safety and that of others. non-slip soles. b.If you wear glasses, wear them when climbing. The wearing of bifocals is an excep- 1-2.4 Special Safety Equipment. tion to this rule. Only regular single lens glasses a. A life line or belt must be worn when should be worn while climbing. Where work re- working: quiring close-lip viewing is to be performed, a (1) At heights over 20 feet. separate pair of glasses with lenses ground for (2) Above water. this purpose should be worn. (3) Above traffic. c. Do not drink alcoholic beverages before or b. A life-saving or safety skiff should be pro- during working hours. They impair judgment, vided when working over large rivers or har- reflexes, and coordination. bors; the skiff should have life preservers and life lines on board. 1-2.2 Bridge Site Organization. c. Warning signals, barricades, or flagmen a.General. The safety of personnel and are necessary when the deck is to be inspected, equipment and the efficiency of bridge inspec- or when scaffolding or platform trucks are used tion operations depend upon proper site organi- for access to the undersides or bridge seat of a zation. structure. Refer to the Manual on Uniform b. Personnel. All individuals who are as- Traffic Control Devices (MUTCD) for specific signed to work aloft must be thoroughly trained traffic control procedures. in the rigging and use of their equipment, i.e., scaffolds, working platforms, ladders and safety 1-2.5 Climbing of High Steel. belts. The plans for inspection should give first a. It is preferable to work from a traveler, consideration to safeguarding personnel from catwalk or platform truck, if possible. possible injuries. NOTE : On old ladders and catwalks, proceed c. Equipment. Inspection equipment, highway with extreme caution. traffic barricades, and signs should be arranged b. Scaffolding. When using scaffolding, the according to the plLn of inspection so as to following precautions should be observed : accomplish aslittlehandling,unnecessary (1) Scaffolding and working platforms movement, and repositioning as possible. Vehi- should be of ample strength and should be cles not directly involved in the inspection proc- secure against slipping or overturning. ess should be parked so as to prevent congestion and avoid interference in the area of inspection. (2) Hanging scaffolds and other light scaffolds supported by ropes should be tested before d. Orderliness. Individuals should develop or- using by hanging them a foot or so from the derly habits in working and housekeeping on ground and loading them with a weight at least the job. four times as great as their working load. (3) Scaffolds should be inspected at least 1-2.3 Personal Protection. once each working day. It is important to dress properly. Keep clothing c. Ladders should be used as working plat- and shoes free of grease. Always wear the fol- forms only when it is absolutely necessary to do lowing required protective equipment : so. When using ladders the following precau- a. Hard hat with a chin strap. tions should be observed : b. Goggles, face masks, shields, or helmets, (1) Make certain that the ladder to be used when around shot blasting, cutting, welding, is soundly constructed. If made of wood, the etc. material should be straight-grained and clear.

1-3 Courtesy of Bethlehem "feel Co. Figure 1-1.Platform being used on high steel.

L2) Ladders should be tested to make sure f. Catwalks, scaffolds, and platforms should they can carry the intended loads. have hand rails and toe boards to keep tools or (3) Ladders should be blocked at the foot other objects from being kicked off and becom- or tied at the top to prevent slipping. ing a hazard to anyone below. (4) Personnel should be cautioned fre- g. Always watch where you are stepping. Do quently about the danger of trying to reach too not run or jump. far from a single setting of a ladder. h. Do not climb if you are tired or upset. d. Planks or platforms may be used where necessary (fig. 1-1). 1-2.6 Confined Spaces. (1) Planks should be large enough for the a. General. In recent years there has been an span. increasing use of hollow structural members of (2) Never use a single plank. Two planks the tubular or box-section types large enough to are a bare minimum; they should be attached permit a man to enter the interior of the mem- by cleats 18" apart. ber. In-bridge work, boxes Are used both in e. Keep all catwalks, scaffolds, platforms, etc., large truss bridges and in box girder bridges free from ice, grease, or other slippery sub- with rectangular or trapezoidal box-sections. In stances or materials. these types of members, the interior is often 1-4 closed off at both ends, forming a closed box. (b) Where the presence of other gases is This protected interior is high in corrosion re- suspected, test for such gases should be con. 2istance even in the bare metal state, a great ducted using approved gas-detecting devices. advantage in the maintenance of the structure. The following gases should be considered: In some closed sections *a closable, watertight, Carbon Dioxide and vaportight access manhole is provided to Carbon Monoxide permit inspection of the interior. While the Hydrogen Sulfide box-section offers both structural and mainte- Methane nance advantages over other types of sections, Any combustible gas there are certain health hazards of which the (c) If the oxygen content of the air in maintenance inspectors, and others who may be the space is below 19%, or if noxious gases pres- involved with these types of sections, should be ent are equal, or in excess of 125% of the aware. Threshold Limit Values, established by the b. Hazards. No health hazard exists in con- American Conference of GovernmentalIn- fined space if there is proper ventilation. How- dustrial Hygienists, no person should be al- ever, a hazardous atmosphere can develop be- lowed to enter such space unless mechanical cause of a lack of sufficient oxygen or because of ventilation is applied to the space until the oxy- a concentration of toxic gases. Oxygen defi- gen content and gas content meet the above lim- ciency can be caused by the slow oxidation of its for a minimum period of fifteen (15) min- organic matter which has become moistened. utes. Toxic gases may seep into the confined space or (2)Ventilation During Occupancy. may be generated by such work processes as (a) All confined spaces should be me- painting, burning or welding. The confined chanically ventilated continuously during occu- space may be of such small volume that air con- pancy irrespective of the presence of gas, the taminants are produced more quickly than the depletion of oxygen, or the conduct of contami- limited ventilation of the space can overcome. nant-producing work. Persons should not be allowed to work in con- (b) Where contaminant-producing oper- fined spaces containing less than 19% oxygen ations are to be conducted, the ventilation unless provided with air-breathing apparatus. scheme should be approved by an Industrial Hy- However, as noted above, *a space with sufficient giene Engineer, Safety Engineer, Marine Chem- oxygen content can become unfit for human ist, or others qualified to approve such opera- occupancy if the work conducted therein pro- tions. duces toxic fumes or gases. Such space should (3) Air Tests During Occupancy. be occupied by the inspector only after adequate (a) If toxic gas presence or oxygen de- ventilation. pletion is detected or suspected, air tests similar c. Safety Procedures. to the Pre-entry air tests should be conducted during occupancy at fifteen (15) minute inter- (1)Pre-entry air tests. vals. (a) Tests for oxygen content should be (b) Where contaminant-producing op- conducted with an approved oxygen-detecting erations are conducted, air tests should be con- device. A minimum of two tests should be conduct-id to determine the adequacy of the ventila- ducted. tion scheme.

1-5 CHAPTER II

BRIDGE STRUCTURES

2-0.0 introduction. Co les in the battle against the Etruscans in the This chapter discusses briefly the development lath 6th century B.C. It reportedly was a of various types of common bridge structures, wooden bridge resting on piles. Another notable their components, the materials of which they ancient bridge was constructedby Julius are constructed, and the manner by which loads Caesar across the Rhine River in Germany in are transmitted through the several parts of a 55 B.C. (fig. 2-2). This, too, has been described bridge structure to its foundations. The bridge as being a wooden bridge resting on piles. maintenance inspector is concerned with all bridges whose structural integrity is essential 2-1.2 Clapper Bridge. to the safety of the traveling public and to the Another very old type of structure, of which uninterrupted use of the highway. Minor cul- there are still a few remaining 3xamples, is the verts are normally the responsibility of the hy- stone slab or "clapper" bridge, shown in figure draulic or drainage engineer rather than of 2-3. Although stone is not strong in taision, bridge maintenance; personnel. Similarly, spe- quality granite, or other hard stone, may be cialized and compi.,,x structures such as movable bridges or suspension bridges, whose inspection requires specialized personnel and, perhaps, the services of consulting engineers, are also beyond the scope of the average bridge maintenance inspector. The Bibliography will provide the bridge maintenance inspector with additional information about the history, types of bridges, and bridge construction materials. A Figure 2-1.Simple log bridge. few of the more important or classic works on the subject of bridges and structures are also listed. Some of the older works may be out of print and may be available only through large technical reference libraries, or the personal libraries of "old-time" engineers.

Section 1. HISTCRY, MATERIALS, AND TYPES

2-1.1 Log Bridge. The earliest bridges were, undoubtedly, logs or tree trunks set across a stream or chasm (fig. 2-1). Since timber cannot endure for thousands or even hundreds of years, there are no known remaining examples of this early type of bridge construction. One of the earliest bridges on record was that constructed over the Tiber River at Rome, and defended by Horatius Figure 2-2.Caesar's bridge.

2-1 the Etruscans. The Romans used stone arches for the construction of both aqueducts and highways (fig. 2-6 and 2-7). Many examples of their work remain today not only in Rome but throughout the once vast Roman empire extend- Figure 2-3.Stone clapper bridge. ing up into Spain and France. With the decline of Roman civilization there followed a period used for simple spans several feet in length. during which the art of bridge building lapsed There is an ancient "clapper" bridge of three to such an extent that no new bridges of any spans still standing at Dartmoor, England. importance were constructed for several centu- ries. It was not until the Middle Ages, when the 2-1.3 Stone Masonry Arch Bridge. Crusades began, that bridge building was re- a, False Arch. The use of stone masonry for sumed to any significant extent. Stone masonry the construction of arches dates back to at least arch construction continued to be the principal 3,000 years before the Christian Era. The type of bridge structure from the 12th century Egyptians and other people of the eastern Med- until the 18th century. Although the Romans iterranean region first developed the corbelled had specialized in the construction of semi-cir- or false arch (fig. 2-4) . This type of arch is cular arches, the bridges of this period varied formed by projecting stones from each side of from the pointed or Gothic arch t .2-8) to the an opening until they meet at the center. Since flat or elliptical arch (fig. 2-9). the projecting stones carry the applied loads as cantilever arms, rather than by direct compres- 2-1.4 Cast Iron and Timber. sion of the individual stones, as is the case with During the late 18th century and the first half a true arch ring, they are called false arches. of the 19th century, new materials and new Examples of this type of construction are found types of bridges began to appear. The first of in the pyramids of Eygpt dating back to 3000 to these new materials was cast iron, which was 4000 B.C., and at Mycene in Greece, dating back to 1300 B.C. These structures serve as en- trances to underground vaults and to fortified palace walls. It is not known whether these earlier arches were used for bridges which could carry traffic. b. True Arch. It is generally agreed that the Etruscans, who lived in north centralItaly from the 8th to the 4th century B.C., were familiar with the true stone arch (fig. 2-5) and that the Romans, who developed this form of construction to its peak during the period from Figure 2-5.True arch. 300 B.C. to 200 A.D., learned their skills from

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Figure 2-4.Cor.':elled or false arch. FigUrc 2-6. Roman aqueduct. 2-2 most bridges were constructed by empirical methods, frequently with the use of models tested to destruction. The first long-span truss of the Whipple type was constructed across the Ohio River at Steubenville, Ohio, in 1864. The end posts and all other compression members were of cast iron while all tension members were of wrought iron. A few of these old cast and wrought iron trusses remain in service Figure 2-7.Roman bridge. today.

2-1.6 Modern Era. a. Steel. The modern era of bridge building can be said to have begun with the development, in 1855, of the Bessemer process of making steel, followed a few years later by the open- hearth, or Siemens-Martin, process. The first important bridge in America to use the new =lb material was the Eads Bridge over the Missis- 1.1 11.1 sippi River at St. Louis. This structure, a three-span steel arch bridge more than 1,500 feet in length, was completed in 1874requir- Figure 2-8.Gothic arch. ing 6 years for its construction. b. TrUSS Bridge. Although the Eads Bridge was of steel arch construction, many of the 011110110."-- -"1121111111111 bridgesbuilt during the next fifty or more years "NlNEIONNW IV UMNNMIE/ IN/ In/ were steel trusses. So many different types of 11/ 1/ trusses were developed that it is not possible to describe them all here. However, the sketches in figure -2 -10 show many of the more common types used throughout the country. Although Figure 2-9.Elliptical arch. for crossings of moderate span, the truss types are rapidly being replaced by beam or girder first used in the construction of an arch bridge construction, the many truss bridges still in across the Severn River in England in 1776. service are an important class of structures. The first suspension bridge in America was Most of the older trusses require especially builtin1796 at Uniontown, Pennsylvania, close and knowledgeable inspection since they using wrought iron chains. Although the use of were constructed before the advent of the heav- timber cannot be considered new in bridge ier live loads such as oil trucks, tandem trailers, building, the development of the timber truss and concrete mixers that travel our highways by Ithiel Town, and the introduction of the com- today. Trusses are often located on secondary bined timber and wrought iron truss by Theo- roads where their proper maintenance may dore Burr and William Howe in the early have been overlooked. The failure of one weak- 1800's, led to the development of our modern ened member or connection of a truss bridge railway and highway systems. can result in the complete collapse of the structure. 2-1.5 Trusses. e. Girder Bridge. Concurrently with the de- The first rational analysis of the stresses in the velopment of truss bridges came the develop- members of truss spans came in a book pub- ment of beam, or girder, bridges (fig. 2-11). lished by Squire Whipple in 1847 entitled, "A What is probably the first box girder construc- Work On Bridge Building". Until that time tion was used for the Brittania Bridge over the 2-3 THROUGH HOWE TRUSS THROUGH PRATT TRUSS

THROUGH WARREN TRUSS QUADRANGULAR THROUGH WARREN TRUSS

THROUGH WHIPPLE TRUSS CAMEL BACK TRUSS

THROUGH BALTIMORE TRUSS K - TRUSS

at 2C

PONY TRUSS 3E THROUGH TRUSS DECK TRUSS Figure 2-10.Truss bridges.

2-4 THROUGH GIRDER DECK GIRDER I BEAM Figure 2-11.Girder bridges. Menai Strait in Wales, built in 1850. The gir- strength of concrete with the great tensile ders consisted of two wrought iron rectangular strength of the reinforcing steel. The reinforc- tubeseach carryingatrack forrailroad ing functionally replaces the portion of the con- trains. As steel rapidly replaced wrought iron crete that is in tension. The first reinforced con- for girder construction, the most common type crete slabs were made in France by Francois of short span bridge used the riveted built-up Hennebrique in 1880. The first reinforced con- plate girder, generally consisting of a web cretearch U., geinAmerica,using the plate,sideplates, flange angles, and flange "Melan" system of I-beam reinforcement, was plates(fig. 2-12). As steel plants developed constructed in Cincinnati, Ohio, in 1894. Dur- larger rolling mills, it was possible to substitute ing the first half of the 20th century, there were rolled beams of I-sections for riveted girders. In rapid advances in the use of reinforced concrete the past 25 or more years, the use of welding first as simple span slab or beam bridges, has replaced riveted construction for spans too then as rigid frames, and, finally, as prestressed long for the rolled beam sections. Many of our concrete bridges, which first appeared after modern highway bridges are either rolled beam World War II (fig. 2-17). Prestressed concrete or built-up girder structures (fig. 2-13). utilizes very high strength steel wire to apply stead of being constructed with one or more an eccentric compressive force to the ends of simple spans (fig. 2-14), they may consist of the concrete beams to produce both axial com- continuous beams of two or more spans (fig. pression and a bending moment of opposite sign 2-15), or they may consist of spans with canti- to that of the design loads. This permits the lever overhangs support' - a simple suspended structureto withstand much greater loads. span (fig. 2-16). Even when the superstructure of a bridge con- d. Reinforced Concrete. Reinforced concrete sists of steel trtoses, beams, or girders, rein- construction combines the high compressive forced concrete plays an important role in the totalstructure. The abutments, wing walls, Cover plate piers and deck are almost always made of reinforced concrete. e. Twentieth Century Trends. The steel truss continued tobe the favorite for long span bridges well into the twentieth century, although concrete and masonry arches were also Flange angle used extensively. For smallerspans, reinforced concrete slabs, "Tee" beams, wide flange steel, and built-up steel plate girders were all used. The development of parkways in the late 20's and early 30's generated another structure, the Side plate slender and attractive reinforced concrete rigid frame bridge. Stone-faced frames and small arches made highway bridges more attractive aesthetically. New York's Westchester Park- Figure 2-12.Riveted pla:;e girder ways and Connecticut's Merritt Parkway fur- 2-5 Buffo, of Daoe Venn., door PC haha,at heft P." 6,oli pool Approoth .1:6 2 RooOna,. ..toy deg] Bute Pooch/cry dock WON ban1 A.Ibmspw, 0.6.1.1rAn -POrow, .mn.ckw OW 0. CCt -Po " r CON bO. Dlme (canpa.) 2 Ee bash En " Jeoe ovfn nee ANimminnomannumanamm,S44Kee 10ufline of coon 004 Ch.fer 416711" v BCIe Outline of p Oopneogrn Diaphregm N'"" Beo!mq elf knee .hiNeWil" 6;3frzSok plot. Coo, plot. Ancnobolls Fixed bearing Bose plats ConsInxbonMIA Uy.oy Fidehed wound --- Finqhed would Brews, concrete Ode Tin.. ph. girdConeemoon karroy OVER PIER Courtesy of Clarkson and Clough Associates. OVER ABUTMENT Figure 2-13. Typical highway structure, exploded view. frames, damaged members, bearings, eyebars, leave blank every third or fourth page for this and heavily corroded areas. purpose. (2) Suspension Bridges. Sketches of sus- e.Alignment. A section of thenotebook pension bridges should include, but not neces- should be reserved for recording the horizontal sarily be limited to, anchorages, towers, cable and vertical alignment of the structure. Align- bents, tower saddles, cable bands, suspender ment should be checked for structures are saddles, suspender connections, and stiffening long, or show evidence of misalignment. truss connections. The critical areas on the (1) Substructure Drawings. Drawings of stiffening trusses are the same as those listed each substructure unit should include a side ele- under "Trusses" in the previous paragraph. It vation view and the two end elevation views. is particularly important to detail rocker bear- These sketches should be large enough so that ings for towers and cable bents when they exist, the structure's horizontal and vertical align- the main cable cross section, heavily corroded ment can be noted on the sketches after they members, cable bands, and cable wrappings. have been determined. (3) Swing Spans. Critical areas include (2) Superstructure. Sketches showing the truss details and connections, machinery, locks, plan and elevation views of the superstructure electrical systems, controls, and girder details are necessary. The horizontal alignment.should for girder type swing spans. be noted on the plan view of the structure, and (4) Bascule Spans. The required details in- the vertical alignment of the elevation view. chide counterweights, trunnion details, locks, f. Environmental Features. The environmen- machinery, buffers, cables, controls, corroded tal features that should be included are terrain members, and details of connections of trusses features, stream profiles, high water elevation, and girders. spur dikes or other protection devices, slope (5) Vertical Lift Spans. Critical areas in- protection, channel protection, and the channel clude cables, anchorages for the cables, trun- location where it passes under the structure. In nions, sheaves, guides, limit switches, counter- some instances it is desirable to show the chan- weights, counterweight balance chains, buffers, nel condition upstream and downstream from locks, machinery, electrical system, controls, the structure, The horizontal and vertical align- corroded members, and bearings. ment of the approach roadway should also be (6) CantileverBridges. Oncantilever shown. bridges, sketches are generally required for the g. Underwater Investigation. Plots of the hinges for the suspended span, rockers, bear- contour of the stream bottom should extend to a ings, the hold-down devices,if any, in the radius of ,;.t least 100 feet from each pier. The anchor spans, truss or girder details, and the purpose of the contour plots is to determine corroded areas. the extent of the scour. On the contour draw- (7) Bearing Devices. Since bearing devir 3 ings, a plan view of the foundation should be are a frequent source of trouble they should be included. inspected with particular care. Sketches should be made of each major bearing device showing h. Specialist Reports. The final section of, the its position, as in figure 3-6. Sketches should be notebook should include the reports of mechani- made of any bearing that is not functioning cal, electrical, or other specialists. properly. (8)Miscellaneous Sketches. Sketches of Section 4. STRUCTURE EVALUATION fenders, dolphins, and aerial and navigational lighting will sometime-.; be required. Special ter- 3-4.1 General. rain features or unusual slope protection or A bridge is typically divided into- two main channelprotectionconditionswillrequire unitsthe substructure, and the superstruc- sketches. Sketches may also be required for ex- ture. For convenience the deck, is sometimes pansion devices. considered as a separate unit. These basic units (9) Additional Sketches. Since additional may be divided into structural members, which, sketches may be required, it is a good practice to in turn, nov be further subdivided into ele- 3-8 CONTINUOUS GIRDER

00 00 00 00 00 00 00 00 00 00 00 00 00 00 DO ga,L, ...... o. ...M. 4.1. Ix.

SPANDREL- FILLED ARCH OPEN SPANDREL ARCH

RIGID FRAME CONCRETE

JC E__1

SLAB SECTION T-BEAM SECTION

CONCRETE SLAB ( PLAIN ) CONCRETE T- BEAM Tigure 2-17.Concrete bridges.

2-8 Figure 2-18.Bascule bridge. lagAilk billIV

Figure 2-19.Swing bridge.

1,710 feet, was that of the great cantilever pletion of the Brooklyn Bridge. The success of bridge across the Firth of Forth.) Probably the the Brooklyn Bridge led to the building of other most famous suspension bridge is the Brooklyn long suspension spans, but the upper limit of Bridge. built over the East River in New York span length seemed to have been reached until City in 1883 by Washington Roebling. It had the Philadelphia-Camden Bridge over the Dela- the longest suspension span in the world (1,595 ware River was opened in 1926 with a 1,750 - feet), until the Williamsburg Bridge, also cross- foot span. In 1932, the George Washington ing the EaF" with a span of 1,600 feet, Bridge was opened, its 3,500-foot span almost was built almost 25 years later. Suspension doubling the previous record. It was followed bridge failures were common prior to the corn- by the Golden Gate, Mackinac Straits, and'the Verrazano Narrows bridges. The latter has the longest span between towers in the world, 4,260 feet. The destruction by aerodynamic forces of the original Tacoma Narrows bridge in 1940 led to considerable research into the effects of such forces, and to the strengthening of several major bridges. Although spans have more than doubled since 1883, the Brooklyn Bridge still stands as one of the great engineering achieve- ments of our times. A typical modern day sus- Figure 2-20.Vertical lift bridge. pension bridge is depicted in figure 2-21. 2-9 Figure 2-21.Suspension bridge.

Section 2. ELEMENTS unit into a rigid frame. The pier cap is most noticeable on rigid frame piers and tee-piers. 2-2.1 Substructure. Starlings or pointed nosings are used on river a. General. The substructure includes those piers to reduce the force of the water or ice parts of the structure which transfer the loads against the piers. from the bridge span down to the supporting ground. For a single-span structure the sub- 2-2.2. Superstructure. structure consists of two abutments, while for a. General. The superstructure includes all multi-span structures there are also one or those parts of the structure supported by the more piers (fig. 2-13). Sometimes steel bents or substructure. It transfers the loads which must towers are used instead of piers. The loads are be carried to the bearings on the abuilincnts or applied to the substructure through the bearing piers. plates and transmitted through the abutment b. Types. The reinforced concrete slab bridge walls or pier columns, to the footings. If the soil (fig. 2-17) has the simplest type of superstruc- is of adequate strength, the footings will dis- ture since the slab carries the load of the vehicle tribute the loads over a sufficiently large area. directly to the abutments or piers. On beam or If not, the footings themselves must be sup- girder bridges (figs. 2-11 and 2-17) the slab is ported on pile foundations extended down to a supported en steel, concrete, or timber longitu- firm underlying stratum. dinal members which, in turn, carry the loads to b. Abutments. The abutment is usually com- the abutments or piers(fig. 2-13). Finally, posed of a footing, a stem or breast wall, a there is the superstructure consisting of the bridge seat, a backwall, and wing walls. The deck, a floor system, and two or more main sup- backwall prevents the approach embankment porting members. soil from spilling onto the bridge seat, where c. Superstructure Elements.._ bearings for the superstructure are situated. The wing walls are retaining walls which keep (1) Deck. The bridge deck, either a con- the embankment soil around the abutment from crete slab, timber planking, steel grid, or steel spilling into the waterway or roadway which is plate, supports the live load directly and distrib- being spanned. When U-shaped wing walls are utes it to the floor system. used, parapets and railings are often placed on (2) Floor System. The floor system may top of them. consist of either closely spaced transverse floor beams or several longitudinal stringers carried c. Piers. Footings, columns or stems, and caps by transverse floor beams. In floors of this type, are the main elements of piers. The footings are the stringers are usually wide flange beams, slabs which transmit the load to the soil, rock while the floor beams may be plate girders, wide or to some other foundation unit such as piles, flange beams, or trusses. Where floor beams caissons, or drilled shafts. The columns or only are used, they may be either rolled beams stems transmit vertical load and moment to the footings. The cap receives and distributes the or plate girders. superstructure loads. River bridges, railway (3) Main Supporting Members. The main bridges, and some highway underpasses are supporting members transmit all loads from the likely to use the solid w...11 pier. Highway grade floor system to the supports at the piers and separations of normal width often use multi- abutments. The strength and safety of the legged piers, often with a cap binding the whole bridge structure depends primarily on the main

2-10 supporting members. These members may be stabilize the beams or trusses and distribute timber, steel, or concrete beams ; steel plate gir- loads between them. A diaphragm is usually a ders, timber or steel trusses ;steel or concrete solid web member, either of a rolled shape or rigid frames; arches of almost any mteria.1; or built up, while a cross frame is a truss panel or steel cables. Beams and girders are considered frame. Since portals and sway braces help to be single elements while trusses have several maintain the cross section of the bridge, they identifiable parts. The chords, which are gener- are as deep as clearance requirements permit. ally longitudinal members at the top and bottom Portals usually are in the plane of the end posts of the truss, carry the tensile and compressive and carry lateral forces from the top chord forces that make up the resisting moment of the bracing to the supports, Lateral bracing placed truss, just as,flanges dfor a beam. The verti- at the upper or lower chords (or flanges), or at cals and diagnonals of a truss, often called the both levels, transmits lateral forces (such as web members, carry the shear forces. Sloping wind) to the supports. Although X-bracing has chords also carry some of the shear forces. See alwaysbeenvery popular,theincreasing Section 2-3 for a further discussion of tension, widths of structures, as well as aesthetic consid- compression, moment, and shear. erations have led, to an increasing use of K-brac- (4) Bracing. The individual members of ing (fig. 2-22). Figures 2-10 and 2-13 illus- beam and girder structures are tied together trate the location of these members in the with diaphragms and crossframes, while bridge. trusses are tied together with portals, cross (5) Miscellaneous, Other components of frames, and sway bracing. Long structures, the superstructure are the curbs, scuppers, side- whether of the girder or truss type, also employ walks, parapets, railings, bearings, and expan- lateral bracing. Diaphragms and cross frames sion devices. Short span structures usually have

Truss orGircler

K FRAME X-FRAME Figure 2 -22.Bracing.

2-11 simple sliding plates on one of the bearings to accommodate changes in the length of the struc- I- 1 ture due to temperature changes whereas longer structures require rollers or rockers for this purpose. A short span structure usually has an open slot, a slot covered with a sliding plate, or Figure 2-23.Dead-load on simple span. a slot filled with elastomeric joint material to provide for expansion and contraction of the deck. However, long spans require elaborate finger joints to accommodate the greater amount of movement involved.

Section 3. MECHANICS Figure 2-24.Live load on simple span. 2-3.1General. Mechanics is that branch of physical science that force is that of gravity acting on the weight of the deals with energy and f,zces and their relation to structure itself(fig. 2-23), and on the vehicles the equilibrium, deformation, or motion of solid, (fig. 2-24), or on other live loads being carried by liquid, or gaseous bodies. Except for the action the structure. Other forces to be considered are of movable bridges while being operated, the those created by earth pressures(fig.2-25), vibrations of large structures, and the like, the buoyancy or uplift on that portion of a structure bridge inspector will primarily be concerned with which is submerged below water level (fig. 2-26); statics, or that branch of mechanics which deals wind loads on the structure, vehic:?s, or live with solid bodies at rest or forces in equilibrium. loads(fig.2-27);longitudinal forces due to changes in speed of the live load or due to friction 2-3.2Bridge Forces. at the expansion bearings (fig. 2-28); temperature The solid bodies to be considered are the substruc- change (fig. 2-29),'earthquake (fig. 2-30), stream ture and superstructure of the bridges to be inflow and ice pressure (fig. 2-31); and , in the case spected, while the forces exerted on them include of masonry structures, shrinkage and elastic rib various combinations of loads. The principal shortening. / / / / // / / / / / / / //

4--- .110. ...two,PM

BoxCulvert

Retaining Wall

Figure 2-25.Earth pressures.

2-12 2-3.3Stress. axial, transverse, rotational and torsional. Figures The load per unit ofarea is called unit stress. 2-32 and 2-33 illustrate the action of these Unit stress is a very widely used standard for forces. Both axial and transverse forces are measurement of safe load. Generally,a limiting gravity forces and are expressed in pounds, unit stress is established fora given material. kips (1000 lbs.), tons, or kilograms. When the This allowable unit stress multiplied by thecross axial or longitudinal loads exert a pullon the sectional area gives the safe load for the member. member, the force is said to be tensile; when the Since this manual can give onlya very elementary axial load pushes or squeezesa member, the introduction to the mechanics of structures, it force is compressive. In the pure case, axial will be limited to a consideration of the forces forces load the cross-sectional area uniformly due to dead and live loads actingon simple as shown in figure' 2-33. The formula for axial tension or compression members of simplespan stress is: structures. For an understanding of other forces and other types of structures, it is suggested that f=A the bridge inspector refer to standardtexts such where: f =stress as those listed in the Bibliography. Loadsor P =load forces acting upon membersmay be classified as A =cross-sectional area a. Tension. A simple tension member could be one of the sub-vertical members ofa through Baltimore or Petit truss (fig. 2-34). Both dead Water Surface and live loads cause downward vertical forces which pass from the roadway slab through the stringers and floor beams, each adding itsown dead weight force to that already being exerted / / / / / // // /i / on it. These combined forces are applied to the sub-vertical member in question through the t tttt tt floor beam connection to the truss. The tensile force acts on the entire cross-section (less rivet Figure 2-26.Bouyancy on pier. or other holes) of the member and produces a certain intensity of stress. If that intensity,or

w Figure 2-27.Lateral soh d load on truss and vehicle. / / / 77- 4--

/ Figure 2-30.Earthquake force /77 (may be in any direction).

Figure 2-28.Longitudinal force due to Wa er Surface friction and live load.

JJJ

Figure 2-31.ice pressure and Figure 2-29.Forces due to temperature rise: stream flow against pier.

2-13 transverse rotational (load) (moment)

torsional

14 transverse (reaction) axial

Figure 2-32.Forces acting on members.

unit stress, is within allowable limits, the member can withstand the applied loads and the member can be considered "safe". If, however, corrosion has reduced the effective area of the member, the intensity of the stress is increased and may exceed the allowable limit. Corrosion may also cause a notch effect which concentrates the stress and further weakens the member. b. Compression. A simple compression member could be a vertical steel column of a viaduct (fig. 2-35). Here the dead and live loads cause downward forces which produce a certain intensity of compressive stress on the entire cross section of the member. In compression members the unit stress not only has to be within allowable limits, as is the case with tension members, but the allowablestress becomes smaller as the slenderness ratio becomes greater. That is, for any given cross section, the longer the column the lower the allowable stress in compression. This is because long compression members will buckle rat ter than crush. c. Shear. Transverse forces exert a shearing forr,e-sv tendency to slide the part of a member COMPRESSION to one side of a cross section transversely with TENSION respect to the part of the member on the other Figure 2-33.Axial forces and stress distribution. 2-14 side of the section. This scissor-like action is seen that the four shear stresses will combine to illustrated in figure 2-36. Oddly enough, the real form a tensile stress. While this is the most likely shear stress produced by a transverse load is source of shear problems, most design criteria manifested in a horizontal shear stress (fig. 2-37 consider vertical sheaar as the criterion for shear (a)). However, it is accompanied by a vertical strength. The formula for vertical shear stress is: shear stress of equal magnitude as shown in V figure 237(b), which is an enlargement of the little element of figure 2-37(a). It can easily be where:fy = unit shear stress V = vertical shear due to external loads A. = area of web.

Figure 2-34.Truss sub-vertical in tension.. Figure 2-35.Steel viaduct column in compression. Transverse Load

OM%- .1=111=1. ------oll Shear Plane

Figure 2-36.Shear forces.

2-15 d. Rotational Force. A rotational force or mo- axis. This action is illustrated in figure 2-38. Note ment exerts a turning or bending effect on a that the stresses are greatest at the upper and member in the plane of the member, and may be lower beam surfaces and decline linearly to zero considered as a force acting at the end of a rigid at the neutral axis. The maximum flexural (or stick. The units of a moment are the product ofa bending, of fiber) stresses are calculated by the force and a distance (or arm). These may be following formula: pound-inches, pound-feet,kip-inches,kip-feet, Mc etc. When an 'external moment is applied to a it' I beam or member, an internal resisting moment is developed. This internal moment is formed by where: fb = bending stress longitudinal compressive and tensile fiber stresses M =moment throughout the beam, acting about the neutral c = distance from neutral axis to extreme fiber (or surface) of beam T!cal Horizontal I = moment of inertiaa property of hearinglane the beam cross sectional area and Load shape. Pim. stresses at points between the neutral axis and the extreme fiber, use the distance from the neutral axis to the point in question rather than "c." While bending occurs in many structures, it is most common in beam and girder spans. The most common use of a beam is in a simple span. A simple span could be a timber, concrete, or Figure 2-37a.Horizontal shear. steel beam supported on abutments at each end. The dead and live loads cause downward forces Shear Stresses which, with the reactions form external moments, Result ant result in the bending of the beam between its T I supports. The bending produces compressive stresses in the upper, or concave, portion of the beam and tensile stresses in the lower or convex portion of the beam(fig.2-39). A moment producing this type of bending isconsidered positive. Positive moment is typical of vertical Figure 2-37b.Shear stress and diagonal tension. loads acting on simple beams.

Compression Face

Tension Face L_ ben ding lengthened stresses Figure 2-38.Bending stress in a beam. 2-16 Live Load 71 Figure 2-39.Simple beam bending moment and shear.

A continuous(over intermediate supports) mentary analysis of a bc 1.m, the points of primary beam is shown in figure. 2-16. It is apparent that interestare loads, reactions (support forces), the same type of loading will produce a positive shears, and moments. The following examples will moment acting on the middle of the span. How- indicate the procedure followed in determining ever, over the support, the upper part of the beam the values of reactions, shears, and moments. will elongate while the lower part will shorten. b.Reactions.Consider the beam in figure2-40 This is called negative moment and is present in (a). It has span L, load P, and cross sectional area continuous structures. A negative moment can of bd. The reactions due to load P will depend also be produced in a simple beam (fig.2-14)by upon the size and location of the load, being an uplift force. inversely proportional to the distance between the In addition to these horizontal fiber stresses, the load and the support. Using the law of the lever, vertical loads on the structure are carried to the the left reaction, R Lis found to be equal to a) reactions at the span ends by means of shearing in figure2-40(b). Where more loads than stress in the web of the beam. The beam must, of P(LL course, be sized so that all the stresses which it is one are involved, the reactions may be calculated to withstand will be within allowable limits. It is for each load separately and then totaled(fig. also important that the beam be rigid enough to 2-40(c)).When a uniformly distributed load is used keep its deflection within proper limits even when as in figure2-43(a), the load can be considered to be the stresses do not approach limiting values. a series of point loads of w pounds applied every foot. The reactions may be obtained by calculating 2-3.4 Calculations. the total distributed load, W =wL, assuming it concentrated in a single load at the center of the a.General.In calculating the simple moments, total distributed load, and proceeding as before. shears, and axial forces of a beam or truss, the The formulae for reaction may be summarized: analysis is governed by the basic laws of statics: P(La), Pa ZIT =0 R L = RR = for concentrated load ZH=0 wL EM =0 R L = RR = for uniformly distributed loads 2 where: V = vertical forces H = horizontal forces After calculating the end reactions of a beam, the M = moments. results may be checked by use of the basic law of statics: While such terms as "moment", "shear", and ZV = 0 "reaction" may be new, their characteristics ar. implicitly used by the layman whenever he deals where there are no external horizontal or moment with a lever. Actually, the laws of the lever are loads involved. Adding the load and reactions it special cases of beam statics. In making a rudi- can be seen that in figure2-40(b):

2-17 ZV=0=P+RL+RR= P+P(La)Pa For computational purposes, forces upward ( ) +L, and to the right (-) and clockwise moments (re) P(La+a)=p+p=0 are taken as positive. This same relationship is V= P+ used in finding internal vertical shears. a 1 -a 1.4Poarwtcithl. 1 Left Right Reaction = it RR Reaction 5 an (a) a P I.-

P(L.-4 L RR = Ea T. (b)

a, CI,

(L- a zkt RR.=p,a, L as

= ft CIL L cia

P1R

RL=RL,tka= lia.- as) t Pa(1.-4:10 ea, + ila.RR,* RR2 =RR 1L L L L-4 (c) Figure 2-40.Reactions with concentrated load applied. 2-18 c. Vertical Shear. Vertical shears may be ob- where: V1= shear force et x1, i.e., a vertical force tainedina somewhat similar fashion since transverse to a horizontal beam. reactions are actually the end (and the maximum) shears on a beam. If imaginary (orvirtual) The astute observer will note that this creates an P(L -a)x1, cuts are made in several places in the beam unbalanced moment of but considera- of figure2-40(b), say at xi and x2 as shown in figure2-41(a),itisdividedinto three tion of that aspect will be deferred. When checking "free bodies". A free body is a portion ofa shear at x2, the free bodies [1] and [2] are usually loaded member or structure which is hypotheti- combined as in figure2-41(b), since there is now cally separated from the rest of the member or no need for the joint at x1. (However, using shear structure, with the sole result of changing internal V1, free body[21alone would serve to determine forces to external forces. If a real beam were V2.) Again using ZV =0, divided into three parts, load P would be carried P(L -a) 0 = completely by new reactions at x1 and x2, and the P-I-V2 original reactions RL and RR would becomezero. V2-P -P(L -a)PL -PL +Pa Pa However, the free body concept requires theuse L L of equal and opposite reactions atx1 and x2, allowing load P to reach reactions RL and RR. It will be noted that V2 could have been calculated The important thing, however, isthat these from free body [31 also. Once again, we note the intermediate reactions are actually the internal presence of an unbalanced moment and defer its vertical shears. Therefore, considering free body consideration. A similar approach is used in deal- (1) in figure2-41(a) the shear at x1 is found from ing with distributed loads. First, determine the the V =0 law, i.e., reaction as done above, then, cut the beam at point x/ creating free body [1](fig.2-43 MV =0 =RL-V1 (b)). The total distributed load on this free body iswx1 P(L-a) and it is concentrated at the center of the free L body. Again:

R= P L

® IIN/2-7P-P(L-a Pct (L-(2) E x2 L L 1. (3) Figure 2-41.Shear forces with concentrated load applied.

2-19 P (L-a) Pa L (a)

P Ma= PQ -11:42Xa

P (1-- ca xa. 1(1Viz Pa Pa L (b) L L IP PCL-42) it Pa :: P a T. L- a

1 ti- © P L- I )1(Mt;Pa (L-a) L -C- (c) a P

1 0 } T- P (L.- cl) I., a I V=Pa (d)1. Figure 2-42. Moments with concentrated load applied.

2-20 ZV =0 -=RL- Wi- v wL, = 2-wxi-Vi

wL V1= -wx =w( xi) The final step in moment calculation will be cal- 2 2 culation of the moment under a load. This isa special case of the foregoing calculations, butan In this case, V1 may be a minus value, if the reac- important one, since maximum moment is usually tion is less than wx1. This would mean that the at a load point. In figure 2-42(c), P is divided into direction of the shear is opposite to that assumed, two parts proportioned to the two reactions. The and actually is an upward force. moment under the load, from moments taken d. Moments. In the above determination of about the left support, is shears,thepresence of unbalanced moments P(L -a) acting on the free bodies was noted. These mo- ZM Left =0= a M=0 ments are important since the beam must be designed to resist them. Figure 2-42 (a) shows Pa the same beam with free bodies [1], [2], and [3]. M = (L -a) In free body [1], applying M =0, it is obvious that an internal moment at x1 is required. Moment M1 If a the special ease of a point load at mid must be opposite in direction to the moment ' formed by the reaction RL and the vertical shear V. These forces create a moment about the ]eft span exists and P(L -a) support of xi. M=Pn(L-I)=!(14)=-13-1E 2 2 2 2 4 P(L -a) XMLeft =0=170(1MI= XI M, This calculation can also be made about the left P(L -a) support. It may also be demonstrated as in figure M L )(1 2-42 (d): In figure 2-42 (b), the moment is calculated at x2, Pa by again taking moments about the left support =0=RL-1-1+VL(L -a) -P-EV = --+V (x2 could have been used equally well): Pa L ZMLefi =0 =Pa -V2x2- M2=Pa Pa--x2-M2 ZM Left = 0 = (P --EPa)a - M -/PL L-Pa )\a M2 = Pa Pax2 = Pa(1 - -M =(LPa -a) -M The distributed load is handled in a similar man- Pa ner (fig. 2-43 (c)). Taking moments about the M = (L -a) left support: L

M1=0 =WXI(MXI) CIX1-341=WX1(1/2X1) e. Shear and Moment Diagrams.

WL ) X (1) In making calculations for checking a (WX1--TiM1=W12TWX12 beam, it is often convenient to use shear and moment diagrams. A shear diagram for a beam is WLX1 WX12 la +WLX1M 1 = a curve, or graphic plot, in which the abscissae 2 2 2 Ivil represent distances along the beam, and the ordi- wLxiwx12..rrw_xi(L-xi) nates represent the vertical shears for the sections ***MI 2 2 at which the ordinates are drawn. The moment diagram for a beam is also a curve in which the In the special case where x1= 2 abscissae represent distances along the beam, but the ordinates represent the bending moments for 2-21 the section at which the ordinates are drawn. In tion of the beam to the left of the section under constructing these diagrams certain conventions consideration. The remaining part of the beam and relationships are useful. The relationships will (on the right of the section) will have a rela- not be derived here. Those who are interested can tive downward movement. In figure 2-36, the find both derivation, proof, and more detailed shear at the illustrated section is positive by instructions in standard texts on structural analysis this convention. In figure 2-41(a), the shear is and design. positive at x,, and uegative at xo. For the mo- (2) The sign conventions for shear diagrams ment diagram, the moment convention will be will be similar to that maintained in paragraph that mentioned in paragraph 2-3.3.d. A posi- 2-3.4.b, i.e., forces upward () and to the tive moment bends a beam into a concave up- right (-t-) are considered positive. Shears are ward shape, while a negative moment causes a positire when the external forces or loads pro- concave downward curvature (fig. 2-44). It .duce a relative upward movement of the por- may be observed that all moments shown in ct:::i 1 W= wL w *ift.

RR= wL CEO .Tvul- 2.

WC"W Xi I X w*/ft./

I IC 1111111111111111i

wL=RL wLwxa wL 2 2 XI 111. (b)

= I II xi ± 1 Netri wx,( L xi) w /ft.

lAtitr4wL wx, RR= WI- 2 z. (C)

Figure 2-43.Reactions, shears, and moments with uniform load applied.

2-22 figures 2-38, 2-39, 2-40, 2-41, 2-42, and 2-43 ((t) positive convention for moment given in are positive. As noted earlier, the concave up- paragraph 2 -3.4.b should be used for calcula- ward slope of the positive moment is due to tions only. In plotting moments, it is customary compressive shortening of the portionofthe to plot moments on the surface of the beam beam above the neutral axis, and tensile elonga- which is in tension. This gives an excellent tion of the beam below the neutral axis. (Nega- graphic representation and helps to avoid er- tive moment is just opposite.) The clockwise rors in sign.

Concave Surface Upward

ressive face

face (a)PositiveMoment

tensile face

Concave Surface Downward (b)Negative Moment Figure 2-44.Moment convention. The curvature is greatly exaggerated for clarity. The shear forces are actually nearly parallel to the loads. RL = 12k ( 21.4) (L- Cid 4. P2 (1-- +1k( 7.4') = 6.42k+ (32) 0.56k = 6.98k 8 . 0 2 k RRR = R = 40' 5.58k+ + 2.44k a2= 8.040' 2k = 1 2 k (18.61) + (32. 6s)= = 6.98k = Va, (a) o cling Vt.VG, = RL= VL + 6.98k = RL PI 11 V01 a 6.98k- 12k -5.02k aftO V,32VR=Vat = =Va2=Va, - 5. t Pe- 8.0 RL+ 02k - 3k = 2k Pi + - 8,02k (b) She r - 5.02k V VR + RR = 02k 4. 8.02k =0 MEMc.Ma, = == M014- Vi a,= Va, 6.98k(18.6')= 129.8" 0415.0 2k( 1.41)* 1 2 2. 8 1298kf kf Mai= 128.8 Mc= 12 2 . 8 kf 5kf MftMaeM02: a "C. Ma2+g122.8kf V020-- 5.02k (12.61 Vq. (12.6) 02) 5 9.5kf 1 (c)Figure 2-45. Shear and moment diagrams for concentratedtvioment loads. MR=MR ", 0 595k - 8.02k( 74)= 59,5k- 59.5k (3) The following simple relationship pro- Va= RI,- 6.98K, and vides an automatic and easy way of crputing V,,,=RL-FP,,--- 6.98K -12.00K -5.02K shear and moment diagrams. (a) The shear ordinate at any section is The algebraic difference of the two shears should equal to the algebraic sum of all the vertical loads equal the concentrated load, P1. The shear re- to the left of the given section. mains unchanged for the next 14'; therefore, the (b) The moment ordinate is equal to the shear diagram from X =18.6' to X =32.6' is a net area under the shear diagram for the portion horizontal line at V= - 5.02K. At X = a2 = 32.6', of the beam to the left of the section. the presence of load P2 is marked by a negative vector of 3K. This causes a further increase in (4) Shear and moment diagrams and calcu- negative shear since: lations for both concentrated and distributed loads are illustrated in figures 2-45, 2-46, and Va,=Va,-1-P2=RL-I-Pi 6.98K -12K-3K 2-47'. While these figures are intended to be self- explanatory, some clarification may be helpful. V, = V., -1-?2= 6.98K - 12K -3K = -8.02K Beam and loadings similar to those in figures While there are two different values of Vat at 2-40 (c) and 2-43 (a), but with specific numerical X = a2, there is not as much concern since the values, are used in figures 2-45 and 2-46. The sign does not change. In such situations, the loading, in which P2=12", P2 ^3K, and w =1k/ft, larger numerical value isof primary concern. is comparable to that of the wheels of an H-15 Since there are no more external vertical loads to truck and to the dead load of a steel beam cope with, the shear diagram continueshorizon- bridge. The dimensions are also similar to what tally at -8.02K to the-right support. The right would be encountered in a bridge beam design. reaction of 8.02K is equal and opposite to the In figure 2-45(a), the reactions are calculated shear; therefore, the diagram is correctly plotted. using formulae developed in figure 2-40 (c). As a The reaction vector RR =8.02K closes the shear check on the calculation, diagram and satisfies the requirements of static V=0=RL+RR-P1-P2=6.98+8.02-12-3 =0 equilibrium: V= O. The general formula for shear at any point, X, on a beam may be given Consistent with the nature of a shear load, the as follows: end shear VL occurs an infinitesimal distance to the right of the support. However, the algebraic Vx =RL+ZPx operation treats it as being at the supports. where: V= vertical shear at X (5) Now calculations of the shear diagram R L = left reaction can begin. The leftmost load is the leftreaction, 213x = algebraic sum of all external loads which is equal to the end shear: acting on the beam between the left VL = RL = 6.98K. reaction and section X. (6) While the moment curve values can be The upward end of the reaction vector R marks calculated directly from the loads, calculation of the first point on the shear diagram (X =0, the moment diagram from the shear diagram V =6.98K). Since no further vertical forces are provides better visualization and helps to avoid encountered until P1 is reached, the vertical errors. In figuring moments, the secondprinciple, shear is constant and the shear diagram is a mentioned in subparagraph (3) (a) above will horizontal line extending to the right for 18,6'. At be used, i.e., moment value is equal to the net this point on the beam, P1 is applied as noted by area under the corresponding length of shear the downward 12" load vector. Note that P, curve. Since the beam is simply supported, the takes the shear diagram across the X-axis and moment is zero (0) at the supports. changes the shear to a negative value. Here, the fine distinction as to application of a shear force NIL =O at an infinitesimal distance from the section is important. Just to the left of X =al, the shear is Calculating the moment at X = a, = 18.6', (under positive and equal to 6.98K. Just to the right of load P1), the area under the shear diagram is X =a1, the shear is negative and equal to -5.02K, Vaal) = 6.98K (18.6') = 129.8K F 2-25 =129.8K F The fact that MR returns to zero (0) checks the The moment at X =a2=1\11:-FV.,(a2-al) arithmetic by verifying the static equilibrium equation, IM =0. = 129.8K F 5.02K(14') (7) For a uniformly distributed load, such as -129.8K F 70.31°' = 59 .5KF dead load, the shear and moment diagrams will The - 5.02K(14') will be recognized as the area always be of the same general shape. The shear under the shear curve between X =al and X= a2. diagram is a sloping line crossing the X-axis at Since it is a negative shear area, the moment is midspan and the moment diagram is a parabola. reduced. Calculating the last area under the shear The only variations will be in magnitude. With diagram between X= a 2 and X =L: the same 40-foot beam as in figure 2-45(a), the point loads are replaced with a distributed load MR =Ma,+ V,(L = 59.5K F -8.02K(7.4') of w =1 k/ft. in figure 2-46. The reaction, cal- =59.5K F _59.5KF =0 culated from the formulas oil figure 2-43 (a) are:

= 32.6' L-02.- 74'

RI.* RR :=W.L r. 1 k (40)= 20k 2 tt

V L.= RL=20k Vx= RL- K

Val r-*2 0 1 (18.6'1 =1.4

Vi= 20K- 4(1(201) = 0 Va2 = 20K- If(32.6') = -12.6K VR = 2 0K- ( 40= - 20K

VR+R R'a2 OK +20k= 0

Ma, = m + n=1.41(.08.0 + ( 20- 1.4)k8. 04 Mop= 2 6 + I73= 199 Mt= m+n+p=199kf+14k(1.4q

0.6k M(t. =19910 + 1.0kf =200kf k Mat - q=200 -12.6(12.61)-k Mai =199 C..

1 (c) Moment MG2 = 200kf-79.4kf= 120. 6kf MR= M02- r -s

MR= I20.6kf -I2.6k (TAO- 7.4k (7.41)± MR= 120.6kf-93,211f- 27.4 kf = 0 Figure 2-46. Shear and moment dcagrams for uniform loads. 2-26 RL=RRw 1 2 /ft.(40') =20K between X = a2 and the right support is added to 2 2 M., and The end shear is again equal to the left reaction, (7.4K)(7.4') MR = 120.6K F(12.6K)7.4' VL=RL = 20K. The shear at any point on the 2 beam may be calculated by the formula shown in figures 2-43(b) and 2-43(c), i.e., MR "=-- 120.6" - 93.2K F -27.4" = 0 wL as it should be. Vx =--wX or RL wX. 2 (8) In figure 2-47, the distributed load and Figuring the shear for the same points X =al and concentrated loads are combined. The figures X = a2, as well as at midspan, the shears are as may be obtained by superposition or simply add- shown in figure 2-46(b). ing the reactions, shears, grid moments at the corresponding section. While the shear and mo- 1.4K, = 0, V.,= 12.6K ments can be obtained from the combined loads 1k f(40') directly, it is suggested that the loads be treated At the right support, VR = 20K 20K separately until some proficiency in this type of which is again equal and opposite to RE. The calculationshas been acquired. Attentionis moment curveisfiguredeither by applying called to the fact that maximum shear occurs at the formula Mx = Mwx(Lx) given on figure the supports and that maximum moment occurs 2-43(c), or by adding the areas under the shear at the section where the vertical shear diagram diagram. (The latter will be done in this illustra- passes thru zero. The set of sample calculations tion). ML = 0, of course, and M., is obtained by cal- presented in figures 2-45 and 2-46 is intended to culating the trapezoidal area between X =0 and give a unified demonstration of the procedure. It X = a1= 18.6'. The trapezoidal area is divided into should be noted that non-uniform distributed rectangle "n" and a triangle "m" as shown in loads are often encountered in actual practice, Figrre 2-46(b). and that the live loads represented by the con- 2) r_-199KF centrated loads can change position. For the H M., = 1.4K(18.6')(18.6K) (18.6') (Y truck, the position used in figure 2-45 produces At midspan where X =20', the moment is the maximum moment, but not maximum shear. A moment at X =a1 plus the area of the small different truck will produce maximum moments triangle "p" between X =ai and midspan. at another location on the beam. M = 199KP+1.4K(1.4')1/2 =199K F+0.981 F= 200" f. There is no doubt that many questions have At X = a2, the moment is reduced by the area of been left unanswered by this brief exposition. the triangle "q" between midspan and X =a2; or Such topics as torsion, negative moment, and mov- Ma,= 200K F12.6K (12.6')1 /2 ing loads have 'lot been discussed. It is expected = 2001'F-79.4" =120.6KF that the instrJetr,r will amplify the foregoing discussion to the extent that the needs and the Finally the area of the trapezoid ("r"+"s") interest of the trainees dictate.

2-27 a2::7: j41

wir

2 8.0 2k

0 co r.-176 CV I1 a2 V =-20.62k ar

(b) Sh 28.02K

=op

80.1kf

N61=328.8 M 3 2 2. 814 (c) Moment Figure 2-47.Shear and moment diagrams for both concentrated and uniform loads.

2-28 CHAPTER III

BRIDGE INSPECTION REPORTING SYSTEM

Section 1. INTRODUCTION system is to have trained and experienced per sonnel record objective and subjective observa- 3-1.1 General. tions of all elements of a bridge structure and A good bridge inspection reporting system is to make logical deductions and conclusions from essential in order to protect the lives of the their observations. The bridge inspection report public and to protect the public's investment in should represent a systematic inventory of the bridge structures. It is, therefore, essential that current condition of all bridge members and bridge inspection reports be clear and complete, their possible future weaknesses. Moreover, since they are an integral part of the lifelong bridge reports form the basis for quantifying record file of the bridge. While a number of the manpower, equipment, materials, and funds states have for years had a reporting system that are necessary to maintain the integrity of for bridge inspections, the reporting systems the structure. have been almost unique to each individual state. Moreover, information contained in many 3-1.3 Requirements. reports has unfortunately not always been sufficient nor has it been in a form suitable for The requirements of a good field reporting sys- analysis' and evaluation from both a qualitative tem are : and quantitative standpoint. In a number of a. A thorough study of all available historical states, the bridge reporting system must be for- information on the structure including design mulated and designed :o that report informa- and/or "asbuilt"plans,field and design tion can be analyzed and evaluated, to a large changes, foundation information, records of extent, by electronic data processing means. previous inspections, and any other available This requirement is because of the large num- information relative to the structure. ber of bridge structures located within those states. Because of the requirements that must b. Information on repairs performed and re- be fulfilled by the National Bridge Inspection construction work completed on the structure. Standards, it is necessary to employ a uniform c. Current bridge inventory information. bridge inspection reporting system. A uniform d. A procedure for making the inspection of a reporting system is essential in evaluating cor- structure. rectly and efficiently the condition of all structures. Furthermore, it will be a valuable aid in e. An inspection recording system. determining maintenancepriorities,replace- (1) A notebook format. ment priorities, structure capacity, and the cost (2) Standard forms. of maintaining the nation's bridges. The infor- (3) Notebook and standard forms. mation necessary to make these determinations f. A standard notation system for indicating must come largely from the bridge inspection the condition of the various elements or mem- reporting syStem. Consequently, the importance of the reporting system cannot be over empha- bers. sized. The success of any bridge inspection pro- g. Sketches and drawings of members and gram is dependent upon its reporting system. components that are to be inspected. h. A standard nomenclature for bridge ele- 3-1.2. Purpose. ments and members and the components made The purpose of the bridge inspection reporting up of these members. 3-1 i. A summary sheet. (b) Inspections for gathering informa- (1) Qualitative condition of the structure tion for possible reconstruction or replacement. in general. (c) Inspections for routing overweight (2) A quantitative summary. vehicles. (a) Work needed by priority and its cost. 3-2.2 Scheduling. (b) Total cost of all repairs. A schedule should be developed for all types of j. A provision for specialist reports such as inspections. The schedule should be followed as structural, mechanical, and electrical. closely as possible to assure that all structures will be inspected within the required time span. k. A narrative summary section for short, Scheduling of any bridge inspection should be concise narrative reports of the condition of the accomplished sufficiently far in advance to perstructure. mit the coordination of manpower, equipment, 1. A section for special repair procedures that and specialist personnel. Sufficient time and might be recommended by the inspector. manpower should be allocated for the special m. A section in which the inspector gives spe- inspections that may be required. cial instructions for the repair or for further inspection of a structure. 3-2.3 Planning and Reporting the Inspection. The above items are considered to be minimal a. Genertd. Careful planning of the inspection requirements in the establi.shment of a bridge and selection of appropriate reporting for.nats reporting system which will assure complete- are essential for a well-organized, complete, and ness, uniformity, and continuity of inspection efficient inspection. During the planning phase over the years. As advancements are made and the following items should be considered: structures change, there will necessarily be re- (1) The inspection schedule. finements, but this basic content ouume should provide for the development of a system that (2) The inspection type. can be profitably used by all states fo many (3) The resources req_ired :Manpower, years to come. equipment, materials, and special instruments. (4) A study of all pertinent available information on the structure such as plans, pre- Section2. PREPARATION FOR INSPECTION vious inspections, current inventory report, and previous repairs. 3-2.1 Inspection Types. (5) The type of reporting system to be a. Routine Inspections. Routine inspections used : notebooks, standard forms, or both. shall be made on all structures at least once (6) Setting up the notebooks, including every two years. the notation system and all of the required pre- b. Interim Inspections. liminary drawings and sketches. (1)Weight-Limited Structures. Inspec- (7) Coordinating the resourcerequire- tions shall be made at least once a year on all ments, particularly that of specialist personnel structures not capable of carrying the state's and special equipment. legal load limit. (8) The inspection procedure. (2) Structurally Deficient Bridges. Struc- b. Scheduling. An inspection schedule is nec- turally deficient bridges shall be inspected as essary to assure that all structures are in- often as required to assure the safety of the spected when programmed. Detailed scheduling public and the integrity of the structure. is essential to assure that the proper manpower (3) Special Inspections. Special inspections and equipment are available when they are may be required for many reasons, some of needed. At times, the weather, stream levels which are: and seasonal traffic loads of the structure must (a) Structures damaged by accidents or be taken into consideration in scheduling the other causes. inspection.

3-2 c. Inspection Type. on the right-of-way, the right-of-wayitself, soil (;) Routine Inspection. Routine inspec- and foundation information, stream profile and tions will follow the procedures described inthe stream protection devices, and stream eleva- National Bridge Inspection Standards and tions at normal and high water levels. If the those set forth in this training manual. stream is navigable, note what navigation devices are employed. Special attention should be (2) Interim. Inspection.. paid to unusual or complex features of the (a) Weight-Limited Structures:Suffi- structure. Plans should be studied in detail to cient data must be gathered to determine what note possible critical areas of the structure. the limiting members of the structure are and Previous experience should be resorted to as a what weight limit should be prescribed. If pos- means for identifying those areas thatfre- sible, the date for any reinspection should be quently cause problems. After a thorough re- determined. Changes in the character of the view of the plans, the type of reporting format bridge traffic should be noted and recommenda- can be determined. tions concerning repairs needed to maintain the (2) Data Review. A study should be made structure at its present rating should be made. of the most recent inventory report, the newest (b)Structurally DeficientBridges. traffic data, previous inspections, repairs and Inspections should be performed as often as is reconstruction work, and any other available required to ensure the safety of the public and historical data related to the structure. the structure. The type and extent of the defi- (3) Procedure Plan. In most instances, it is ciencies of each member should be recorded in advantageous to inspect structures in the same sufficient detail to perniit the determination of sequence in which they are constructed. That is, the safe carrying capacity of the structure. Rec- the substructure foundations first, and the su- ommelidations for repairs necessary to main- perstructure next. Chapter IV includes a more tain the structure in a usable condition should detailed discussion of the inspection sequence. be submitted. (c)Special Inspection. Sufficient data f. Reporting Format. must be gathered to satisfy the specific purpose (1) Notebook. The notebook will normally of the inspection. For instance, a damaged be used as the sole reporting format on struc- structure should be closely examined both in the tures that are complex or unique. See Section damaged area and in adjacen:: areas to deter- 3-3. mine the extent of structural deterioration. (2) Standard Forms. Forms should be sufficiently flexible so as to be adaptable to most d. Resources Required. While; all needed man- structures. See Section 3-5. power, equipment, materials, andinstruments should normally be available to the inspection (3) Notebook and Standard Forms. It is sometimes advantageous to use a notebook for organizationitself,specialresourcesmay sometimes be required. Mechanical, electrical, the unique to complex portions of the structure, hydraulics, or underwater inspection specialists and standard forms for the more common will be needed for'some inspections. Special in- parts. struments such as ultrasonic measuring devices, electronic depth finders, and others may be re- Section 3. PREPARING THE INSPECTION NOTEBOOK quired.Special equipment such as additional scaffolding, "cherry pickers," and "snoopers" 3-3.1 General. may have to be obtained. When the notebook format is selected for re- e. Data Study. cording bridge inspection results, the informa- (1) The Plan Review. The review should be tion should be recorded systematically. The fol- made using "as built" plans. If the "as built" lowing describes a suggested content outline. plans are not available, design plans may be a. Title Page. The title page should contain used. The review of the structure's plans should the name of the structure, the structure identi- include a study of such environmental features fication number, the road secticn identification as the stream's channel, the flood plane,utilities number, and-the name of the crossing. The back 3-3 of the title page should be used to note the ranged sectionally in the order in which the names of the members of the inspection party, structure was built, i.e., starting with the sub- the person in charge of the party, the type of structure and ending with the superstructure. inspection, and the dates on which the inspec- The format of each section of the notebook tion was made. should be arranged so as to proceed from the b. General Format. The left-hand page should general to the specific, i.e., from a general lay- contain the name of the member being in- out of a particular unit to the details of that spected, its components, the evaluation of that unit. This applies to evaluations and to sketches member and its components, and appropriate as well. Figure 3-1 illustrates the dividing of a associative space for comments. The right-hand bridge into three main parts, and the further pag- should be reserved for sketches or draw- division of these parts. Figures 3-2 through ingsOf the member. The notebook should bear- 3-6 show the details of some of these units. /O. 61,-, dye 44- 93 -

--5-0 A-3-717-4,e forte_ , /Yo. /9454)ti'nen74 /2 -1/-- _Ace/ / z 6er2 / 3 Pier 3 44____ /3e,- f. /9 ..-so, 4607--,,ern" z 0 Solo erzsiroafore

,__p_. eir7 l .2/ Spar,2 zz pen, 4 2 g' .loor, .6- c Y._ Oe c.lc A041,7 I 32 ....5;Dob 2 a3 .....5par).3 341 al" 4,4/7...4 __.3_4 _____%37

Figure 3-1.Typical notebook index page. Division of a typical bridge into its main parts.

3-4 . 1 1 _. _.. 1 1 ! , 17--,-- .. L . . .._ .__.

_._...

iI 1 __ 1 0 ...__ -----...... ,,.. iiPF!!_ i .C.__..-: ei.,,e)...__ 1111Vb 5 5 Mill .44 .

Imo ...... ,:ti..,6 libwrii--,- : ::,,,,..._...._...... wL .1 wmminw im1 ma 11111 im,,,,,...... , ...... II 'EN .zi.... If ----iPriZ. ---. 1\111 .;:,---4.-moini AIIwo- ...... 0A SIMIMa§ZENal ni I I'

1 i -1- i

... '14 IP

I1.--.N. Le0% V 4.... 3K V 4_0 zz, e , 4) v 40 -it, 19 Cr) (ti' .. lo I vi t cti 4 0 1,,,i NI V k V U Os h '41/4 V3, r *4b %....., ZI,...; ha N N __.).%__ 1 t 0 0 ',I ....4 in

%kr Figure 3-2.Typical notebook page. Note drawing on right-hand page, and evaluation of circled elements on left-hand page.

3-5 3-3.2 Sketches. terrain obstacle layout, major utilities, and any In most cases it will be possible to insert re- other pertinent details should also be included. productions of portions of the plans in the note- h. Substructures. Sketches or drawings of book. However, in some instances sketches will each substructure unit should be included. In have to be drawn. many cases it will be sufficient to draw typical a. Overall Sketch. The first sketch Should units which identify the principal elements of schematically portray the general layout of the the substructure. Each of the elements of a sub- bridge, illustrating the structure plan and ele- structure unit should be numbered so that they vation data. The immediate area, the stream or can be cross referenced to the information ap-

/4. 43,-;d 3 3 _ /7e_c--_C.,/,'cl _ lemeotele,dii h.ty/9- AMP, Cht Meer.f i .._4_6.0.121/7 7 A Mack._Tzpiocc.

2 ic'eni.er-s, 7 --e.iitictste._ irsolece.- .5...41ce.

-1 3 Rerittni r_

dwo-- . Sc Soe),W;I:xs 4. .5,941:.07117 PertheiV0"to17

Figure 8-8.Typical notebook page. This is a left-hand page showing the evaluation of pier elements.

3-6 pearing on the data page on the left-hand side bers,floorbeams,stringers,bracing,dia- of the sketch. Items to be numbered include pil- phragms, windbracing, decks, expansion joints, ing, footings, vertical supports, lateral bracing curbs, and hand rails. of members and caps. d. Special Sketches. Additional sketches may c.Superstructures.Superstructureunits have to be prepared of critical areas of certain should be sketched both in cross section and plan bridges. and elevation views. The elements of the superstructure units should be numbered as they (1) Trusses. Critical areas of trusses in- were in the substructure units. Items to be num- clude connections from floor beams to chords, bered include bearings, main supporting mem- gusset plates at panel points, portals, cross

V .43.-r.4;(7e91-P3- 3 Span/ MC7: - tin, ElementEleApple./Alin,'/9-04/ein wo. amnx, .5-c.kil o-Reb,...: 1g1 Ar74..,..f. 6 /iv_ex,...L T,re.selee) CP .1 a_24WL'ff GColfCl A "roe SC VAWV' -1eutoiot" ,f Astef0e4 42i11 re c roj0icevcaccbt aiornty _

Figure 3-4.Typical notebook page. This is a left-hand page showing the evaluation of span ePments. 3-7 frames, damaged members, bearings, eyebars, leave blank every third or fourth page for this and heavily corroded areas. purpose. (2) Suspension Bridges. Sketches of sus- e.Alignment. A section of the notebook pension bridges should include, but not neces- should be reserved for recording the horizontal sarily be limited to, anchorages, towers, cable and vertical alignment of the structure. Align- bents, tower saddles, cable bands, suspender ment should be checked for structures that are saddles, suspender connections, and stiffening long, or show evidence of misalignment. truss connections. The critical areas on the (1) Substructure Drawings. Drawings of stiffening trusses are the same as those listed each substructure unit should include a side ele- under "Trusses" in the previous paragraph. It vation view and the two end elevation views. is particularly important to detail rocker bear- These sketches should be large enough so that ings for towers and cable bents when they exist, the structure's horizontal and vertical align- the main cable cross section, heavily corroded ment can be noted on the sketches after they members, cable bands, and cable wrappings. have been determined. (3) Swing Spans. Critical areas include (2) Superstructure. Sketches showing the truss details and connections, machinery, locks, plan and elevation views of the superstructure electrical systems, controls, and girder details are necessary. The horizontal alignment should for girder type swing spans. be noted on the plan view of the structure, and (4) Bascule Spans. The required details in- the vertical alignment of the elevation view. clude counterweights, trunnion details, locks, f. Environmental Features. The environmen- machinery, buffers, cables, controls, corroded tal features that should be included are terrain members, and details of connections of trusses features, stream profiles, high water elevation, and girders. spur dikes or other protection devices, slope (5) Vertical Lift Spans. Critical areas in- protection, channel protection, and the channel clude cables, anchorages for the cables, trun- location where it passes under the structure. in nions, sheaves, guides, limit switches, counter- some instances it is desirable to show the chan- weights, counterweight balance chains, buffers, nel condition upstream and downstream from locks, machinery, electrical system, controls, the structure. The horizontal and vertical.align- corroded members, and bearings. ment of the approach roadway should also be (6) CantileverBridges.On cantilever shown. bridges, sketches are generally required for the g. Underwater Investigation. Plots of the hinges for the suspended span, rockers, bear- contour of the stream bottom should extend to a ings, the hold-down devices,if any, in the radius of at least 100 feet from each pier. The anchor spans, truss or girder details, and the purpose of the contour plots is to determine corroded areas. the extent of the scour. On the contour draw- (7) Bearing Devices. Since bearing devices ings, a plan view of the foundation should be are a frequent source of trouble they should be included. inspected with particular care. Sketches shrduld be made of each major bearing device showing h. Specialist Reports. The final section of the its position, as in figure 3-6. Sketches should be notebook should include the reports of mechani- made of any bearing that is not functioning cal, electrical, or other specialists. properly. (8) Miscellaneous Sketches. Sketches of Section 4. STRUCTURE EVALUATION fenders, dolphins, and aerial and navigational lighting will sometimes be required. Special ter- 3-4.1 General. rain features or unusual slope protection or A bridge is typically divided into two main channelprotectionconditionswillrequire unitsthe substructure, and the superstruc- sketches. Sketches may also be required for ex- ture. For convenience the deck is sometimes pansion devices. considered as a separate unit. These basic units (9) Additional Sketches. Since additional may be divided into structural members, which, sketches may be required, it is a good practice to in turn, may be further subdivided into ele- 3-8 INIIMMUll IM nommilMm MI f 17:_ i i INIMMINIII =MUNN MN MI . Mimi. minlim.MI NM Wil 1: : .7r M1M=MEM/1=MM mi-...... 111/1 FA 111MIIMIIIIIIIIINIMMI 11111111M111 WEAMNIMINNVAIII t IIMMIIIIMIIMINNIMEMI 111_iiiirAN. 'V 111111MIII 11=1111MIIIMIIIIIIMIIIM-.101111111U/11 N El MIM11=1111111H1111111111_111IAMMIIIIIIIIIIIII :_lii:__... 1111111=111111MOMMIIIMOIN0111111M .. _ c.. .1 IIMMIIIIMIIIIIMIUMINIIIIMM111111111111== 4 __,tr.___. MMIM1111111/MIWIIMMIIMIIMMININI . 3U !sk 1 1.1=01.41rAMMIMMOMNIARKEIVIWY111111...... _...... , r ..,_...... _ f'NCI IMIMIMIN1111111111111111111111M1r"71/11111W MAIa* A _.___ 1_ NI issmirAmmelmisA. =or rm. . a . M1141011Mmiramilliara W.4 . hisrmmommwaliwaim r. a 41111111IM 7-1:- au AIM As? IMIIIIIIMMIIIIINEW.W111111VIM Alelm....mr.11111111111111V -".)I 1111111111MMINIVAINIIWIEMImra moormem Alma C. malmoinms mural All1=1111MNIAIIIIIMI td IIIIIIIIIU1111=w2M11___....,_-_--..mw...... 111v4ismm_____ =MEMEL" WW1MI=.rAINII11111MP NM Fa 1 II P71/1 1 111=1111NIM r EN...... -a._ mial =mum= Nam= _ wil mom= ImmomNum mumommg immum INIIIIENIMMINWSINNWIMINI MOM IMmiM 11111i1JWIZA=J1111111 MIMI MIME IIIIIMMIIIIIIIIIIMMI IMIIMIoom ima IMINNE11111111111=1ollemul immi I. ..=maw momism L'IMEANI .:i

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Figure 8-5.Typical notebook page. Members are coded by letter and number to permit easy identification.

3-9 MIN 11111MNIMIE11111111111 li 111111M _1-- n

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Figure 8 -6.Typical notebook page. Elements of bearings are identified and rated. Note that location of bearing is also included.

3-10 ments or components. The general procedure b. Photographs. Photographs will be of great for evaluating a structure is to assign a numeri- assistance to anyone who is reviewing reports cal rating to the condition of each element or on bridge structures. It is particularly recom- component of the main units. These ratings mended that pictures be taken of any problem may be combined to obtain a numerical value areas that cannot be completely explained by a for the overall condition of a member or of a narrative description. It is better to take sev- unit. eral photographs that may be unessential than to omit one that would preclude misinterpre- tation 3-4.2 Numerical Evaluation. misunderstanding of the report. At least two photographs of very structure should Numerical ratings of bridge components are be taken. One of these should depict the struc- useful for the evaluation of the bridge. It is not ture from the roadway while the other photo mandatory for the bridge inspector to make nu- should be a view of the side elevation. merical ratings unless so instructed. However, if he desires to assign numerical ratings, he c. Summary. An inspection is not complete should follow therating system explained until a narrative summary of the condition of below. Note that ratings "0," "1," "2," "3," "4," the structure has been written. and "6" apply only to major components and d. Recommendations. The inspector should elements. The recommended rating system is as list according to urgency any repairs that are follows : necessary to maintain structural integrity and a. "9"new condition. public safety. Recommendations are discussed b. "8"good conditionno repairs neces- in greater detail in Chapter VI. sary. c. "7"minor items in need of repairs by Section 5. STANDARD FORMS maintenance forces. 3-5.1 General. d. "6"major items in need of repairs by maintenance forces. On large or complex bridges, the notebook format must be used to record inspection results. e. "5" major repairs contract needs to be However, for small and simple bridges, it may let. be more convenient to use standard forms (figs. f. "4"minimum adequacy to tolerate pres- 3-7(a), 3 -7(b), and 8-7(c) ; the forms shoWn ent trafficimmediate rehabilitation necessary represent an amplification of the condition rat- to keep open. ing section contained in the Structure Inven- g. "3"inadequacy to tolerate present heavy tory & Appraisal Sheet from the A.A.S.H.O. loadwarrants closing bridge to trucks. "ManualforMaintenanceInspectionof Bridges"). Whcn using standard forms, the h. "2".=inadequacy to tolerate any live load evaluation numbers and comments may be re- warrants closing bridge to all traffic. corded exactly as described in Section 3-4 for i. "1"bridge repairable, if desirable to re- notebooks. The reverse side of the forms can be open to traffic. used for drawing sketches and for additional j. "0"bridge conditions beyond repair comments. danger of immediate collapse. Ifavailable,standard preparedsketches should be attached to the forms with the coding ofallmembersclearlyindicated.Where 3-4.3 Explanatory Aids. sketches and narrative descriptions cannot fully a. Narrative Descriptions. Descriptions of describe the deficiency or defect, photographs the condition should be as clear and concise as should be taken and should be referenced appro-- possible. Completeness, however, is essential. priately in tl" narrative. All items on the forms Therefore, narrative reports of moderate length shown in figures 3-7(a), 3-7(b), and 3-7(c) will sometimes be required to adequately report may not always be filledout. Prior to the on bridge conditions. inspection, it should be determined which items 3-11 BRIDGE INSPECTION REPORT Bridge No. Bridge Type Inspector Name CrossingOver Under Date Year Built District County Photographs

CONDITION Field Book No. RATING --REMARKS [561 DECK 1. Wearing Surface 2. Deck - Structural Cor-dtior. 3. Curbs 4. Median 5. Sidewalks 6. Parapet 7. Railing 8. Paint 9. Drains 10. Lighting Standards 11. Utilitts 12. Joint Leakage 13. Expansion Joints or Devices 14. Record Elevations Gutterline @ 47-grgs t Spans

Inspectors Condition Rating

5?[SUPERSTRUCTURE 1. Bearing Darai 2. Stringers 3. Girder or Beams 4. Floor Beams 5. Trusses- General - Portals - Bracing 6. Paint 7. Machinery (Movable Spans) 8. Rivets or Bolts 9. Welds - Cracks 10. Rust 11. Timber Decay 12. Concrete Cracking 13. Collision Damage 14. Deflection underload 15. Alignment of Members 16. Vibrations underload

Inspectors Condition Rating

Figure 3-7(a)First pageofa typical bridge inspection form.

3-12 Bridge No. (continued)

CONDITION RATING REMARKS 601SUBSTRUCTURE 1. Abutments - Wings - 13ackwall - Footing - Pips - Erosion - Settlement 2. Piers or Bents - Caps - Column - Footing Piles - Scour - Settlement 3. Pile Bents 4.Concrete Cracking or Spalling 5.Steel Corrosion 6. Timber Decay, etc. 7. Debris on Seats 8. Paint 9. Collision Damage

Inspectors Condition Rating

6/CHANNEL & CHANNEL PROTECTION 1. Channel Scour 2. Embankment Erosion 3. Drift it. Vegetation 5.Channel Change 6. Fender System 7. Spur Dikes & Jetties 8. Rip Rap 9. Adequacy of Opening

Inspectors Condition Rating

[62CULVERT & RETAINING WALLS 1. Barrel Concrete Steel Timber 2. Headwall 3. Cutoff Wall it. Adequacy 5.Debris

Inspectors Condition Rating

rigure 9-7(b).Second page of a typical bridge inspection form.

3-13 are not applicable for the bridge to bein- of the various bridge elements on the forms. spected. The inspector is encouraged, but not Nevertheless, he is required to describe their required, to make numerical evaluation ratings condition.

Bridge No. (continued)

CONDITION RATING REMARKS

63ESTIMATED REMAINING LIFE Inspectors appraisal of structural condition of structure

OPERATING RATING

65APPROACH ROADWAY 1. Alignment 2. Approach Slab 3. Relief Joints 4.Approach-Guardrail -Pavement -Embankment 5.Signing - Legibility and Visibility 6. Record posted load limits if any. Inspectors Condition Rating

66 INVENTORY RATING

Figure 3-7(c).Third page of a typical bridge inspection form.

3-14 CHAPTER IV

INSPECTION PROCEDURES

Section I. SEQUENCE OF INSPECTION (b) Fenders (c) Scour protection 4-1.1 General. (d) Piers The development of a sequence for the inspec- (e) Abutments tion of a bridge is important since it actually (f) Skewbacks outlines the plan for inspection. A well con- (g) Anchorages structed sequence will provide a working guide (h) Footings for the inspector and insure a systematic and thorough inspection. (2) Superstructure units (a) Main supporting members a. Factors. Some of the factors that influence the procedure or sequence of a bridge inspection (b) Bearings are : (c) Secondary members and bracing (1) Size of the bridge (d) Utilities (2) Complexity of the bridge (e) Deckincluding roadway and joints (3) Traffic density (f) End dams (4) Availability of specialists (g) Sidewalks and railings (5) Availability of special equipment. (3) Miscellaneous (6) Preferences of the inspecting agency (a) Approaches b. Thoroughness of Inspection. Thoroughness (b) Lighting is as important as the sequence of inspection. (c) Signing Particular attention should be given to : (d) Electrical (1) Structurally important members (e) Barriers, gates, and other traffic (2) Members most susceptible to deterio- control devices ration or damage b. Large Bridges. While the sequence of c. Visual Inspection. Dirt and debris must be inspection for large bridges will generally be removed to permit visual observation and pre- the same as for smaller bridges, exceptions may cise measurement. Careful visual inspection occur in the following situations : should be supplemented by appropriate special (1) Flazanis. Climbing and other hazard- devices and techniques. Use of closed circuit tel- ous tasks should be accomplished while the evision, photography, and mirrors will increase inspector is fully alert. visual access to many bridge components. (2) Weather. Wind, extreme temperatures, rain, or snow may force the postponement of 4-1.2 Inspection Sequence. hazardous activities such as climbing, diving, or a. Average Bridges. For brides of average water-borne operations. length and complexity,itisconvenientto (3) Traffic. Median barriers, decks, deck conduct the inspection inthe following se- joints, traffic control devices, and approaches quence: should be inspected in daylight during periods (1) Substructure units of relatively light traffic to ensure inspector (a) Piles safety and to avoid the disruption of traffic.

4-1 (4)InspectionParty Size. When the adding more radial and tangential lines to the inspection party is large, several different tasks pattern. The reference marks on the pier should may be performed simultaneously by different be carefully defined so that they can be found or inspectors or groups of inspectors. reestablished in subsequent inspections. This will permit compilation of a good, long-term record or scour development and slope protec- Section 2. SYSTEMATIC INSPECTION PROCEDURES tion deterioration. Soundings may be made from a boat with a rod, a weighted line, or elec- 4-2.1 General. tronic equipment. Each of these methods has its Inspection of each part of the structure should limitations : be planned and outlined in detail to avoid over- (1) A rod is useful for shallow depths sights. Inspection results should provide com- only. prehensive records of bridge deterioration over (2) A weighted line is difficult to use in a a period of time. Such records are a source of swift current. .14 reference for future analyses and study pur- (3) Electronicequipmentisunreliable poses. Check list techniques should be employed where the bottom is shallow, rocky, irregular, to preclude the possibility of any bridge compo- or close to the pier. nent being overlooked during the course of inspection. For example, panel points or control c. Framed Bent or Pile Bent Piers. List each points labeled for inspection in the field book, pier and identify each column or pile by a num- should also be marked with paint or crayon on ber or letter. the corresponding points of the structure dur- d. Bearings. After the inspection of piers, the ing inspection. This is especially important on bearingsof the superstructure may be inlarge and complex structures. Once the sequence spected, if convenient. of inspection of a bridge has been established, e. Cracks and Spalls. Note location, size, and it then becomes necessary to identify those items extent of cracks, spalls, scaling, and joint mo ve- that must be inspected. The material that fol- ments of substructure members, as discussed in lows discusses the principal elements of such a Chapter V. process. f. Piles. All piles should be inspected both 4 -2.2 Substructure. above and below the waterline. a. Piers, Abutments, and Bents. All piers, abutments, and bents should be surveyed with 4-2.3 Superstructure. respect to both horizontal and vertical dimen- a. Main Supporting Members. Inspection of sions and the data compared with the "as built" main supporting members should be particu- plans, if available. larly thorough since their failure could cause b. Scour and Slope Protection. Make guide the collapse of the bridge. Main supporting marks with keel or paint on the pier cap, pier members may include, but not necessarily be face, or abutment face, as the case maybe. (The limited to, the following: location of these marks should be noted care- Main girders and stringers fully in a sketch on the inspection form or in Box girders the field book.) T-beams Move away from the mark on a pier along a Trusses radial or perpendicular and take soundings at Hangers and cables fixed intervals, e.g., 20 feet or 25 feet, up to a Eyebars minimum radius of 100 feet. Repeating this Arch ribs procedure at each mark will result in a grid-like pattern of soundings of river bottom elevations Frames (fig. 4-1). For very long piers, or those where Suspension cables serious scour is detected, additional measure- Main slabs. ments may be made at intermediate points by Floor beams 4-2 b. Drawings. If "as built" drawings or design stresses are usually marked minus (), and drawings are available, study "Stress Sheets" tensile stresses are marked plus (+), except on carefully, noting which members are :n com- some arches or older bridges where the signs pression and which are in tension. Compressive are reversed for convenience.

(a) CircularPier

(b) RectangularPier

Figure 4-1.Typical grid for soundings.

4-3 c. Coding. Numbers or letters should be as- overstressing. Note the type of damage and signed to joints, panel points, beam lines, han- measure the offset or deflection. gers, and floor connections to make it possible (4) Hangers, Pins, and Expansion Devices. to identify each part of the structure. Refer to Hangers, pins, and expansion devices may be Chapter III for an explanation and examples of inoperative, worn, damaged, or deteriorated. coding. A sketch showing the identification sys- Pins may be scored. Any of these components tem should be a part of the inspection form. may corrode, causing them to lock or freeze. Before, or during, the inspection the identifying This condition can be detected by noting that marks should be crayoned or painted on the hangers or expansion rockers are inclined or bridge in order to keep track of the inspector's rotated in a direction opposite to what would be location and to guard against overlooking any expected for the temperature at the time of portion of the structure. inspection, e.g., a rocker leaning away from the d. Superstructure Inspection. Inspect the var- fixed end of the span in cold weather. Heavy ious parts of the superstructure as outlined in rust accumulation on pin joints and on roller Chapter V. Look for : nests also indicates a locked joint, (1) Corrosion (5) Rivets and Bolts. Tightness of a rivet (2) Cracking may be tested by placing the thumb beside the rivet and striking the rivet sharply on the other (3) Splitting side with a hammer. If the rivet is loose, its (4) Connection slippage movement will be felt by the thumb. On hori- (5) Deformation due to overload zontal surfaces a washe. or nut may be used (6) Damage caused, when struck by vehi- instead of the thumb. Tightness of bolts may be cles or vessels tested with a torque wrench (fig. 4-2). Where the main load of the bridge is carried by g. Concrete Member Inspection. Most types a single member, or element whose failure of deterioration will be readily observed. Much would result in the collapse of the structure, the of the deterioration will occur on decks or in member should be inspected very thoroughly areas exposed to roadway drainage. for cracks and flaws either by visual inspection (1) Cracking. Cracking will usually be or by a non-destructive technique, such as ultra- large enough to be seen with the naked eye. sonics or radiography. The pins and the han- Rust or efflorescence stains will often appear at gers on the suspended span of a two-girder can- the cracks, and should be reported.. Large tilever bridge, or the pins in a pin-connected cracks in the main members, especially in pre- truss, are typical examples of such members. stressed concrete members, should be carefully e. Pre-inspection Cleaning. It will often be recorded. necessary to remove dust, debris, rust, paint (2) Spalling. Tap the deck with a hammer scale, or animal wastes before inspecting a over a large area outside the apparent spall to bridge member. Scrapers, wire brushes, air locate hollow zones or areas of incipient spall- jets, or shot blasting are very useful for this ing. When larze areas of spalling are expected, purpose. A clean surface is particularly impor- a heavy chain attached to a truck may be tant when electronic devices are used for dragged across the deck. inspection of steel or concrete. h. Timber Structures. f. Steel Member Inspection. (1) Weathering and Wear. Note severity (1) Rust. Note extent and severity of rust. of weathering and wear. Use calipers to measure thickness of metal (2) Decay and Insect Attack. Damage due when loss of section has occurred. Metal thick- to decay or insect attack is often not visible ness can also be measured ultrasonically. because it is confined to the interior of the tim- (2) Cracks. Note length, size, and location ber members. Hidden deterioration can be de- of cracks. Classify cracks as fine, medium, or tected by use of an increment borer or by stick- open. ing an ice pick into the wood. Insects may also (3) Damaged or Bent Members. Members leave small piles of sawdust as evidence of their may be damaged or bent because of collisions or presence.

4-4 (3) Collision or Overloading. Large cracks, rusting and crackingsince many of these splits, or crushed areas will be readily visible if bridges may have been in use for many years timber members have been exposed to collision without benefit of adequate maintenance. So- damage or overloads. phisticated inspection techniques, such as ultra- (4) Section Loss. Record carefully the lo- sonics,are recommended for inspectionof cation and size of any defect and estimate the wrought iron bridges. section loss. The section loss (width of defect j. Secondary Members. Secondary members times depth of defect) should be reported as a include cross frames, bracing, and other mem- percentage of the original cross sectional area. bers whose functions are to stiffen the bridge (5) Fire Damage. Note signs of fire dam- and to distribute the loads to the main mem- age, particularly on bridges located in isolated bers. These should be inspected in the same way areas. as the main supporting members. (6) Nicks and Cuts. Examine areas where k. Decks. the protective treatment of timber has been bro- (1) Take a series of profile elevations along ken by nicks, cuts, or drilling. the centerline and gutter lines of all long-span bridges. This information should be plotted and i.Wrought Iron Structures. Wrought iron compared with the original profile grade lines structures should be carefully examined for for that structure.

t; rt,Pi b 41/f 1,,

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*ck m Courtesy of Bethlehem Steel Co. Figure 4-2.Torque wrench ,being used for checking bolts.

4-5 (2) Examine the decks for various defects, (1) Excessivevertical displacement be- noting size, type, extent, and location of each tween approach pavement and the bridge deck. deficiency. Use the centerline and shoulderline (2) Improper joint width. as references for describing location. (3) Clogged joints. 1. Expansion Joints. Measure and record the (4) Cracks and potholes. width of the opening of all expansion joints. b. Inspect signing for : Examine the condition of the expansion joints. Record the temperature and weather at the (1) Presence ofnecessaryclearance, time of inspection. weight limit, and other warning signs. (2) Condition of signs. m. Bearing Devices. c. Lighting. Inspect adequacy of : (1) Measure rocker tilts with respect to a fixed reference line. (1) Highway lighting. (2) Measure location of sliding bearings to (2) Navigation lights. the nearest 1/8 inch with respect to a fixed ref- (3) Aerial obstruction lights. erence point. (4) Condition of light standards. (3) Measure deformation and bulging of elastomeric pads. 4-2.5 Movable Bridges. (4) Record the temperature and weather Movable bridgesshould beobserved while at the time of inspection. closed, open, and operating. Observe and record the following: 4-2.4 Approaches, Lighting, and Signing. a. The spans' overall behavior. a. Check approaches for b. Safety gates and warning signals.

Figure 4-3.Inspection catwalk and handrails under girder bridge. Note access ladder on backwall. 4-6 c. The mechanical and electrical aspects. camera for underwater photography is very d. Navigation and aerial obstruction lights. helpful ; strong lights to illuminate the piles are essential. e. Shear locks, wedges, and stops. f. Check scour development, if necessary. f. Any valid complaints or information the operators may offer. 4-2.7 Accessibility. 4-2.6 Underwater Inspection. a. General. Special equipment will be needed for some bridges to make all members accessi- Underwater inspection of piles and substruc- ble. Most high-level bridges have been provided tures will be performed by an experienced diver with inspection catwalks (fig. 4-3) or travelers who will accomplish the following tasks: under the bridge, or with hand rails along the a. Note serious rusting of steel piles. suspension cables. Some of the newer steel girder bridges have hand rails welded to the webs b. Note deterioration of splitting of concrete and stiffeners to make inspection tasks less haz- (including prestressed) piles. ardous (fig. 4-4). c. Note insect infestation and deterioration b. Piles and Piers. Submerged piles and piers of timber piles. can be inspected only by a diver. d. Measure the amount of pile loss and esti- c. Underside of Bridge. Ladders canbe used mate remaining section. for inspecting the underside of a bridge from e. Scrape marine growth off the piles when the ground if the structure is not too necessary for unobstructed vision. A television When the beams cannot be reached from the

- :

s?"

Figure 4-4.Rods welded to ace/ members serve as handgrips to facilitate

4-7 ground, ladders or planking between beams and f. Helicopters. Helicopters may be used to catwalks can be used. Scaffolding, platforms photograph the tops and sides of high bridges. suspended from the parapet on each side of the Development of corrosion or deterioration can structure, or hydraulically operated platform be readily seen by comparing aerial photos that trucks can also be used. have been taken over a period of several years.

d. Superstructure. On high trusses, suspen- 4-2.8 Summary. sion bridges, and arches, it is usually necessary to climb the superstructure. In doing so, the The most important aspects of a good inspec- inspector should make every effort to minimize tion are : his risk. He should look for vantage points from a. Proper planning of the inspection to ensure which a relatively large area, or a large number that attention is given to each bridge compo- of members or details, can be seen clearly with- nent in accordance with '.1:s importance. out requiring him to change his position. b. Preparation according to the inspection e. Platforms. Hydraulically operated plat- plan. forms can be used on through trusses, although c. Careful and attentive observation. they have the disadvantage of occupying the d. Thorough and complete recording of every shoulder of the roadway. item inspected.

4-8 CHAPTER V

BRIDGE COMPONENT INSPECTION GUIDANCE

5-0.0 Introduction. crete deteriorates because of scaling, spalling, At this point, the bridge inspector sl:ould be and cracking; while timber is subject to weath- familiar with the terminology and elementary ering, decay, fungus, and insect attacks. theory of bridge construction. He should be fa- In addition to construction materials, another miliar with the tools, devices, and specialized very important material involved in bridge con- equipment used during the bridge inspections, struction is the soil on which the bridge founda- and with all of the safety precautions that must tion rests. When the soil or the bridge founda- be taken in the course of his inspection. The tion moves, serious structural difficulties can de- bridge inspector should have an understanding velop. These movements fall into several catego- of the planning, organization, and preparation ries:lateralmovement,vertical movement that is necessary to undertake and complete a (s...tement), pile settlement, and rotational or meaningful bridge inspection. tipping movements. The causes of these move- However, to be fully qualified to examine ments slope slides, bearing failures, consoli- bridges, he needs to know what defects and de- dation of soil, seepage, frost action, ice, thermal ficiencies to look for. He needs to know what forces, including pavement thrust, and drag situations and conditions represent actual or forces on piles. potential injury to the bridge or impair public A common cause of bridge failure is the phys- safety. Chapter V instructs,informs, and ical failure of a member due to overloads or guides the bridge inspector so as to enable him collisions. Substructure and superstructure ele-_ to recognize the various kinds of bridge de- ments should be closely inspected for the types terioration, to pinpoint their location, and to of distress discussed in the sections dealing categorize and describe their severity. with the various materials. The discussion will be concerned primarily Waterways and navigation fenders should be with the commonly encountered bridge deterio- inspected to determine their condition with re- ration problems. The inspection of specialized gard to maintenance. Bridge approaches, drain- bridge types and components such as those age, lighting, signing, and utilities should be found on Movable and suspension bridges will checked, and any condition considered to be require theassistanceof speciallytrained below acceptable standards should be noted and bridge inspection personnel. Therefore, Section reported. 5-32, Movable Bridget:, and Section 5-34, Sus- It will be necessary for the inspector to exer- pension Spans, should not be construed as a cise his oWn judgment in performing his tasks. complete treatment of the subjects. Bridge--However, he should not hesitate to consult his inspectionsrequiring underwater investga- superiors or inspection specialists whenever a tions should be performed with the guidance problem is beyond his experience or capabili- and assistance of individuals experienced in ties. It is most important that the inspector re- this specialty. alize the necessity for reporting the severity, The type of materials used in the construc- location, and extent of the deterioration. De- tion c):f the bridge will establish initially the scriptions of deterioration should be factual, particular kinds of deterioration the inspector complete, and documented by a photograph or a will be looking for during his inspection. For sketch whenever practical. The professional en- example, rust is the great enemy of steel; con- gineer who heads the inspection team should

5-1 encourage frank and open discussions among all d. Fire Resistance. High quality concrete members of the team to ensui.e full exchange of highly resistant to the effects of fire. However, information concerning the inspection task. intense heat will damage concrete. Figure 5-1 illustrates the type of damage that can be caused by fire. Section 1.CONCRETE e. Elasticity. Concrete under ordinary loads is elastic, i.e., stress is proportional to strain. 5-1.1 General. Under sustained loads the elasticity of concrete Concrete is essentially a compressive material. issignificantly lowered due tocreep. This While it has adequate strength for most struc- makes concrete less likely to crack. tural uses, it is best suited for relatively mas- f. Durability. The durability of concrete is sive members that transmit compressive loads affected by climate and exposure. In general, as directly to the fqunding material. Although con_ - the water-cement ratio is increased, the durabil- crete has low tensile strength, reinforcing it ity will decrease correspondingly. Properly pro- with steel bars produces a material that is suit- portioned, mixed, and placed concrete is very able for the construction of flexural members, durable. such as deck slabs, bridge girders, etc.Pre- stressed concrete is produced by a techniTik g. Anisotropy. Concrete itself is generally iso- which applies compression to concrete by means tropic, but once reinforced with steel bars or of highly stressed strands and bars of high prestressed with steel wires, it becomes aniso- strength steel wire., This compressive stress is tropic, i.e., its strength varies depending on the sufficient to offset the tensile stress caused by direction in which it is loaded. the applied loads. Prestressing has greatly increased the maximum span length of concrete 5-1.3 Factors Causing Deterioration. bridges. a. Freezing and Thawing. Porous concrete absorbs water, which upon freezing creates 5-1.2 Physical and Mechanical Properties of high expansive pressures. These pressures ulti- Concrete. mately produce cracking, Scaling, and spalling. The principal properties of concrete that are of interest and concern to the bridge inspector are discussed below. While concrete possesses several other properties such as thermal conductivity, volume change, mass, and energy absorption, these are not directly related to .the problems of bridge maintenance and, therefore, are not discussed. a. Strength. Compressive strength is high, but shear and tensile strengths are much lower, being about 12% and 10%, respectively, of the compressive strength. b. Porosity.Concrete is inherently porous and permeable since the cement paste never completely fills the spaces between the aggregate particles. This permits absorption of water by capillary action and the passage of water under pressure.

c. Extensibility. Concrete is said to be exten- Courtesy of Michigan State Highway Dept. sible, i.e., undergoes large extensions without Figure 5-4.Concrete damaged by intense heat. Note cracking. However, this presupposes a high the cracking and spalling of the reinforced concrete quality concrete and freedom from restraint. pier cap.

5-2 b. Salt Action. The use of salt or other deic- 1. Rusted Reinforcing Steel. The increase in ing agents contributes to weathering through volume due to rust exerts expansive pressures recrystallization, in a fashion similar to that on concrete. incurred in freezing and thawing. Salt also in- Creases water retentionor may chemically 5-1.4 What to Look for During Inspection. attack the concrete if certain compounds are a. Scaling. The gradual and continuing loss of present. surface mortar and aggregate over an c. Differential Thermal Strains. Large tem- should be classified as follows: perature variations, which set up severe differential strains between the surface and the interior of a concrete mass, are an occasional cause ofconcretedeterioration.Aggregates with lower coefficients of thermal expansion than the cement paste may alsoset up high tensile stresses. .7 d. Unsound Aggregates. Being structurally weak and/or readily cleavable, these materials are vulnerable to the weathering effects of moisture and cold. e. Reactive Aggregates and High Alkali Con- crete. Cracking and a weakened concrete structure result from these combinations, especially where the concrete is exposed to the elements. f. Sulfate Compounds in Soil and Water. So- dium, magnesium, and calcium sulfates have a 17. deleterious effect upon compounds in the cement paste and cause rapid deterioration of the con- ..b crete. , Courtesy of Portland Cement Association. g. Leaching. Water seeping through cracks Figure 5-2Light scale. Scale depth isless than 14". and voids in the hardened concrete leaches or dissolves the calcium hydroxide and other material compounds. The resultant of such action is either efflorescence or incrustation at the surface of the cracks. h. Chemical Attack. A number of chemicals attack concrete. However, highway structures are usually subjected to only those chemicals present in deicing agents. i.Wear or Abrasion. Traffic abrasion and impact cause wearing of bridge decks ;while curbs, parapets, and piers are da'aiaged by the scraping action of such vehicles as snow plows and sweepers. Deck wear also appears as cracking and ravelling at joint edges. j. Foundation, Movements. These movement, will cause serious cracking in structures. (See Section 5-7, for further discussion.)

k. Shrinkage and Flexure Forces. Both of Courtesy of Portland Cement Association. these kinds of forces set up tensile stresses that Figure 5-3.Medium scale. Scale depth is between result in cracks. 14" and 1/2".

5-3 (1) Light Scale. Loss of surface mortar up to 14" deep, with surface exposure of coarse aggregates (fig. 5-2). (2) Medium Scale. Loss of surface mortar from 14" to 1/2" deep, with some added mortar loss between the coarse aggregates (fig. 5-3). (3) Heavy Scale. Loss of surface mortar surrounding aggregate particles of 1/2" to 1" deep. Aggregates are clearly exposed and stand out from the concrete (fig. 5-4). (4) Severe Scale. Loss of coarse aggregate particles as well as surface mortar and the mortar surrounding the aggregates. Depth of the loss exceeds 1" (fig. 5-5). NOTE : The inspector should describe the character of the scaling, the approximate area involved, and the location of the scaling on the bridge. b. Cracking. A crack is a linear fracture in the concrete. Cracks may extend partially or completely through the concrete member. While a great many cracks may be in the deck, they - will also occur in abutments and wing walls and Courtesy of Portland Cement Association. may appear in areas adjacent to vertical expan- Figure 5-4.Heavy scale. Note depth is between. 1 /2" sion joints. Cracks often appear in pier caps, and 1". Note virtually complete exposure of course parapets, T-beams, box girders, and all other aggregate. concrete elements. When reporting cracks, describe their type, size, length, direction, and lo- We' cation. Compare the results of the current inspection \Pith those of previous inspections to determine whether crack formation is continuing or whether it has been halted. Since cracks are one of the most reliable indications of fu-

Courtesy of Portland Cement Association. Figure 5-5.Severe scale. Scale depth is greater than 1". Note dislodgement of course aggregate and expo- Courtesy of Portland Cement Association. sure of reinforcing bars. Figure 5-6.Transverse cracking. 5-4 tare trouble, it is important to determine their (1) Transverse Cracks. These are fairly cause and extent. Cracks are categorized as fol- straight cracks that are roughly perpendicular lows: to the center line of the roadway (fig. 5-6). Transverse cracks vary in width, length, and in ti spacing. They frequently occur over the main slab reinforcement on stringer bridges. Cracks may extend completely through the slab. These

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Courtesy of Portland Cement Association. --, - Figure 5-7.Longitudinal cracking. Courtesy of Portland Cement Association. Figure 5-9.Pattern. or 'map cracking.

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Courtesy of Portland Cement Association. Courtesy of Portland Cement Association. Figure 5-8.Diagonal cracking. Figure 5-10.D-cracking.

5-5 size, and appear similar to that of sun-cracking seen on dried flats. They vary in width from barely lisible, fine cracks to well-defined openings (fig. 5-9). They are found in both slabs and walls. (7) D-cracks. These are usually defined by dark colored deposits, generally near joints and edges (fig. 5-10). They may widen gradually and eventually produce failure. Vertical cracks near vertical expansion joints in abutments and walls can also be classified as D-cracks. This type of cracking may be indicative of alkali reactive concrete. (8) Random Cracks. These are meandering irregular cracks appearing on the surface of slabs. They have no particular form and do not Courtesy of Portland Cement Association. logically fall into any of the classifications de- Figure 5-11.Random cracking. scribed above (fig. 5-11). c. Spoiling. Spalling is a roughly circular or same cracks may extend through curbs, side- oval depression in the concrete. It is caused by walks, and parapets. On skewed bridges where the separation and removal of a portion of the the transverse deck steel is not placed at right surface concrete revealing a fracture roughly angles to the roadway center line, this type of parallel, or slightly inclined, to the surface. crack may appear parallel to the deck steel. On Usually, a portion of the depression rim is per- continuous structures, pronounced transverse pendicular to the surface. Often reinforcing cracking may be noted in or near the negative steel is exposed as shown in fig. 5-12. Spalling moment zones over the piers. Pier caps are also may be classified ae follows : subject to transverse cracking. (2) Horizontal Cracking. Cracking of this kind will occur in walls, abutments, pier stems, and columns. They are similar in nature to transverse cracks, and may be listed as such. (3) Longitudinal Cracks. These are fairly straight cracks (in slabs) running parallel to the center line of the roadway. They are of variable widths, lengths, and spacings. These cracks may extend partially or completely through the deck (fig. 5-7). (4)Verticat Cracks. Vertical cracks in ....,.. . walls, abutments, pier sterns, and caps are simi- wlyO. "-'''.. ..,NO.' ...'-','ZI'''..'''' , lar to longitudinal cracking in slabs, and should .11 -er ...4,..-..--,.?.; be described as such. (5) Diagonal Cracks. These cracks appear roughly parallel in slabs skewed to the center line of the bridge. They are usually shallow and .... are of varying lengths, widths, and spacings (fig. 5-8). When found in the vertical faces of beams or pier caps they may be deeper than -- 4 usual, and thus pose a more serious problem. 1)1 (6) Pattern or Map Cracking. These inter- Courtesy of Portland Cement Association. connected cracks form networks of varying Figure 5-12.Small surface spall. 5-6 (1) Small. Not more than 1" deep or approximately 6" in diameter (fig. 5-12). (2) Large. More than 1" deep and greater than 6" in diameter (figs. 5-13 and 5-14). (3)Hollow Area. An area of concrete which gives off a hollow sound when struck with a hammer or steel bar, indicating the ex- istence of a fracture plane below the surface.

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. Courtesy of Portland Cement Association. Figure 5-15.Joint spall.

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Courtesy of Portland Cement Association. Figure 5-13.Large surface spall.

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Courtesy of Portland Cement Association. Courtesy of Portland Cement Association. Figure 5-14.Surface spall exposing reinforcing steel. Figure 5-16.Popout.

5-7 b. Ductility. Both the low carbon and low alloy steels normally used in bridge construction are quite ductile. Brittleness mayoccur because of heat treatment, welding, or through metal fatigue. c, Durability. Steel, when protected properly, is extremely durable. d. Fire Resistance. Steel is subject to a loss of strength when exposed to high temperatures such as those resulting from fire (fig. 5-18). e. Corrosion. Unprotected carbon steel cor- rodes (rusts) readily, However, itcan readily be protected. f. Weldability, Although steel is weldable, it Courtesy of Portland Cement Association. is necessary to determine the chemistry of the Figure 5-17.Mudballs. steel and to select a suitable welding procedure before starting welding operations d. Joint Spall. This is an elongated depression on a bridge. along an expansion, contraction, or construction g. Others. Steel is elastic and conducts heat joint (fig. 5-15). and electricity. e. Pop-Outs. These are conical fragments that break out of the surface of the concrete leaving 5-2.3 Factors Causing Deterioration. small holes. Generally, a shattered aggregate particle will be found at the bottom of the hole, a. Air and Moisture. Air and moisture cause with a part of the fragment still adhering to the rusting of steel, especially in a marine climate. small end of the pop-out cone (fig. 5-16). b. Industrial Fumes. Industrial fumes in the atmosphere, f. Mudballs. These are small holes that are particularlyhydrogensulfide, left in the surface by the dissolution of clay cause deterioration of steel. balls or soft shale particles (fig. 5-17). c. Deicing Agents. While all deicing agents attack steel, salt is the most commonlyencoun- In recording the last four defects, describe the tered chemical on bridges. type, depth, dimension, and location together with a sketch, drawing, or photograph,as ap- d. Seawater and Mud. Unprotected steel propriate. members, such as piles immersed in water and embedded in mud, undergo serious deterioration and loss of section. Section 2. STEEL e.Thermal Strains or Overloads. Where 5-2.1 General. movement is restrained, or where membersare overstressed, the steel may yield, buckle,or Steel, a highly reliable and versatile construc- crack (or rivets and bolts may shear). tion material, is available inmany formswire, cable, plate, and shaped barsor beams. Many of f. Fatigue and Stress Concentrations. Cracks the nation's larger bridgesare constructed pri- may develop because of fatigue or poor details marily of steel. which produce high stress concentrations.Ex- amples of such details are : re-entrantcorners, 5-2.2 Physical and Mechanical Properties of abrupt and large changes in plate widthsand/ Steel. or thicknesses, a concentration of heavy welds, a. Strength. Steel possesses tremendous com- or an insufficient bearing area for a support. pressive and tensile strength and is highlyre- g. Fire. Extreme heat will cause serious de- sistant to shear forces. Thin steel sections, how- formations of steel members. ever, are vulnerable to compressive buckling: h. Collisions. Trucks, over-height loads, de- 5-8 woloWNO011igiffiairtF4

Courtesy of Michigan State Highway Dept. Figure 5-18.Steel beams subjected to intense heat. Note deflection of members. railed railroad cars, etc., may strike steel beams or columns, damaging the bridge. i. Animal Wastes. These may cause rusting, and can be considered as a special type of direct chemical attack. j. Welds. Where the flux is not neutralized, some rusting may occur. Welds may crack because of poor welding techniques or poor weldability of the steel. k. Galvanic Action. Other metals that are in contact with steel may cause corrosion similar to rust.

5-2.4 What to Look for During Inspections.

a. Rust. Rusted steel varies in color from Courtesy of District of Columbia Highway Dept. dark red to dark brown. Initially, rust is fine Figure 5-19.Rust on floor stringer. Note that web is grained, but as it progresses, it becomes flaky completely rusted through.

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14 14'ai?. jit l'!1 4 Figure 5-20.Steel bearing pile deterioration. Severe rusting occurred between concrete jacket and mud line. Note loss of sert^..m. or scaly in character. Eventually, rust causes a b. Cracks. Cracks in the steel may vary from pitting of the member. The inspector should hairline thickness to sufficient width to transmit note the location, characteristics, and the extent light through the member. Any type of crack is of the rusted areas. The depth of heavy pitting obviously serious, and should be reported at should be measured and the size of any perfora- once. Record the location and length of all tion caused by rusting should be recorded. Rust cracks and indicate whether the cracks are open may be classified as follows : or closed. (1) Light. A light, loose rust formation c. Buckles and Kinks. These conditions de- pitting the paint surface. velop mostly because of damage arising from (2) Moderate. A looser rust formation thermal strain, overload, or added load condi- with scales or flakes forming. Definite areas of tions. The latter condition is caused by the fail- rust are discernible. ure or the yielding of adjacent members or components. Collision damage may also cause buck- (3) Severe. A heavy, stratified rust or rust les, kinks and cuts. Look for cracks radiating scale with pitting of the metal surface. This from cuts or notches. Note the members dam- rust condition eventually culminates in the per- aged, the type, location, and extent of the dam- foration of the steel section itself (figs. 5-19 age, and measure the amount of deformation, if and 5-20). possible.

5-10 d. Stress Concentrations. Observe the paint 5-3.2 Factors Causing Deterioration. around the connections at joints for fine cracks Deterioration can be prevented or greatly re- which are indications of large strains due to duced by proper preservative treatment. How- stress concentrations. Be alert for sheared or ever, in existing structures, it is often difficult deformed bolts and rivets. to tell what preservative treatment has been e. Structural Steel. Inspect structural steel used. partially incased in substructure concrete at.the a. Fungi. Fungi usually require some mois- face of exposure for deterioration and for ture. As a rule, fungus decay can only be movement. avoided by excellent preservative treatment. f. Galvanic Corrosion. This condition will ap- b. Vermin. These tunnel in and hollow out the pear essentially similar to rust. insides of timber members for food and/or shelter.

Section 3. TIMBER (1) Termites (2) Powder-post beetlesandcarpenter 5-3.1 Physical and Mechanical Properties of ants Timber. (3) Marine borers a. Strength. Timber, while noi as strong as c. Weathering, Warping, etc. This is normally steel approximates ordinary concrete in com- caused by repeated dimensional changes in the pressive strength. Rated strongest in flexural woodusually due to repeated wetting. strength, timber has an allowable compressive d. Chemicals. These act in three different strength (parallel to grain) of about 75% of ways: a swelling and resultant weakening of the flexural value. Perpendicular to the grain, the wood, a hydrolysis of the cellulose by acids, compressive strength is only 20% of the flex- or a delignification by alkalis. Animal wastes ural strength. I-Turizontal shear.is limited to are also a problem. 10% of the flexu..al strength. e. Fire. Timber is particularly vulnerable to b. porosity. Being a cellular, organic mate- fire. rial, timber is quite porous. f. Abrasion or Mechanical Wear. Abrasion is c. Anisotropy. As may be deduced from the most serious when combined with decay which differences in allowable compressive strengths, softens or weakens the wood. On bridges, decks wood is anisotropic, i.e., it has different strength are especially vulnerable. properties depending upon the manner and g. Collisions and Overleadings. Damage will direction of loading. be evident in the form of shattered or injured timbers, sagging or buckled members, or tim- d. Impact Resistance. Since timber is able to bers with large longitudinal cracks. Give loca- withstand a greatly increased load momentar- tion and extent of damage and determine ily, neither impact nor fatigue are serious prob- whethe.r immediate repairs are necessary. lems with timber. e. Durability. Under certain conditions, and 5-3.3 What to Look for During Inspection. when properly treated or protected, timber is quite durable. However, timber is not a particu- a. Fungus decay. larly durable material under all conditions. It (1) Mild. Mild fungus decay appears as a should be noted that some preservative treat- stain or discoloration. It is hard to detect and ments reduce the strength of timber. even harder to distinguish between decay fungi and staining fungi. f. Fire Resistance. Timber is very vulnerable (2) Advanced. Wood darkens further and to damage by fire. shows signs of definite disintegration, with the g. Timber is also elastic, low in thermal and surface becoming punky, soft and spongy, electrical conductivity and subject to volume stringy, or crumbly, depending upon the type of changes. decay or fungus (fig. 5-21). It is similar to dry

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Figure 5-22.Teredo damage in top-gradegreenheart. 5-12 I

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Figure 5-23.Sections of treated timber piling. Note that damage starts at bolt holes. Figure 5-24.Limnoria, underside view.

Figure 5-25.Limnoria damage in tidal zone.

5-13 from the earth to the wood and on the sides of r masonry substructures are theonly visible signs of infestation. If the timber members exhibit signs of excessive sagging or crushing, check for termite damage with an ice pick or an increment borer. (2) Powder-Post Beetles. The outer surface is pocked with small hales. Often a pow- dery dust is dislodged f,om the holes. The inside may be come lef excavated. (3) Carpenter Ants. Accumulation of sawdust on the ground at the base of the timber is an indicator. The large, black ants maybe seen in the vicinity of the infested wood. (4) Marine Borers. The inroads of marine borers will usually be most severe in the area tie between high and low water since they are water-borne, although damage may extend to the 11,r4: ..:1,:::;tt; mud line. Where piles are protected by concrete or metal shielding, the shieldsshould be inspected carefully for cracks or holes that would permit entrance of the borers. Unplugged bolt Figure 5-26.Limnoria attack in treated timber placed holes also permit entrance of these pests. (Figs. in tidal zone. Damage starts at bolt holes and cuts. The discs on the surface of the timber are -marine 5-23 and 5-26.) In such cases, there are often growth. no outside evidences of. borerattack." The inspector should list the locations and extent of damage and indicate whether it is feasible to rot of door posts and outside porches. Fruiting exterminate the infestation and strengthen the bodies of fungi, similar to those seen on old member or if immediate replacement is neces- stumps, may develop. The inspector should note sary. the location, depth of penetration, and size of (a) Mollusk Borers (Shipworms). The the areas of decay. Where decay occurs at a shipworm is one of the most serious enemies of joint orsplice,indicatetheeffecton the marine timber installations. The most common strength of the connection. Use a knife, icepick, species of shipworm is the teredo. This ship- or an increment borer to test for decayed wood. worm enters the timber in an earlystage of life Decay is very likely to occur at connections, and remains there for the rest of its life. Tere- splices, support points, or around bolt holes. dos reach a length of 15 inches and a diameter This may be due either to the tendency of such.of 3/8 inch, although some species of shipworm areas to collect and retain moisture, or to bolt grow to a length of 6 feet. The teredomaintains holes or cuts being made in the surface after a small opening in the surface ofthe wood to the preservative treatment has been applied. obtain nourishment from the sea water. Figures Unless these surfaces are subsequently pro- 5-22 and 5-23 show shipworm damage. tected, decay is very likely. Any holes, cuts, (b) Crustacean Borers. The most com- scrapes or other breaks in the timber surface monly encountered crustacean borer is the lim- which would break the protective layers of the noria or wood louse (fig. 5-24). It bores into the preservative treatment, and allow access to un- surface of the wood to a shallow depth. Wave treated wood should be noted. action or floating debris breaks down the thin b. Vermin. shell of timber outside the borers' burrows, (1) Ter.mites. All damage is inside the sur- causing the limnoria to burrow deeper. The con- faces of the wood; hence, it is not visible. White tinuous burrowing results in a progressive dete- mud shelter tubes or runways extending up rioration of the timber pile cross section which

5 -14 Figure 5-27.Limnoria attack in tidal zone. Attack beganat cut off ends of braaing and progressed through+ bolt holes into piling.

will be most noticeable by the hour glass shape Usually this type of damage will have been re- developed between the tide levels. Limnoria ported prior to the inspection. damage is illustrated in figures 5-25, 5-26, and f. Mechanical Wear. Wear due to abrasion is 5-27. readily recognized by the gradual loss of section c. Weathering. at the points of wear. The inspector should report the location, the general area subject to (1) Slight. Surfaces of wood are rough and wear, and the loss in thickness. He should also corrugated, and the members may even warp indicate whether immediate remedial action is (fig, 5-28). necessary. (2) Advanced. Large cracks extend deeply or completely through the wood. Wood is crum- g. Collision. Shattered or injured timbers are bly and obviously deteriorated (similar to tips indications of collision. Give location and extent of roof shingles at the eaves). of danw.ge and determine whether immediate measures are needed. d. Chemical Attack. This will resemble decay. h. 'Unplugged holes, such as those left by test e, Fire. Fire damage is easily recognized. borings, nails, bolts, and the like.

5-15 Figure 5--28.Weathering and wear of untreated timber deck.

Section 4. WROUGHT ANA CAST IRON (1) Strength. Wrought iron has an ultimate tensile strength of about 50,000 psi. How- ever, the rolling process and presence of the 5-4.1 General. slag inclusions make wrought iron anisotropic ; a. Wrought iron is a metal in which slag inclu- wrought iron has a tensile strength across the sions are rolled between the microscopic grains grain of about 75% of its longitudinal strength. of iron. This results in a fibrous material with While this characteris4-c has been largely elimi- properties quite similar to steel, although ten- nated in the wrought iron made today, wrought sile strength is lower than in steel. iron in the old bridges will be anisotropic. b. Cast iron is iron in which carbon has been (2) Elasticity. Wrought iron has an elastic dissolved. Other elements which affect the prop- modulus of 24,000,000 psi-29,000,000 psi, This erties of cast iron are silicon and manganese. In is nearly as high as steel. general, a wide range of properties are obtained (3) Ductility. Wrought iron is generally depen-g upon the alloying elements used. ductile, although its ductility depends, to a large extent, upon the method of manufacture. 5-4.2 Physical and Mechanical Properties. (4)Toughness and Impact Resistance. a. Wrought Iron. Wrought iron is to. ,LYesistant to impact. 5-16 (5) Corrosion Resistance. The fibrous na- 5-5.2 Physical and Mechanical Properties. ture of Nrought iron produces a tight rust a. Strength. Stone has more than adequate which is less likely to progress to flaking and strength for most loads. scaling tnan is rust on carbon steel. (6) Weldability. Wrought iron is welded b. Porosity. While all stone is porous, sand- with no great difficulty. However, care should stone and some limestones are much more so be exercised when planning to weld the metal than granite. of an existing bridge. c. Absorption.. Most stone is absorptive, especially limestone. b. Cast iron (1) Strength. The tensile strength znf cast d. 17;,ermal Expansions. Stone expands and iron varies from 20,000 psi to 60,000 psi, de- contracts with temperature variations. pending upon its composition. In dealing with e. Thermal Conductivity. Stone is generally a the iron in old bridges, it must be assumed that poor conductor of heat. the cast iron will be near the lower end of the f.Durability. Stone is more durable than scale. The compressive strength of cast iron is most materials, although there is a wide range high, from (30,000 psi up. For this reason, cast indurability between differentvarieties of iron was used for compression members in the stone. early iron bridges, while wrought iron was used for tension members. g.Fire,,esistance. While not flammable, stone; can be damaged by fir: (2) Elasticity. Cast iron has an elastic modulus of 13,000,000 psi to 30,000,000 psi. 5-5.3 Factors Causing Deterioration. (3) Brittleness. Cast iron is brittle. (4) impact Resistance. Cast iron possesses a. Chemicals. Gases and solids dissolved in good impact resistance properties. water often attack rocks chemically. Some of these solutions can dissolve cementing com- (5)Corrosion Resistance. Cast iron,in pounds between the rocks. Oxidation and hy- general, is more corrosion resistant than the dration of some compounds found in rock will other ferrous metals. also cause damage. (6) Weldability. Due to its high carbon content, cast iron is not easily welded. b. Seasonal Expansion and Contraction. Re- peated volume changes produced by seasonal ex- 5-4.3 What to Look for During Inspection. pansion and contraction will cause tiny seams to develop, thereby weakening the rock. a. In general, a wrought iron structure will be inspected similarly to a steel structure. c. Frc t and Freezing. Water freezing in the seams and pores of rocks can split or spall rock. b. Cast iron should also be inspected similarly d. Abrasion. Abrasions are due mostly to to steel. It should be noted that cast iron is sub- wind or waterborne particles. ject to defects such as checks (cracking due to tensile cooling stresses) and blowholes. Thelat- e. Plant Growth. Lichens and ivy will attack ter has a serious effect on both the strength and s,,one surfaces chemically in attaching them- toughness of the cast iron. selves to the stone. Roots and stems growing in crevices or joints exert a wedging force. Section 5.STONE MASONRY f.MarineBorers.Rock-boring mollusks attack rock by means of chemical secretions. 5-5.1 General. Stone masonry is little used today, except as 5-5.4 What to Look for During Inspection. facing or ornamentation. However, some old stone structures are still in use. The types of a. Weathering. The hard surface degenerates stones commonly used in bridges are granite, into small granules, giving stones a smooth, limestone,andsandstone,althoughmany rounded look. smaller bridges or culverts were built of stones b. Spalling. Small pieces of rock break out or locally available. chip away.

5-17 c.Splitting. Seams or cracks open up in the soil or by a shear failur.e. Slope slides and rocks, eventually breaking them into, smaller bearing failures are good examples of shear pieces. failures. Where loads are not large enough to cause shear failure, settlements may still occur as a result of volume change. The length of time Section6. ALUMINUM and magnitude of the settlements depend upon the composition of the soil. Granular solids, 5-6.1 General. such as sand, will usually undergo a relatively While aluminum has been widely used for signs, small volume change ih a short period of time. light standards, railings, and sign bridges, it is However, cohesive soils, such as clay, can un- seldom used as the principal material in the dergo large deformations, or volume changes, construction of vehicular bridges. While most which may continue for years. This latter proc- properties of aluminum are similar to those of ess, called consolidation, is usually confined to steel, the following differences exist : clays and clayey silts. Substructhres that are a. Lightness. Aluminum weighs about one- supported directly by a cohesive soil may con- third ( V) as much as steel. 'thine to settle for a long period of time. Consoli- dation usually prochices vertical settlement. b. Strength. Aluminum, while not as strong as steel, will be made comparable to steel in

strength when alloyed. 5-7.2 Types of Movements. . c. Corrosion Resistance. Aluminum is highly For convenience, foundation movements may resistant to atmospheric curosion. also be classified, scrnewhat arbitrarily, into the d. Workability. Aluminum iseasily fabri- following: cated, however, welding requires special proce- a. Lateral Movements. Earth-retaining struc- dures. tures, such as abutments and retaining walls, e. Durability. Aluminum is durable. are susceptible to lateral movements, although piers sometimes also undergo such displace- 5-6.2 What to Look for During Inspection. ments. a. Cracking. Aluminum may be subject to b.Vertical Movements (Settlements). Any some fatigue cracking, Aluminum members type of substructure not founded on solid rock should be examined in areas near the bases of may be subject to settlement (fig. 5-29). cantilever arms and in areas near complex c.Pile Settlements. While pile settlement welded and riveted connections. Weld cracking could be listed under lateral or vertical move- often occurs on sign bridges near those joints ments, it is mentioned separately since there is which are subject to high stresses because of a tendency to consider piles as a panacea for all the misalignment of prefabricated sections. The foundation problems. In addition, some of the combination of high stresses and the vibration causes of failure are peculiar to piled founda- that is caused by winds produces fatigue. tions. b. Pitting. Aluminum will pit slightly, but d. Rotational Movement (Tipping). Rotation this condition rarely becomes serious. movement of substructures can be considered to be the result of unsymmetrical settlements or lateral movements. It will be discussed under Section 7.FOUNDATION MOVEMENTS the movement that is typical of the various substructures. 5-7.1 General. Most foundation movements are caused by movement of the supporting soil. For this rea- 5-7.3 Causes of Foundation Movements. son, it is desirable to give a brief description of The following causes of foundation movements, these movements, although the basic theory in- except as specifically noted, can produce lateral volved is beyond the scope of this Manual.-Soil and/or vertical movements depending on the .deformations are caused b'Y volume changes in characteristics of the loads or substructures.

5-18 Crccks in abutment

WIngwall Rotation

Sand &Gravel

. ---- Soft Clay

. Settlement In cloy _

DenseGravel

Figure 5-29.Differential settlement under an abutment.

a. Slope Failure (Embankment Slides). These structure, or increases in the height of existing are shear failures manifested as lateral move- embankments. ments of hillsides, cut slopes, or embankments. d. Seepage. The flow of water from a point of Footing or embankment loads imposing shear higher head (elevation or pressure) through the stresses greater than the soil shear strength are soil to a point of lower head is seepage (fig. common causes of slides (fig. 5-30). 5-32). Seepage develops a force which acts on b. Bearing Failures. Bearing failures are set- the soil through which the water is passing. tlements or rotations of footings due to a shear Seepage results in lateral movement of retain- failure in the soil beneath (fig. 5-31). When ing walls by: bearing failures, or slope failures, take place on (1) An increase in weight (and lateral an older structure, it usually indicates a change pressure) of the backfill because of full or par- in subsurface conditions. This may endanger tial saturation. the security of nearby structures and founda- (2) A reduction in resistance provided by tions. the soil in front of the structure. c. Consolidation. Serious settlement can re- e. Water Table Variations. Large cyclic vari- sult from ,consolidation action in cohesive soils. ations in the elevation of the water table in Settlement of bridge foundations may be caused loose granular soils may lead to a compaction of by changes in the ground water conditions, the the upper strata. The effectsof non-cyclic placement of additional embankments near the changes in the water table such as consolida-

5-19 Original Slope

Granular Bockfilf

+---- SI Ids Failure Plane

Figure 5-30.Slide failure. tions, slides, and seepage were preyiously dis- h. Ice. Ice can cause lateral movement in two cussed. Changes in the water table may also ways. Where fine grained backfill is used in re- change the characteristics of the soil which sup- taining structures and the water table is above ports the foundation. Changes in soil character- the frost line, the expansion of freezing water istics may, in turn, result in the lateral move- will exert a very large force against a wall. The ment or the, settlement of the foundatidn. piers of river bridges are also subject to tre- f. Frost Action. Frost heave in soil is caused mendous lateral loads when an ice jam occurs at by the growth of ice lenses between the soil par- the bridge. ticles. Footings located above the frost line may i. Thermal Forces from Superstructures. On suffer from the effects of frost heave and a loss structureswithoutexpansionbearings,or in bearing capacity due to the subsequent soft-. where the expansion bearings fail to operate, ening of the soil. The vertical elements on light thermal forces may tip the substructure units. trestle bents may also be lifted by frost and ice Pavement thrust is another force that will have actions. the same effect. g. Expansive Soils. Some clays, when wet, ab- j. Drag Forces. Additional embankment loads sorb water and expand, placing large horizontal or very slow consolidation of a subsurface com- pressures on any wall retaining such soil. Struc pressible stratum will exert vertical drag forces tures founded on expansive clay may also expe- on the bearing piles which are driven through rience vertical soil movements (reverse settle- such material. This may cause yielding or fail- ment). bre of the piles (fig. 5-33).

5-20 Figure 5-81.Bearing failure.

k. Deterioration, Insect Attacks, and Con- 1. Scour (Erosion). Scour can cause extensive struction Defects. All piles may develop weak- settlement. Since water will carry off particles nesses leading to foundation settlements from of soil in suspension, a considerable hole can be one or more of these causes : formed around piers or other similar structural (1) Timber, steel, and concrete piles are objects. This condition results in a greater tur- subject to loss of section because of decay, rust- bulence of the water and an increased size of ing, and deterioration. soil particles that can be displaced. (2) Timber piles are vulnerable to marine m. Earth, or Rock Embankments (Stock- borers and ship worms. piles). Post-construction placement of embankments may cause instability since it will pro- (3)Constructiondefectsincludeover- duce greater loads than were included in the driven piles, underdriven piles, failure to fill original design. pile shells completely with concrete, or imper- fect casings of a cast-inplace pile. Any of these 5-7.4 Effects on Structures. defects will produce a weaker pile. Settlement will probably be gradual in improperly driven The effects of foundation movements upon a piles or in piles with weak or voided concrete. structure will vary according to the following Piles suffering severe loss of section due to rust, factors : spalling, chemical action, or insect infestation a. Magnitude of Movements. All foundations may fail suddenly under an unusually heavy undergo some settlement, even if only elastic load. compression of ledge or piles. All sizable foot-

5-21 Pervious Bac kf t 0

SeepageFlow

Weepers

Figure 5-32.Seepage forces at an abutment. ings probably will experience a minute differ- little effect upon the structure. Settlements of ential settlement. However, very small founda- nearly one foot have been experienced by small tion movements have no effect. Simple struc- (70-foot) single span bridges with no sign of tures, and those with enough joints, will toler-. appreciable distress. ate even moderate differential displacements (2)Differential Settlement.Differential with little difficulty other than minor cracking settlements can produce serious distress in any and the binding of end dams. Movements of bridge. Where the differential settlement occurs large magnitudes, especially when differential, between different substructure units, the mag- cause distress in nearly all structures (see Dif- nitude of the damage depends on the bridge ferential Settlement). Large movements will type and span length. Should a differential set- cause deck joints to jam ; slabs to crack; bear- tlement take place beneath the footings of the ings to shift ; substructures to crack, rotate, or same substructure, damage can varyfrom an slide; and superstructures to crack, buckle, and, opening of the vertical expansion joints be- possibly, even to collapse. The larger the settle- tween the wing wall and the abutment, to se- ment to be accommodated within a given dis- vere tipping and cracking of walls orother tance, the more structural damage can be antici- members. Scour, as shown in figures 5-34 and pated. 5-35, can cause complete failure. b. Types of Settlements. e. Types of Structure. (1) Uniform Settlement. A uniform settle- (1) Simple (Determinate). As mentioned Iment of all the foundations of a bridge will have above, the strength of a simple, or determinate, 5-22 JLII I I It

Fill

Adhesion of clay to piles allows consolidating soil to drag doWn on piles Silty Sand

L. Silt

=Soft Clay

SI I t Soft Clay

Figure 5-33.Drag forces on piles. structure usually is not affected by movements displacements which are greater in magnitude, unless they are quite large. There are usually or different in direction, from those that were enough joints to permit the movements without considered in the original designs. major damage to the basic integrity of the structure. At most, some finger joints or bearings may require resetting, or beam supports 5-7.5 What to Look for During Inspection. may need shimming. However, pile bent or tres- Foundation me-rementi may 'often be detected tle bridges are very vulnerable since a large set- by first looking for deviations from the proper tlement or movement of a bent could cause the geometry of the bridge. With the exception of superstructure to fall off a narrow bridge seat, curved structures, haunched members, and leading to the loss of the bridge spans. steeply inclined bridges, members and lines (2) Indeterminate Bridges. An indetermi- should usually be either parallel or perpendicu- nate bridge is seriously affected by differential lar to each other. While not always .practical, movements., since such movements at supports especially for bridges spanning large bodies of will redistribute the loads, possibly causing water or for those located in urban industrial large overstresses. For example, a fixed-ended areas, careful observation of the overall struc- arch could be severely damaged if a foundation ture for lines that seem incongruous with the rotates. Most continuous bridges have fewer rest of the bridge is .a good starting point. For a joints than simple span bridges. These bridges more detailed inspection, the following methods are very likely to be damaged if subjected to are often usefu:!

5-23 ment. For small bridges and for preliminary checks, the use of a plumb bob is an adequate means for determining plumbness. e.Observe the Inclinationof Expansion Rockers or Roller Movements. Rocker inclina- tions inconsistent with seasonal weather conditions may be a sign of foundation or superstructure movement. Of course, this condition may also indicate that the expansion rockers were set improperly. Out-of-plumb hangers on cantilevered structures are another indication of foundation shifting. f. Observe Expansion Joints at Abutments and Walls. Observe the expansion joints for signs of opening or rotating. These conditions may indicate the movement of subsurface soils or a bearing failure under one of the footings.

..v g. Check Deck Joints and Finger Dams.Ab- normally large or small openings, elevation dif- f ferential, or jamming of the.finger dams can be caused by substructure movements. Soil movements under the approach fills are also frequent Figure 5-34.Pier settlement due to scour. Note pier and deck cracking. occurrences. h.ObserveSlabs,Walls,and Members. a. Check the Alignment. Any abrupt change Cracks, buckling, and other serious distortions or kink in the alignment of the bridge may indi- should be noted. Bracing, as well as the main cate a lateral movement of a pier or of bearings. supporting sections, should be scrutinized for Older bridges are particularly vulnerable to ice distortion. pressures which can cause structural misalign- i. Check Backwalls and Beam Ends. Check ment. the backwalls for cracking which may be caused b. Sight Along Railings. A sudden dip in the by either abutment rotation, sliding, or pave"- rail line is often the result of settlement of a ment thrust. Check for beam ends which are pier or abutment. bearing against the backwall. This condition is c. Run Profile Levels Along the Centerline a sign of horizontal movement of the abutment. and /or the Gutter Lines. This inspection tech- 5. Observe Fill and Excavation Slopes. Slide nique will not only help to establish the exist- scarps, fresh sloughs, and seepage are indica- ence of any settlement, but will also identify tions of past or imminent soil movement. any differential settlements across the roadway. .Normally this kind of inspection technique will k. Scour (See Waterways, Section 5-26), be employed only for large bridges or where 1. Unbalanced Post-Construction Embank- information concerning the extent and charac- ment or Fills. Embankments or fills should be ter of differential settlement movement is re- checked for balance and positioning. Unbal- quired. anced embankments or fills can cause a variety d. Check Piers, Pile Bents, and. Abutment of soil movements which may impair theestruc- Faces for Plumbnes.s with a Transit. This tural integrity,of the bridge. inspection method provides an excellent check m. Underwater Investigation of All Piling for the simpler techniques of plumbness deter-. and Pile Bents. Underwater investigation of.>"- mination. An out-of-plumb pier in either direc- piling and pile bents should be undertaken peri- tion usually signifies foundation movement ;it odically. Check all timber piles for insect attack may also indicate a superstructure displace- and deterioration. Examine steelpiles well

5-24 11015,,,

ftwo, - 'Ir.Mill _ 'low= -411Par J

111/1111111011r lvt, III 4.ii,;o0t*It et litf tritak+v ww=1.

-% ER s 44 7

Figure 5-35.Abutment failure due to scour. Note buckling of end posts and bottom chord, and failure of portal knee brace connection.

below the water surface. Steel piles protected in for the bridge and retain the approach embank- the splash zone can rust between the concrete ment. jacket and the mud line. Examine pre-stressed b.Construction.Abutments may be con- piles belew water for cracking or splitting. structed of plain concrete, reinforced concrete, stone masonry, or a combination of concrete Section8.ABUTMENTS and _stone .masonry. Plain concrete and stone masonry abutments are usually gravity struc- 5 -8.1 General. tures, while reinforced concrete abutments are The term "abutment" is usually -applied to the mostly cantilever or counterfort types. substructure units at the ends of bridges; but- ments are classified according to their locations 5-8.2 What to Look for During Inspection. as full height (shoulder), semi-stub, stub, or a. Check for scour or erosion around the spill- through abutments. Figures 5-36, 5-37, abutment, and for evidence of any movement and 5-38 show different types of abutments. . (sliding, rotation, etc.), or settlement. Open a. Function. Abutments provide end support cracks between adjoining wing walls or in the

5-25 130c/two&

Bridge Seal

O 1 Breastrvai17.

Footinga.

FULL HEIGHT ABUTMENT

Backwa Bridge Seat Bridge Seat -;

Wing7 Breast Wall Breast Wall

Footing Fooling-a_r7; A '

STUB ABUTMENT

,-Dockwall Backwall sN\N. Bridge Seal'? pridge5eat --- Cap Beam Wing 7 Cap BEtim- .9

-2-Column Column

Fooling.? Footing 9

OPEN ABUTMENT.

Figure 5-36.Types of abutments.

5-26 abutment stem, off centered bearings, or inade- larly critical where concrete beams bear di- quate or abnormal clearances between the back rectly on the abutment. Check bearing seats for wall and the end beams are indications of prob- presence of debris and standing water. able movement (fig. 5-39). d. Check for deteriorating concrete in areas b. Determine whether drains and weepholes that are exposed to roadway drainage. This is are clear and functioning properly. Seepage of especially important in areas where deicing water through joints and cracks may indicate chemicals are used. accumulation of water behind t1;e abutment. e. Check- backwalls for cracking and possible Report any frozen or plugged weep holes. movement. Check particularly the construction Mounds of earth immediately adjacent to weep- joint between the backwall and the abutment. ers may indicate the presence of burrowing f. Check stone masonry for mortar cracks, animals. vegetation, water seepage through the cracks, c. Check bearing seats for cracking and spall- loose or missing stones, weathering, and spalled ing, especially near the edges. This is particu- or split blocks.

Y.,

AL.16,.faalba'f.'W

Figure 5-37.Fu. 11-height concrete abutment.

5-27 L

4. . ,...,.:..`,-i.,44,tleg.t.' v''+ -te...... ,

I . 74 ao...... 4 ;*;* ' 4' 4 744.4;,.41ct. , j% - ....4.4... t,...41.... 9::-.41;ei, ,..agrk:!..r,- a, ' , ,....% ,. , -: ..464' 7%4.14,,t".4:':...... rf5,...,,,,,,,41.. A.4.',!, .. N... r ` or,' " ...... 0.44' . .1 .0. ' r1.41;f4.,...7 1":"" 1" ,.:,....,9.4' .1,.4 41671,1;4i.4 ....e ., t ,.4_- ,,.".. ... S- ' .'''.. 7 : ' '''14' 71.;.? .- -, 7 _,- --,- ':_ ,. "..,!..,46 ...i.i -. tiOt_....G.,IT:II,1.14^ ,:-rt4... IA, ',....",;, 1-,:iik'i'/,4S3M1%"...... - ,-,..jp,,, t ,,,,,,..... ,...va ...... - ..--4,444; .."' '''.14:ti,,,akt ,Z.,,. '....:: . 114:4:61;6:a., ----4 . _,,,.... , ,...... R , 1,,,,,, -,,,,,.-. ...:,,t5.. , .....,,,,,.....,, , 'fl: '' :""....,1. :"iiply701:`:-.,-*. . .. ,, . 0 1 r. kt ,.'":.1.,:l....-;:m , ..N W.7. 1.. -.1 , C!'.."4 '... N ...... ,'%:',a..k..i,- .N.' . 'r., 4)=-" .-0.1.1. . . --:`....1.'-'.7.i Figure 5-38.Concrete and stone masonry stub abutment. Bockwo// Check for lippinq Check construction join/ or rotation for evidence of movement

Check construction join/ for spallinq

for ,t02 Check c/eorance Sealcpnci- beiween beam kaori0A led and bockwall 14 or 5r G..1.,60 cl.ce 6'0

e "."0/A Pcveq,, e:5. '70/ez, see. "74940/

Figure 5-39.Abutment checklist items.

Section 9.RETAINING WALLS tation. Straight wing walls are extensions of the abutment wall, flared wing walls form an 5-9.1 General. acute angle with the axis of the bridge road- Retaining walls are designed to maintain a dif- way, and U wings are parallel to the roadway. ference in the elevation between the ground The granite-faced walls in figure 5-38 are U surfaces on the two sides of the wall. The earth wings while flared wings are shown in figure whose surface is at the higher elevation is com- 5-37.

monly called "backfill". The retaining wall is a . b. Crib walls. Crib walls are composed of in- modification of the abutment since it is not re- terlocking precast or prefabricated members. quired to carry any vertical loads. The absence The crib resists overturning by tensile forces in- of the vertical superstructure load usually also the anchoring pieces, or deadmen, which extend requires a wider footing to resist the large net from the surface backward into the fill. Crib overturning moment carried by a retaining walls are made of : wall. (1) Timber. Old railroad structures often a. Wing walls. Wing walls are the walls on used crib walls made of railroad ties. the sides of an abutment which enclose the ap- (2) Precast concrete., proach fill. Wings are classified as straight, (3) Steel. Steel crib walls are actually cor- flared, or U wings, depending upon their orien- rugated bin -4.,ype retaining walls.

5-29 5-9.2 Matto Look for During Inspections. Section 10.PIERS AND BENTS Inspection of most retaining walls should be similar to that of an abutment. Crib walls are 5-10,1 General. subject to the same types of deterioration as other structures of wood, concrete, and steel. Piers and bents provide intermediate support to a. Settlement of the soil under the embank- the bridge superstructures(figs.5-40 and ment will lead to distortion and possible damage 5-41). They may be composed of plain or rein- to a crib wall. If sufficient movement occurs, the forced concrete, stone masonry, steel, timber, or wall may fail. a combination of these materials. Figure 5-42 exhibits the different types of piers. b. Timber cribs may decay or be attacked by termites. However, the creosote treatment is usually very effective in protecting the wood. 5 -10.2 What to Look for During Inspection. c. Concrete cribs are subject to chipping and a. Check for erosion or undermining of the spalling. In addition, the locking keys or flanges foundation by scour, and for exposed piles at the ends of the crib pieces are sometimes (figure 5-43). Check for evidence of tilt or set- broken off by vandals or inadvertently damaged tlement. (See the discussion of "Foundations" by casual passers-by. in Section 5-7.)

Figure 5-40.Solid concrete pier.

5-30 Figure 5-41.Column piers with solid web walls.

b. Check for disintegration of the concrete, I.Investigate any significant changesin especially in the splash zone, at the water line, clearance for pier movement. at the ground line, and wherever concrete is exposed to roadway drainage (fig. 5-44). j. CheCk all pier and bent members for structural damage cfinged by collision or overstress. c. Check the pier columns and the pier caps for cracks. k. Where a steel cap girder and continuous d. Check the bearing seats for cracking and longitudinal beams are framed together, check spalling. the top flanges, welds, and webs for cracking. e. Check stone masonry piers and bents for I. Observe and determine whether unusual mortar cracks, water and vegetation in the movement occurs in any of the bent members cracks, and for spalled, split, loose, or missing during passage of heavy loads.

f. Check steel : iers and bents for corrosion m. Where rocker bents(fig. 5-45)an-2de- (rust), especially at joints and splices. Bolt- signed to rotate freely on pins and bearings, heads, rivet-heads, and nuts are very vulnerable check to see that such movement is notre- to rust,_ especially if located underwater or in strained. Restr,int can be caused by severe cor- the base of a column. rosion or the presence of foreign particles. g. Examine grout pads and pedestals for n. Determine whether any earth or rock :ills cracks, spalls or deterioration. have been piled against piers causing loads not h. Examine steel piles both in the splash zone provided for in the original design and produc- and below water surface. ing unstable conditions.

5-31 Beni Cap Pier Cop 2..

Pier Wall Concrele Pile

Foo/inq

PILE BENT SOLID PIER

Pier Cop z_.. Pier Cop a._

--2-Column Column

Web Wall a

Footing -a__ Foohnqz_

COLUMN PIER WITH SOLID WEB WALL COLUMN BENT OR OPEN PIER

STEEL BENT CANTILEVER PIER OR HAMMERHEAD PIER Figure 5-42.Types of piers.

5-32 /Checl< bearing seals for cracked or spa/led concreie Check cop for deteriorated concrete

Check for plumbness---- Check columns and cap forcracks

Check for grolecl concrefe especially of the wafer line or croand line

Check for erosion orundermining

Figure 5-48.Concrete pier and bent checklist items.

5-33 Section I . PILE BENTS frgi*Fdi 5-11.1 General. .e Pile bents are transversestructural frame- works composed ofpiles and pile caps (fig. 5-47). The cap distributes the superstructure - r load to the piles and ensures that the piles act together. a. Function. Pile bents function as abutments or piers. When used as abutments the piles are usually completely below ground and the cap is cast integrally with the deck slab. b. Construction. Pile bents may consist of concrete, timber, or steel piles.

5-11.2 What to Look for During Inspection. a. Concrete. Check for the same items as discussed in Section 5-10, Piers and Bents. ;111 b. Timber, / t 4 (1) Check for decay in the piles, caps, and Figure 5-44. Steel beams on. concrete pier cap. Note bracing (fig. 5-47). The presence of decay nay disintegration of pier cap and deck brackets, exposure be determined by tapping with a hammer or by of reinforcement and corrosion of steel. test boring the timber. Check particularly at

A -; e` -t' _3k131tv,.

sommowill

j.ta,c, 44r" 54',4trr 44; glt le

>41, '41

eZ;

F; Jure 5-45.Rocker bent.

5-34 the ground line, or water line, and at joints and (7) Check timber piles in salt water to de- splices, since decay usually begins in these termine damage caused by marine borers. areas. (8)Check timber footing piles insalt water exposed by scour below the mud line for (2)Check splices and connections for damage caused by marine borers. tightness and for loose bolts. (9) Check timber piles in salt water at (3) Check the condition of the cap at those checks in the wood, bolt holes, daps or other points where the beams bear directly upon it, connections for damage by marine borers. and at those points where the cap bears directly upon the piles. Note particularly any splitting c. Steel. or crushing of the timber in these areas. (1) Check the pile bents for the presence of rust, especially at the ground level line. Use a (4) Observe caps that are under heavy chipping hammer, if necessary, to determine loads for excessive deflection. the extent of rust. Over water crossings, check (5) Check for rotted or damaged timbers the splash zone (2 feet above high tide or mean in the backwalls of end bents (abutments), es- water level) and the submerged part of the pecially where such conditions would allow piles for indications of rust. earth to spill upon the caps or stringers. Ap- (2) Check for debris around the pile bases. proach fill settlement at end bents may expoE.3 Debris will retain moisture and promote rust. short sections of piling to additional corrosior, (3) Check the steel caps for rotation due to or deterioration. eccentric connections. (6) In marine environments, check struc (4) Check the bracing for broken connec- tures for the presence of marine borers and tions and loose rivets or bolts. shipworms. (5) Check conditi.M of web stiffeners.

5-35 CROSS STRUT

Figure 5-46.Two column bent with cross struts.

5-36 Checkfor sPb/ling, crushing or decoy

)Check for -de decoy jz_(..1_:.z1 in soh' water oreo, check for marine borers

Check corinecii.%)ns for fiqh/riess and .1( loose arrnissin9 buffs

Figure 5-47.Timber bent checklist items.

Section 12. CONCRETE BEAMS AND GIRDERS 5-12.2 What to Look for During Inspection.

5-12.1 General. a, All Beams. Concrete beams and girders transfer deck loads (1) Check for spalling concrete, giving spe- to the substructures. The most common con- cial attention to points of bearing where fric- crete bridges are the slab, T-beam (fig. 5-48), tion from thermal movement and high edge I-beam, and box girder types. Box beams (fig. pressure may cause spalling (fig. 5-50). 5-49) and voided units are special types of the (2) Check for diagonal cracking, especially slab. The concrete slab serves as the floor of the near the supports. The presence of diagonal bridge as well as the top flange of the beams. cracks on the side of the beam may indicate The beams and deck may be cast as a single incipient shear failure. This is particularly im- monolithic sec-don or composed of individual portant on the older prestressed bridges. Canti- units, tied together by dowels, diaphragms, and lever box girder bridges, whether of prestressed end beams. The beams may be either conven- or reinforced concrete, utilize a shiplapped joint tionally reinforced or prestressed ; precast or in which the suspended span rests upon bear- cast-in-place. ings located on the anchor span. Figure 5-51

5-37 Figure 5-48.Continuous concrete T-bealu, bridge. illustrates such a joint. The shiplap cantilevers (2) Check the soffit of the lower slab and with re-entrant corners should be inspected the outside face of the girders for excessive very carefully for signs of cracking or other cracking. deterioration. (3) Check diaphragms for cracks. (3) Check for flexure (vertical) cracks or disintegration of the concrete, especially in the (4) Examine the underside of the slab and area of the tension steel. Discoloration of the top flange for scaling, spalling, and cracking as concrete surface may be an indication of con- described in Section 20 of this Chapter. crete deterioration or the corrosion of the rein- (5) Note any offset at the hinges which forcing steel. In severe cases, the reinforcing might indicate problems with the hinge bear- steel may become exposed. ing. An abnormal offset should be investigated (4) Observe areas that are exposed to further to determine the cause and the severity roadway drainage for disintegrating concrete. of the condition. (5) Check for damage caused by collision c. Prestressed Concrete Bridges. or fire. (6) Note any excessive vibration or deflec- (1) Check for longitudinal cracks on all tion. flange surfaces. This may occur on older pre- b. Box Girders. stressed bridges where insufficient stirrups were provided. (1) Examines the inside of box girders for cracks and to see that the drains are open and (21 Examine the alignment of prestressed functioning properly. beams. 5-38 Figure 5-49.Prestressed concrete box beam bridge. (3) Check for cracking and spalling in the On pretensioned deck units, either box beams or area around the bearings and at the cast-in- voided units, check the underside during the place diaphragms where differential creep and passage of traffic to see whether any unit is humping of the beams may have some ill effects. acting independently of the others.

5-39 Check tap' flonqe as describedthicier concrete decks

Checkfor Vertical stirru,o diagonal crocking of beam ends

Al Cintension steel Check for spainq concrete Check for flexure crocks ono/ disintegration of concrete around tension steel Figure 5-50.Concrete beam checklist items.

5-40 - '5'4;2; , -We* ;t1 11,64. Figure 5-51.Ship-lapped cantilever between a reinforced concretebox and a prestressed concrete suspended span. Note stains causedby roadway drainage. This may be a source of future deterioration. connections may Section 13.STEEL BEAMS AND GIRDERS ered bridge spans. Joints and be either welded, riveted, bolted, orpinned (fig. 5-13.1 General. 5-53). classed c. The function of theintermediate vertical a. Steel beams and girders which are thin webs of as main members, transmit alldeck loads to the and longitudinal stiffeners on the large built-up members is to preventweb buck- substructure of the bridge. There are three gen- shear to the eral types of steel beams and girders : ling. Bearing stiffeners transmit (1) Rolled (Wide Flange) Sections. These web and prevent web crippling. may be either cover plated orplain, and are usually used in the construction of bridge spans 5-13.2 What to Look for DuringInspection. of 100 feet or loss (fig. 5-52). a. Inspect steel forcorrosion and deteriora- (2) Built-up Sections (Plate Girders). This tion(fig.5-54)especially at the following type of beam is normally used in the construc- places : tion of bridge spans of 70 feet or longerin (1) Along the upper flange length. (2) Around bolts and rivet heads (3) Steel Box Girders. These are used for certain special applications, e.g., where addi- (3) At gusset, diaphragm, andbracing tional torsional resistance is required. connections b. Steel beams and girders may be used in the (4) At cantilever hanger and pin connec- construction of simple, continuous, or cantilev- tions

5-41 . :Par11111W1111Mr an. umit sespeor r,ITZ .

Figure 5-52.Continuous steel guide-flange bridge.

(5) Under the deck joints and at any other c. Examine areas around rivets or bolts and points that may be exposed to roadway drain- along the seams of built-up members and age. splices for deterioration and signs of slippage. (6) At any point where two plates are in d. Check members for cleanliness and free- face to face contact and water can enter (such dom from debris, especially on the top side of as between a cover plate and a flange). If rust- the bottom flange. ing occurs at this interface, the expansive force e. Examine welds, weld terminations, and ad- created will be great enough to spread the jacent metal for cracks, particularly at : plates. (1) Unusual types of weld connections or (7) At the fitted end of stiffeners. connections to which access would have been (8) At the ends of beams where debris may difficult for the welder. have collected. (2) Connections transmitting heavy tor- b. If rusting and deterioration is evident, sional or in-plane moments to the members. check the members for possible reduced cross Typical connections of this type are: sectional area, using calipers, rulers, corrosion (a)Floor beam to girder connection, meters, or section templates. where either the floor beam or girder is contin-

5-42 Figurc 5-58.Riveted steel girder bridge. uous through the other. (Steel pier caps are a may result from overstress, collision, or fire special type of floor beam.) damage. If such a condition is present, its effect (b)Bracketscantileveredfrom the on structural safety of the bridge should be fascia beams (or any cantilever connection fully investigated. from a beam). (c) Moment splices. g. Check for wrinkles, waves, cracks, or dam- (d) Joints in rigid frame structures or age in the web and flanges of steel beams, par- in vie,rendeel-type bracing. ticularly near points of bearing. This condition may indicate overstressing. Check the stiffeners (3) Sudden changes in cross-section or con- for straightness and determine whether their figuration or other locations subject to stress connections are broken, buckled, or pulled from concentrations or fatigue loadings. the web. (4) Areas where vibration and movement could produce fatigue stress. h. Determine whether any unusual vibration (5) Longitudinalstiffenerconnections. or excessive deflections occur under the passage Whether these longitudinal stiffeners are also of heavy loads. welded to the transverse stiffeners or are purely i. On cantilevered bridges, check hinges and ornamental, the possibility of web and weld hangers to see that they are functioning freely cracking is high. and without restraint due to scoring, jamming, (6) At unusual type connections, on curved dirt, or corrosion. sections, re-entrant corners, and copes. (1) If a hanger link Is out-of-plumb beyond f. Check the general alignment by sighting the limits expected for normal temperature var- along the members. Misalignment or distortion iations, a further investigation should be made.

5-43 Check sliffeners r for straightness and soancl connection,

Check flanges for deierioralion and possible /ass of sec/ion Check for wrinkles or :'/outs in me web and flanges

Check bottom flanges for align/nen/ and po.ssibIe damage from colksion Check kvelo's, for crocks Figure 5-54.Steel girder checklist items. (2) Where a hanger has one end fixed rig- ers. This type of floor system can he made from idly to web by welding or bolting, so as to steel, timber, prestressed or reinforced concrete develop an eccentric hinge, the hanger will de- beams. Concrete and steel beams are discussed velop both bending and axial stresses. Examine in Sections 5-12 and 5-13. Bridge decks are dis- the web and the hanger adjacent to its fixed end cussed in Section 5-20. For longer span bridges for cracking. a stringer and floor beam network transfers the j. Check the wind locks for: deck load to the main girders or trusses (figs. 5-55 and 5-56). Where the long span bridge is (1) Excessive movement before engaging. sufficiently narrow, the secondh.y stringers are (2) Binding, jamming, or improper fit. often omitted and the deck slab is carried longi- k. Do not overlook the inside of box girders. tudinally between floor beams.

5-14.2 Functions and Composition. Section 14.FLOOR SYSTEMS a.Floor beams are transverse members which support the stringers and transmit the 5-14.1 General. load to the main girders or load carrying mem- Bridge decks are supported on -three different bers. Steel pier caps on reinforced concrete pier types of floor systems. The simplest floor system columns are a special type of floor beam. Floor is that in which the decking or slab is carried beams are usually rolled beams, built-up sec- directly on the main girders or primary string- tions, or trusses.

5-44 SHOP RIVETS

-1..'....- "' '4"1,iibt*- 'Cir".'4,....Y- 'rad"; . . !,,,,V",',_(" , ,-

ei.,.'-'''. .?: STRINGER --t.- B 0 LT S -20*-*/!-- V.,'-*'-% :.' ''.4.:4:i-X1 .4.1 t.4 4); 'Cr9.4?) rt--2.,,,..._;,,,

GIRDERS

BOLTEDSPLICE

-;1

IS 4 .4 -rt -rt f"-t. r7 ,rr ti3 3 .3 :.;-!4. It * *t -A.r11-

.M12.th'IA Figure 5-55.Steel girder and stringer bolted splice details. b. Stringers are longitudinal members which (3) Check the floor beams to determine if sw:n between floor beams or piers and abut.. they are twisted or swayed. This situation occa- ntents to provide deck support. Deck stringer's sionally develops as a result of the longitudinal are usually steel WF-beams, timber, concrete forces that are exerted by moving vehicles on T-beams, or prestressed concrete members. the floor beams. It occurs primarily on older structures where the floor beams are simply 5-14.3 What to Look for During Inspection. supported and where the stringers rest upon a. Floor Beams (fig. 5-57). the floor beam. (4)On end floor beams, examine the (1) The end connections of floor beams connections thoroughly for cracks in the welds should be checked carefully for corrosion. This is particularly critical on truss bridges where and for slipped rivets or bolts. the end connections are exposed to moisture and b. Stringers. deicing chemicals from the roadway. (1) Steel. (2) The top flange of floor beams should be (a) Check for rust or deterioration, es- checked for corrosion, especially near the end pecially around the top flange where moisture connections and at points of bearing. may accumulate from the floor above and at the

5-45 LATERAL BRACE

MAINGIRDER

NZ,,,;111/417,

.rtlirtitr-y4-

?;ajik:f; KNEE BRACE r-71r

cn Figure 5-56.Floor system of steel two-girder bridge. end connections around rivets, bolts, and bear- which the stringer bears direely upon the abut- ings. rnent and bent caps. (b) Check for sagging or canted string- (b)Check for horizontal cracks and ers. splitting, especially at the ends of stringers, (c) Inspect all stringer connections foz where they are often notched. loose fasteners and clip angles(fig.5-58). (c) Check for sagging or canted string- Where stringers are seated on clip angles check ers. for cracks in the floor beam web. (d). Check the bridging between the (2) Timber. stringers to determine whether it is tight and (a) Check for crushing ani decay, espe- functioning properly. cially along the top where the deAKing comes in (e) Check for accumulations of dirt and contact with the stringer, and at points at debris.

5-46 Check end conned/oh of floor beo/n5 for corrosion

Check for Check for corrosion coned or Sawing stringers

Figure 5-57.Steel floor beam and stringer checklist items.

5.-47 CLIP ANGLE

Courtesy of District of Columbia Highway Dept.

Figure 5-58.Stringer support connection. Note effect of corrosionon horizontal legs of clip angles. Note also loose connectionon utility pipe.

Section 15.TRUSSES channels by lacing bars (fig.5-61)and stay plates (fig.5-61)at the ends. While new per- 5-15.1 General. forated cover plates have replaced lacing, and a. Function,. A truss consists of members newer bridges sometimes use closed box sec- which are generally under axial loading only, tions, many other section types will be found. i e., tension or compression. Its greatest useful- Interior verticals and diagonals on old bridges ness is in bridges with relatively long spans may consist of relatively slender solid rods where dead load is a problem. Trusses are gen- when the member issubject only to tension. erally considered to be main members, butare When two opposing tension diagonals are pro- also used as floor beams or bracing (fig.5-59). vided in the panel of a truss, theyare termed b. Composition,. While most trusses are of "counters." steel, timber trusses are still used (fig.5-60). Truss members may be connected with rivets, 5-15.2 What to Look for During Inspection. bolts, or pins. Although the configuration of a. Steel trusses. trusses varies widely, the essential components (1) Rust and Deterioration. On through are common to all (fig. 2-10). Truss members trusses (fig.5-62)moisture and deicing chemi- may be built-up sections, rolled sections, tubing, cals from the roadway are often splashed on the pipe, eye bars, or solid rods. An earlier com- lower chord members and the members adja- monly used construction practice was to connect cent to the curb (fig.5-63and5-64).The mois-

5-48 ture and chemicals are retained at the connection and between the adjacent faces of eye bar heads, pin plates, etc., leading to rapid deterioration of the member. On riveted trusses, the horizontal surfaces and connections of lower chord members (fig. 5-65) are especially susceptible to corrosion. Debris tends to accumulate causing moisture and salt to be retained. Note any deformation caused by expanding rust on the inside surfaces of laminated oroverlap- ping plates. (2) Alignment of Truss Members. End posts and interior members are vulnerable to collision damage from passing vehicles. Buck- led, torn, or misaligned members may severely reduce the load-carrying capacity of the truss. Misalignment can be detected by sighting, along the roadway rail or curb and along the truss chord members. Investigate and report any abnormal deviations. ( (3) Overstressed Members.Local buckling indicates overstress of a compressionmember. Wrinkles or waves in the flanges, webs, or cover plates are common forms of buckling.Over- stress of a ductile tension membercould result section area Figure 5-59.Deck truss bridge. in localized contraction in the cross

Courtesy of Timber Structures, Inc. Figure 5-60.Timber truss. 5-49 UPPER CHORD

GUSSET PLATE

r STAY PLATE :,, A

r 4 1

LACING

-444N 44, 'A cs'

Figure 5-61.Truss details. of the member. This is usually accompanied by (d) Examine eyebar members for cracks flaking of the paint. in the eyes. (4) Loose Connections. Cracks in the paint ( el Determine whether the spacers on or displaced paint scabs around the joints and the pins are holding the eyebars and looped rods seams of gusset plates and other riveted or in their proper position. bolted connections may indicate looseness or (f)Check thephysicalcondition of slippage in the joints. Check rivets and bolts threaded members such as truss rods at turn- that appear defective. buckles. (5) Pins. Inspect pins for scoring and b. Timber Trusses. other signs of wear. Be sure that spacers, nuts, retaining caps, and keys are in place. (1) Check for weathering, checking, split- (6) Noise. Note clashing of metal with the ting, and decay, Decay is often found at joints, passage of live loads. caps, and around bolt holes. Decay isalso common on the bridge seat. (7) Tension Members. (a) Check each truss where thereis (2) Check for crushing at the ends of com- more than one section in any tension member to pression chord and diagonal members. see that stresses are evenly divided. (3) Examine splices carefully for decay. (b) Check counter members to see that Note whether bolts and connections are tight. they are in proper adjustment. (4) Check for decay at joints where there (c) Check looped rod tension members are contact surfaces, daps where moisture can for abnormal cracking where theloci)is enter, and around holes through which truss formed. bolts are fitted.

5-50 Figure 5-62.Continuous through truss bridge.

(5) Check end panel joints for decay. (9) Be particularly aware of fire hazards, (6) Check for dirt or debris accumulation such as: on the bridge seat. (a) Brush or drift accumulating under (7) Investigate the roof and sides of cov- the bridge. ered bridges for adequacy of protection af- forded the structural members from the ele- (b)Storageof combustible material ments of weather. under the bridge. (8) Check the alignment of the truss. Sag- (c) Parking of vehicles under the bridge. ging of the truss may be due to the partial failure of joints or improper adjustment of steel (d) Signs of fires built by vagrants, chil- vertical rods. dren, or workmen under the bridge.

5-51 PANEL POINT PIN CONNECTION

LOWER CHORD EYE BARS

FLOOR BEAM CONNECTION

Figure 5-68.Detail of lower chord panel point connection.Note that the pin connection and floor beam connection beneath (treexposed to moisture and brine splashed from the roadway.

5-52 PANEL POINT PIN CONNECTION

LOWER CHORD EYE BARS

ROADWAY CURB

Figure 5-64. Lower chord pin connection of eyebar truss. This type of connection is particularly susceptible to the effects of ,inoisture and brine splashed front the roadway.

Section 16.DIAPHRAGMS AND CROSS FRAMES

5-16.1 General. a.Function.Diaphragmsaretransverse members between the main beams, or stringers, which brace and stiffen the beams. They distribute loads laterally and resist torsion. The lower chord of a cross frame also serves as the strut in the i,c,ttom lateral bracing. End diaphragms support the end of the bridge deck slab and transmit lateral forces to the bearings. Where a heavy concrete deck is used, the main function of a diaphragm is to brace the beams prior to the casting of the deck. b. Construction. Diaphragms on shallow steel stringer bridges are usually channel or wide flange beam sections connected to the stringer webs with plates or angles. Cross frames of Figure 5-65.Panel point connections alonglower structural tees or angles connected to stiffeners chord. Note the collection of debris along the horizontal are commonly used on the deeper built-up surface of the bottom chord. beams. Concrete diaphragms cast monolithi-

5-53 Check for hen/ or broken connedions between the web of /he beam and the diophragim

Check for rust or deierioroiion ()Pound rivets and bolts and where the end diaphragm comes in,COrneociwith the bridge Roar

Figure 5-66.Diaphragm cftecklist items. tally with the beams are ordinarily used on con- titularly susceptible to corrosion from roadway crete bridges. On prestressed bridges, a rod or moisture and from deicing agents. cable is sometimes threaded through the dia- (3)Look for buckled or twisted cross phragms to tie the beams to ;ether. frames. This situation may be an indication of overstress of the bracing. 5-16.2 What to Look for During Inspection. b. Timber. a. Steel. (1) Check for cracking or splitting, espe- (1) Check for loose or broken connections cially in end diaphragms that are supporting between the web of the beam or girder and the the floor. diaphragm (fig. 5-66). (2) Check for decay along the top of the (2) Check for rust or other deterioration, diaphragms where they come in contact with especially around rivets and bolts, and those the floor. portions of the end diaphragms which come in c. Concrete. Check for cracks, spalls, and for c(.1 Act with the bridge floor. These may be par- other forms of deterioration.

5-54 Section 17. LATERAL BRACING PORTALS AND Therefore, unless the girdersare very deep, SWAYFRAMES only a lower lateral system is provided. The upper bracing, if present, is normally for con- 5-17.1 General. struction purposes only. In the lower lateral a. Function. Bracing, the secondary system of bracing system, the floor beamsor the cross member,, distributes loads, stabilizes the bridge frames serve as transverse struts; the lateral against torsional and wind loadings, prevents truss is formed by merely adding the diagonal buckling of compression chords, and integrates members. On through trusses, the upper lateral the separate main member systems. truss is formed by the sway frame and portals b. Types. in conjunction with the lateral bracing diagonals. Figures 5-69, 5-70, and 5-71 illustrate the (1) Diaphragms. Diaphragmsaredis- details of a lateral bracing system. cussed in Section 5-16. (2) Lateral Bracing. On spans longer than (3) Portals and Sway Frames. Portals and 125 feet, a horizontal or lateral truss system sway frames are used to resist the sway and (figs. 5-67 and 5-68) is provided to resist wind torsional effects of wind loads and other lateral loads and to ensure a stable and rigid structure. forces. The portal is the heavy sway frame or A truss bridge usually hasa lateral truss at girder across the top of the end posts of through both the upper and lower chord levels. On large trusses (figs. 2-10 and 5-72). The portal maingirder bridges the concrete deck, together with tains the shape of the end cross section of the the stringers and floor beams, generally serves bridge and helps transfer the upper lateral the function of the upper lateral truss system. forces to the bearings. Through girder bridges

Figure 5-67.Deck truss lateral bracing system.

5-55 LATERAL BRACING

4.4 -fit $ f

Figure 5.-68.Lateral bracing system on steel two-girder bridge.

often use knee braces which laterally support c. Look for loose or broken connections. the top flange of the girder. d. Check all upper and lower bracing mem- c. Composition. Lateral bracing consists of bers to observe whether they are properly ad- angles, structural tees, pipes, tubes, wide-flange justed and functioning satisfactorily. sections, or built up sections composed of channels, angles, and plates. The sway frames and e. Check for bent or twisted members. Since portals are usually IC-frames, or X-frames made most of these bracing members work in com- of angles, tees, rolled beams, or a combination pression, bends or kinks could significantly of members and are as deep as clearances per- reduce their effectiveness. Since portals and mit. sway bracesnecessarilyrestrictclearances, they are particularly vulnerable to damage 5-17.2 What to Look for During Inspection. from high loads. a. Check all bracing members for rust, espe- f. Where lateral bracing is welded to girder cially on horizontal surfaces such as those of flanges, inspect the welds and flanges for crack- lateral gusset plates and pockets without drains ing. or with clogged drains. g. Observe transverse vibration or movement b. Check for rust around bolts and rivet of the structure under traffic to determine ade- heads. quacy of lateral and sway bracing. 5-56 UPPER CHORD LATERAL STRUT

UPPER LATERAL

Figure 5-69.Detail of sway brace and lateral strut connection.

5-57 STRINGER

414 's

LATERAL GUSSET PLATE

:3'erso , r '4" 4. "4- It 3:4,4C: 't t ---..c.t., Y,/,',,1/41.-d -

LOWERCHORD

showing lateral bracingconnections. Figure 5-70.Lower chord panel point

5-58 TOP LATERALS

LATERAL STRUT

UPPER CHORD

"E--- PORTALS

Figure 5-71.Upper lateral system of through truss.

5-59 PORTAL

r10. k el& A ri FAIIITAvA YA 16151K wa.. AOYAVATAF END POST

Figure 5-72.End view of truss showing portal members and end posts.

Section 78. METAL BEARINGS to resist vertical uplift. A number of different types of fixed and expansion bearing devices are 5-18.1 General. used in bridge construction. Typical examples are illustrated in figures 5-73, 5-74, and 5-75.

Bearings transmit and distribute thesuper- 5-18.2 What to Look for During Inspection. structure loads to the substructure, and they permit the superstructure to undergo necessary In examining these types of bearings, deter- movements without developing harmful over- mine initially whether they are actually per- stresses. Bearings are of two general types, forming the functions for which they have been fixed and expansion. The principal difference designed. Bearings should be carefully exam- between these bearing types is that fixed bear- ined after unusual occurrences such as heavy ings resist translation, to permit rotation of the traffic damage, earthquakes or batterings from superstructure, while expansion bearings per- debris in flood periods. Bearings should be in- mit both rotation and translation of the super- spected for the following: structure. Except on very short spans, bearings -a. Checl: that rockers, pins, and rollers are are usually designed to permit small amounts of free of ccrrosion and debris. Excessive corro- end rotation, Depending on structural require- sion may cause the bearing to "freeze" or lock ments, the bearings may or may not be designed and become incapable of movement. When

5-60 1

ROCKER

k 4`' ;at:

Figure 5-73.Expansion rocker bearing on pier.

movement of expansion bearings is inhibited, plates. This condition is common on bridges temperature forces can reach enormous values. that are located in salt air environments. b. Rocker bearings where slots are provided g. Detection of bearing rattles under live load for anchor bolts, should be checked to ensure conditions usually indicates that the bearings that the bolt is not frozen to the bearing. are loose. Determine the cause of this condition. c. Check that the bearing surfaces of rockers h. Check anchor bolts for looseness or miss- and rollers and the deflection slots around pins ing nuts. are clean and free of corrosion. i. Measure the rocker tilt to the nearest 1/8" d. Determine whether the bearings are in offset from the reference line as shown in figure proper alignment, in complete contact across 5-77. The appropriate amount of rocker tilt de- the bearings surface, and that the bearing sur- pends upon the temperature at the time of ob- faces are clean. servation. Most rockers are set to be vertical at e. Check bearings that require lubricants for 68°F for steel bridges. Record the temperature proper functioning to ensure adequate and at the time of inspection. proper lubrication. j. Measure the horizontal travel of the sliding f. In those cases where bronze sliding plates bearings to the nearest 1/8 inch from the refer- (fig. 5-76) are used, look for signs of electro- ence point. The two punch holes are aligned lytic corrosion between the bronze and steel vertically at the standard of temperature used

5-61 Figure 5-74.Expansion roller bearings on abutment. (usually 68°F). Record the temperature at the time of inspection. k. On skewed bridges, bearings and lateral shear keys should be checked to determine if either are binding or if they have suffered damage from the creep effect of the bridge.

1. Check cantilever girder hanger connections (fig. 5-78) and pin bearing connections (fig. 5-79) for corrosion and improper alignment.

Figure 5-75.Fixed bearing on pier.

5-62 Figure 5-76.Bronze plate expansion bearing at abutment. The lubricated bronze plate is hidden underneath the curved rocker plate.

5-63 Check oliqnmeni and cenferinq of the bearing and /hen' if is in complete contact across the bearioq surface. Check rocker bearings, for proper fit/ (see Chapiersec.r

Check that bearing surfaces ore clean and11 /7corroded

Match mark masonry pick, and bridge sea'

Figure 5-77.Metal bearing checklist items.

5-64 rf

1.7

Figure 5-78.Cantilever girder hanger connection. This typeof connection permits both translation androtation.

5-65 ment to pad thickness is 1 :4 for single pads. However, using a single pad thick enough to provide for the necessary movement couldre- sult in a large lateral or bulging deformation. To avoid this situation, steel platesare bonded between the pads of elastomer, restricting the bulge but permitting slight deformation. c. Problems. Possibly, the greatest problem encountered with elastomeric bearing pads con- cerns material which does not meet specified requirements. Elastomeric bearing pads of infe- rior quality may exhibit any of a number of defective signs, such as cracking, splitting, bulging, or tearing. A common defect ofpoor or improper fabrication results in the top and bottom surface of the pads not being parallel. This condition could result in unequalpressures on the pad. Any of the problems mentioned could result in the pad being unable to perform its WINDLOCK design function satisfactorily. Failure of the bearing pad to function properly could lead to deck distress and the transfer of additional and unique forces to the substructure which it may Figure 5-79.Cantilever girder with, direct bearing. not be able to sustain. After unusual occurr- Note windlock. ences such as heavy traffic damage, earthquake, or flood, the bearing pads should be examined carefully to assess the effect of such eventson Section 19. ELASTOMERIC BEARINGS the functioning of the pads. 5-19.1 General. 5-19.2 What to Look for During Inspection. a. Construction. Elastomeric bearing pads (fig. 5-80) are a type of expansion bearing a. Splitting or tearing, either vertically or device. They are made of a rubber-like material horizontally (fig. 5-82). This is often due to in- or elastomer molded in rectangular pads (fig. ferior quality pads. 5-81), or in strips. b. Bulging caused by excessive compression b. Function. When placed beneath a beam which may be the :result of poor material com- they permit moderate longitudinal movements position. and small rotations at the ends. On longer spans, two or more pads may be laminated with c. Variable thickness other than that which is steel plates between the pads to allow for due to the normal rotation of the bearing. greater movement without excessive bulging d. Note the physical condition of the bearing around the sides. Longitudinal movement is pads and any abnormal flattening which may accomplished by a shearing deformation of the indicate overloading or excessive unevenness of elastomer. The recommended ratio of displace- loading.

5-66 ANCHOR BOLT SOLE PLATE

T,,,sTT.? V.* 43

k w; , ,: 0 ELASTOMERICPADS;

4 Tit 401. s.

Or' , , Figure 5-80.Elastomeric bearing pad. Note steel sole plate.

5-67 Figure 5-81. Prestressed concrete bridgeon elastomeric bearing pad. Note key to prevent lateralmovement.

5-68 Check for Excessive euI9inq Splitting or Check for Tearing Uniform Thickness Longitudinal Movement

Bearing Seat

Figure 5-82.Elastomeric pad checklist items.

Section 20. DECKS concrete, and timber beams have all been used in composite construction. 5-20.1 General. b. Causes of Deterioration. Probably more a. Function. The primaryfunctions of the than any other part of the bridge, the deck is bridge deck are to provide a riding surface for subject to the adverse effects of traffic, weather- traffic and to transmit wheel loads to the under- ing, and chemical action. The repeated use of lyingsupportingmembers.Oncomposite deicing agents and abrasives on bridge decks is bridges, the concrete deck also serves as the top flange of the beams or girders. This is done by placing shear connectors along the interface between the beam and the slab. Steel, prestressed 2811111111111...-__

NOTE DEBRIS ACCUMULATION ON DECK

Figure 5-84.Transverse deck crack. Crack originated Figure 5-83.Longitudinal deck crack. at expansion joint in pan; pet. Note debris in gutter area. 5-69 a major cause of deterioration. Defective mate- (3) Cracking. While cracking is often due rials, inadequate design practices, and improper tomaterialorconstructiondefects,other construction methods also contribute to deterio- common causesare :foundation movement, ration. Where the beginning of deterioration is pavement thrust, a too-flexible design, failure of evident, it is important to take early remedial the supporting members, abrupt changes in action in order to avoid costly future repairs. reinforcement, and inadequate design. Figures 5-83, 5-84, and 5-85 show examples of deck 5-20.2 What to Look for During Inspection. cracks. (a) Deck Surface. Note the type, size, a. Concrete Decks. Check for cracking, scal- and location of cracks in the deck. Refer to Sec- ing, and spalling of the concrete and record the tion 5-1 for crack classification. extent of the deterioration. Refer to Section 5-1. (b) Deck Underside. Inspect the under- for guidance in describing these conditions. side of the deck for cracks and water leakage. (1) Scaling. Scaling is usually an indica- The passage of water through the deck usually tion of improper construction techniques or the causes some leaching of the concrete which use of defective material. It may also be the forms grayish-white deposits of calcium hy- result of inadequate maintenance or inadequate droxide in the area of the leak. Extensive water deck drainage. leakage may indicate segregated or porous con- (2) Spa lling. The extent of spalling can be crete, or a general deterioration of the deck. determined by tapping lightly with a hammer Areas of wet concrete are additional indications in the vicinity of the spall. A hollow sound indi- of defective concrete. cates a separatibn or fracture plane in the con- (c)WearingSurface.Examinethe crete beneath the surface. The hollow area wearing surface covering the concrete deck for should be marked, measured, and recorded. Ex- reflection cracking and for poor adherence to pansion joints and construction joints should be the concrete. Deteriorated concrete beneath the examined most thoroughly for spalling. In addi- wearing surface will often be reflected through tion to the previously mentioned causes, spalling may be the result of deck or foundation movement. This is a particularly likely cause if the joints are not properly closed. lir

c '11P14-* 1 lAW:

14,

. yoco t

e tt,

.re

. A.--;".. reto sip _--..2111E101 Figure 5-85. Transverse cracks. Note cracks are Figure 5-86.Rusted stay-in-place (S-I-P) forms. near inflection point, and are transverse even though deck is skewed. Note efflorescence.

5-70 the surfar?, in the form of map cracking. PGor welds or clips. Determine if there is any loss of adherence leads to development of potholes. If section due to rust or wear. deterioration is suspected, remove a small sec- (2) Slipperiness. Note whether decks are tion of the wearing surface in order to check slippery when wet. the condition of the concrete deck. (3) Utilities. If utilities are supported by (d) Stay-in-place (S-I-P) Forms. Re- the bridge, note any effect on the bridge. move several panels of the S-I-P forms, if d. Open-Grating Decks. cracking is suspected, to permit examination of the underside of the deck. Rusty forms (Pg. (1) Cracks. Examine the grating, support 5-86), water dripping from pinholes in the brackets and stringers for cracking of welds. form, or the separation of portions of the forms (2) Slipperiness. Note whether decks are from the deck are reliable indications of deck slippery when wet. Small steel studs may be cracking. welded to the grating in order to improve traction. (e) Reinforcing Steel.Note whether there are any stains on the concrete which would indicate that the reinforcing steel is Section 21. EXPANSION JOINTS rusting. Note whether any of the reinforcing steel is exposed. 5-21.1 General. (4) Wear. Determine whether the concrete Since all materials expand and contract with surface is worn or polished. When softer lime- changes in temperature, provisions must be stone aggregates are used in the concrete, fine made in the bridge superstructure to permit aggregates and paste will be worn away, expos- movement to take place without damage to the ing the surface of the coarse aggregates to the bridge. On very shortstructures, there is polishing action of rubber tires. The resulting usually sufficient yielding in the foundation to slippery surface becomes increasingly hazard- allow the small amount of movement to occur ous when the surface of the limestone is wet. without difficulty. On longer structures, however, specially designed expansion joints are b. Timber Decks. provided in the deck. Where only moderate (1) Deterioration. Check for loose, broken, amounts of movements are expected, the joint or worn planks, for loose fasteners, and for may be only an opening between abutting parts. presence of decay, particularly at the contact When a watertight seal is desired, a premolded point with the stringer where moisture accum- filler topped with a poured-in-place sealer (fig. ulates. Check asphalt overlays for the presence 5-87) or a preformed compression seal ia in- of potholes and cracking as a result of weak serted. Where traffic is heavy, the unprotected areas in the deck. edge of the joint is usually armored with steel (2) Observe the timber deck under passing angles set in the concrete. When larger move- traffic for looseness or excessive deflection of ments must be accommodated, a sliding plate or the members. finger plate expansion joint may be used (fig. (3) Slipperiness. Timber decks are some- 5-88). A trough is often provided beneath a times slippery, especially when wet. Observe the finger plate expansion joint to catch water from traction of vehicles using the bridge for signs of the roadway. this condition. (4) Utilities. If utilities are supported by 5-21.2 What to Look for. During Inspection. the bridge, note the effects on the bridge. a. Check all expansion joints for freedom of movemeLt, proper clearance, and proper verti- c. Steel Decks. cal alignment (fig. 5-89).There should be suffi- (1) Check for corrosion and cracked welds. cient room for expansion but the joint should Maintenance of an impervious surface over a not be unduly open. Closed or widely opened steel deck is an important safeguard against joints, or a bump at the back wall can result corrosion of the steel. Check to determine if the from substructure movements. The crowding of deck is securely fastened. Note any broken abutments against the bridge ends is common,

5-71 EMINVIMPEZI

Figure 5-87. Sealed deck joint. A premolded filler topped with a poured-in-place sealer has been used. Figure. 5-88.Finger plate expansion device.

data concerning the setting of expansion 'de- and can cause severe damage to the bridge. vices. Proper opening size depends on the season, the b. Check seals for water tightness and gen- type of joint seals, the temperature range, and eral conditions. Look for : the length of the slab whose expansion the joint (1) Seal or sealant pulling away from the must accommodate. Normal temperature is usu- edges of the joints. ally assumed to be 65° to 70°F. Table 5-1 lists (2) Abrasion, shriveling, or other physical some general data for various types of expan- deterioration of the seal. sion joints. The expansion length in table 5-1 (3) Stains and other signs of leakage un- is the portion of deck or structure whose ex- derneath the deck. Leaking seals permit water pansion must be accommodated by the joints. and brine to flow onto the bridge seat and pier This distance may extend from the end of the cap causing corrosion of bearings, disintegra- bridge to the nearest fixed bearing, or it may tion of concrete, and staining. Joints not prop- be the sum of the distance on both sides of the erly sealed should be cleaned and resealed. joint. Multiplying the expansion length by the c. Check to see that expansion joints are free differential between the temperature at the par- of stones and other debris. Stones lodged in the ticular moment and 68°F, and this product by joints can create localized stresses which may 0.0000065 will give the approximate change in cause cracking and spailing of the deck. Large joint openings from the values listed above. amounts of debris cause jamming, thus render- Very often, construction plans will give useful ing the joints ineffective. 5-72 Check the slob in the vicinity of fhe joini for cracking or spading

Check far stones ono' other debris wedged be /ween abutting ports

Check for proper amount Check sea/ far of joint opernn q frvaler hqhtness and genera/ Armorec/ joint (bpi/Ono/) C0/90/#10/7 Poured joint .sealer

Premoaded expansion joint filler

FigurC 5-89.Expansion joint checklist items.

Table 5-1. Expansion joint data. Joints Expansion Lengths Joint Openings at 68°F. Steel finger dams 200 feet or more 3 inches min. Steel expansion plates 200 feet maximum 2 inches Compression seals 135 feet maximum 1% inches Poured sealants and joint fillers 120 feet maximum 11 /2 inches

d. Examine steel finger type joints and slid- g.Sound the concrete deck adjacent to all ex- ing plate joints for evidence of loose anchor- pansion devices for voids or laminations in the ages, cracking or breaking of welds, or other deck. defective details. Sometimes the fingers may be damaged by traffic or by cracks which have developed at the base of the fingers. Section 22. RAILINGS, SIDEWALKS, AND CURBS e. Verify that surfacing material has not jammed the finger joints on bridges that have 5-22.1 General. been resurfaced several times. Railings, sidewalks, and curbs normally do not f. Examine specifically the underside of the contribute to the structural strength of the expansion joint, regardless of accessibility, to bridge. They are provided mainly for public detect any existing or potential problem. safety.

5-73 Figure 5-90.Concrete parapet and sidewalk with steel tubular rail (left) and concrete -median barrier (right).

a. Railings. Railings should be sufficiently 5-22.2 What to Look for During Inspection. strong to prevent an, out-of-control vehicle from a. Railings. going off t'he bridge. However, many existing (1) Inspect all railings for damage caused bridges have vehicle guard rails that are little by collision, and for weakening caused by some better than pedestrian handrails. Such guard form of deterioration: rails are inadequate for safety, are easily damaged by vehicles, and are susceptible to deterio- (2) Check concrete railings for cracking, ration. On the other hand, an unyielding guard disintegration, and"corrosion of rebars. rail poses a hazard to vehicular traffic particu- (3) Check steel and aluminum railings for larly if struck head on. Unprotected parapets loose posts or rails, and for rust and other dete- pose a similar danger. rioration. In particular, check the condition of the connections of the posts to the decks, includ- b. Narrow Roadway. Bridge roadways that ing the condition of the anchor bolts and the are narrower than the approach roadway are deck area around them. dangerous since they restrict vehicular maneu- (4) Check timber railings for decay, loose verability and can be the cause of accidents. connections, and for missing or damaged rails. c. Sidewalks.and Curbs. Sidewalks and curbs (5)Check the vertical and horizontal (fig. 5-90) are provided to protect pedestrians alignment of all handrails for any indications of crossing the bridge. In rural areas, often onlya settlement in the substructure or any bearing narrow curb is provided (fig. 5-91). deficiencies.

5-74 Figure 5-91.Concrete railing and curb. (6) Examine all handrail joints to see that stalled at both ends of the existing railings or they are open and functioning properly. parapets. (7) Examine all handrails to see that they (10) Examine barrier railings for traffic are of adequate height, secure, and relatively damage and alignment. free of slivers or any projections which would (11) -Check concrete barrier railings for be hazardous to pedestrians. cracks, spalls, and other deterioration. (8) Check for rust stains on the concrete (12) Check for corrosion in the metal por- around the perimeter of steel rail posts .ihich tions of barrier railings and determine whether are set in pockets. Remove grout from around the anchor bolts and nuts are tight. the posts and determine severity of corrosion if b. Sidewalks. rust stains indicate such action is warranted. (1) Check concrete sidewalks and parapets (9) Note whether barrier railings on the in the same manner as the bridge decks for approaches to bridges extend beyond the end of cracks (figs. 5-92,5-93, and 5-94), spalls, and the bridge railing or parapet end and are another deterioration. chored to the inside face. This feature reduces (2) Examine the condition of concrete the severity of vehicle collision. In situations sidewalks at joints, especially at the abutments, when parapet ends are unprotected (fig. 5-95), for signs of differential movement which could and no approach rail exists, a flared, tapered open the joint. approach railing should be installed. On two- (3) Check steel sidewalks for corrosion way bridges, this type of railing should be in- and to see that all connections are secure.

5-75 -

Figure 5-92.Transverse crack in sidewalk curb and deck. Note that crack extends through the granite curb.

(4) Check timber sidewalks for soundness (8) Check structural integrity of sidewalk of the timber. Determine whether the floor brackets. planks are adequately supported. c. Curbs. (5) Check timber sidewalks for hazards to pedestrians such as loose or missing planks, (1) Check concrete curbs for cracks (figs. large cracks, decay or warping of the planks, 5-92,5-93, and .5-94), spalls, and other deterio- protruding nails, or other hazardous conditions. ration. (6) Check slickness of surfaced timber (2) Check timber curbs for splitting, warp- during wet or frosty weather conditions to de- ing, and decay. termine whether any corrective action is neces- (3)Report any curbs or safety walks sary. which project into the roadway, or a narrow (7) Check sidewalk drainage for adequate shoulder of the roadway, since they are safety carry-off. Examine the sidewalk surface for hazards. roughness or other conditions thatmay make (4) Note any loss of curb height resulting walking hazardous or difficult. from the build-up of the deck surface.

5-76 ti ORNAMENTAL RUSTICATIONS

Figure 5-93.Cracks in sidewalk. Note crack going through slaband note efflorescence stains.

(5) Examine timber wheel guards includ- (7) Note condition of the painting oftim- ing scupper blocks for splits, checks, and decay. ber wheel guards where paintis used to im- (6) Check timber wheel guards to see prove visibility. whether they are bolted securely in place.

5-77 Figure 5-94.Crack through safety curb. Crack started at parapet joint and continued across curb and deck. See also figure 5-84. .

Section 23. APPROACHES subsoil and approach fills, while the bridge, supported on piles, does not settle at all. In either 5-23.1 General. case, periodic resurfacing may be necessary. a. Elevation Difference. A smooth transition One popular solution to this problem is the ap- between the roadway pavement and the bridge proach slab which spans the 15 to 25 feet of fill deck is important for the reduction of impact immediately behind the abutment. This mini- forces acting upon the bridge for safety, and mizes the effects of approach fill settlement and for driver comfort. A difference in elevation be- poor compaction. tween the bridge deck and the approach pave- b. Joint Width. The width of the joint at the ment increases impact and vibration as the ve- backwall (or at the other end of the approach hicle reaches the bridge. Rough approaches will slab) is also important. An abnormally closed also cause vibration in the vehicle which, in joint may indicate pavement thrust developing turn, transmits added vibration to the bridge. against the backwall. Pavement thrust is often rough approaches are usually the result of a caused by pebbles or debris filling pavement volume change either from settlement in the joints after contraction, thereby preventing the backfill material(resulting from inadequate joint from absorbing expansion. This causes the compaction) or from a general consolidation of total pavement length to increase and, eventu-

5-78 UNPROTECTED PARAPET differences in elevation across the joint not END VERY HAZARDOUS caused by the grade. If the deck is lower than the approach, or if the straight edge indicates a rotation, then foundation settlement or movement may have occurred, and other indications of such action should be checked. (2)Joint Width(Horizontal Displace- ment). (a)Incorrect Opening. Measure the joint width for either increased or decreased openings. Either condition indicates foundation movement. A decreased opening could also be caused by pavement thrust. Other parts of the bridge affected by such occurrences should also be investigated. (b) Clogged Joints. Where joints are clogged or jammed with stones and hard debris, the expansion joints will be unable to function properly, and pavement thrust will develop. Make particular note of this condition. (c)Joint Seal. The integrity of the joint sealant (fig; 5-95) is critical to protect- 'IlikingfersaMKRAPIA. ing the soil or portions of the bridge under the joint, particularly the bridge seat, from water. The seal may be damaged by either weathering, traffic abrasion, or movement of the seal itself. Figure 5-95. Sealed joints at bridge end between abut- b. Other Transverse Joints Near the Bridge. ment backwall and adjacent deck and approach slab. Examine these joints for closing or clogging, since they are liable to the same difficulties as ally, press against the bridge. If permitted to the backwall joints. The inspector should note persist, suc'n a condition-could lead to cracked the relative movements (if any) of the joints, backwalls, swilling of the abutment face in any clogging with stones or other debris, and front of the beam bearing anchor bolts, tipping any failure, deterioration, or slippage of the of piers, and arching of the slab above the joint seal. The extent of these defects should be beam. A closed joint could also indicate a back- reported. ward tipping of the abutment due to subsoil set- c. Approach Slabs. Check for cracking or tip- tlement. On the other hand, an abnormally wide ping of the approach slabs. These are indica- joint may indicate forward movement of the tions of poor backfill compaction (although, on abutment due to a movement of the supporting a skewed bridge, it would not be unusual for an soil or bending of piles under lateral earth pres- acute corner to crack). sures. This can easily occur under older spill- through type abutments. See Abutments, Rail- d. Shoulders and Drainage. Check the shoul- ings, Signing, Bridge Drainage, and Founda- ders and determine whether they are main- tion Movements for other discussion of defects tained at the same height as the pavement. which indirectly affect approaches. There should be adequate provisions to carry off drainage in catch basins or ditches, especially if 5-23.2 What to Look for During Inspection. water is allowed to flow off the bridge deck. a. At the Joint of the Bridge Backwall. e.Approach Slopes. Check the approach (1) VerticalDisplacement.Layinga slopes for adequacy and report any condition straight edge across the joint will record any 'which impairs their design function.

5-79 f. Pavement Approaches. Report any pot- Poor deck drainage usually leads to deck disin- holes, severe cracks, surface unevenness, or tegration. other surface defects that make the approach a. Clogging. Clogging is the most apparent unusually rough or indicate approach settle- problem. Clogging occurs at: ment. (1) Inlets. Debris and design oversights are principal causes for inlet clogging. The Section 24.BRIDGE DRAINAGE

5-24.1 General. Bridge drainageis an important inspection item since trapped or ponded water, especially in colder climates, can cause a great deal of damage to a bridge and is a safety hazard. Therefore, an effective system of drainage that carries the water away as quickly as possible is essential to the proper maintenance of the bridge (fig. 5-96).

5-24.2 Drainage Problems, Almost all of the drainage problems encountered by an inspector are caused by the failure of the drainage system to carry water away.

Figure 5-97.Roadway drain.

Figure 5-96%Deck drainage. Figure 5-98.Open pipe drain.

5-80 ponds, or puddles of water, that form on the may indicate leaky pipes, filled gutters, or scup- bridge deck pose the problems of hydroplaning per discharge pipes that are too short. (Stained and icing. Ponds, or puddles, constitute a szfety abutments and piers could also mean leaky hazard and can cause extensive bridge deterio- joints, however.) ration. Figures 5-97 and 5-98 show two types c. Drain Outlets. Check to see that deck drain of inlets. outlets(scuppers)do not discharge water (2) Downspouts. Downspouts and horizon- where it may be detrimental to other members tal runs which are poorly designed with inade- of the structure, cause fill and bank erosion, or quate slopes and sharp directional changes at spill onto a roadway below. the elbows are conducive to the plugging of d. Damaged Pipes. Look for pipes damaged drains. by freezing, corrosion; or collision. These will (3) Expansion Dams. The gutters under show cracks, holes, or stains. expansion dams fill up very rapidly, especially where roads are heavily sanded in winter. This e. Clogged Pipes. Check pipes,if possible. causes the storm water to overflow onto the Open the cleanout at bottom of pipes to see bearings, end diaphragms, pier caps, and bridge whether pipes are open all the way through. seats, resulting in severe rusting of the steel f. Sand or Soil Accumulations. Check for lay- and deterioration of the concrete. Of special ers of sand or sail on the bridge deck. Presence consequence is the deterioration and freezing of of either of these will retain moisture and expansion bearings and rollers. brine, and will accelerate deck scaling. Soil or b. Corrosion. Drainage water often carries sand deposits are clear indications of poor deck corrosive elements, particularly salt, that attack drainage. drainage pipes and concrete. Clogging and slow drainage accelerate corrosion. Section 25. DOV)HINS AND FENDERS c. Freezing. Water backed up in the drainage pipes may freeze and, possibly, rupture the 5-25.1 General. pipe. Where the pipe is cast into a pier or abut- Dolphins and fenders around bridges protect ment, the concrete member may also crack. the structure against collision by maneuvering d. Entrapped Water. Where a concrete deck vessels. The fender system absorbs the energy is covered with an asphaltic wearing surface, of physical contact with the vessel. the underlying concrete surface is liable to seri- a. Dolphin Types. ous deterioration by entrapped water. On some (1) Timber Pile Cluster Dolphins. This bridges drains have been placed under the type of dolphin consists of a cluster of timber wearing surface to avoid this situation. piles driven into the harbor bottom with the e. Short Scupper Pipes. On river bridges, tops pulled together and wrapped tightly with scuppers usually drain water directly into the wire rope (fig. 5-99). It is widely used. river. Where the discharge pipes are short or (2) Steel Tube Dolphins. Steel tube dol- nonexistent, drainage may splash or blow onto phins are composed of one or more steel tubes bridge members, causing corrosion. driven into the harbor bottom and connected at the top with bracing and fendering systems. 5-24.3 What to Look for During Inspection. (3) Caisson Dolphins. Caisson dolphins are a. Clogging or Inadequate Drainage Open- sandfilled, sheet-pile cylinders of large diame- inv. Check the deck and -the deck inlets for ter. The top is covered by a concrete slab, and signs of clogging or inadequate drainage open- fendering is attached to the outside of the ings. These deficiencies will be manifested by sheets. debris on, or around,_ the inlet after a storm. b. Fender Types. Scaling and concrete deterioration around the (1) Timber Bents. A series of timber piles inlet are additional signs of an inadequate inlet. with timber walers and braces attached to the b. Water Stains: Observe the bridge beams, pile tops are still used (fig. 5-100). Steel piles piers, and abutments for water stains. These are sometimes used in lieu of timber.

5-81 7er

21zr. Aix .fit =s- 14 iz.1 ,

Figure 5-99.Timber pile cluster dolphins and timber fender system on pier.

(2) Cofferdam Fenders. On large bridges (6)Floating Fenders. Floating frame- with wide footings, the cofferdam sheets left in works which partly or completely surround the place and braced by a concrete wall act as pier pier are sometimes used as fenders. The main protection. A grid or grillage of timber or other frames are usually made of steel or concrete resilient material on the outside of the sheets with timber cushioning on the outside face. forms a collision mat. (7) Butyl rubber may be used as a fender- (3) Steel Piles. Steel piles driven in pairs ing system. to form a frame, with a concrete slab tying the piles together, make a good fender. Timber gril- 5-25.2 Factors Causing Deterioration. lages are attached to the outside to absorb colli- a. Decay or Corrosion. In steel or concrete, sion impact. the deterioration is usually caused by the corro- (4) Steel or Concrete Frames. Steel or con-. sive effects of the water (especially sea water). crete frames are sometimes cantilevered from In timber, decay fungi and marine insects attack the pier and faced with a timber or rubber wood. cushioning, to reduce collision impact. b. Abrasion. Timber fenders are particularly vulnerable to abrasion. Abrasion damages the (5) Timber Grids. Timber grids, consisting wood and reduces the thickness of the treated of posts and walers, are attached directly to the layers protecting the wood. Metal and concrete pier (figs. 5-99 and 5-101). also suffer from abrasion.

5 -82 c.Uplift. Timber pile dolphins experience d. Weathering. Timber Well above the water failure by uplift of some of the piles under lat- line or water level is subject to weathering and eral loads and ice loads. deterioration,

Figure 5-100.Timber bent fenders.

t t

I- l C tl gi 5-25.3 What To Look For During Inspection. This includes breaks in the surface of treated a. Steel. Observe the "splash zone" carefully timbers, cracks in protective concrete layers, for severe rusting and pitting. The splash zone rust holes or tears in metal shields, And bare is the area from high tide to 2 feet above high areas where epoxy or coal tar preservatives tide. Where there are no tides, it is the area have been applied externally. from the mean water level to 2 feet above it. f. Catwalks. Note the condition of the cat- Rusting is much more severe here than at mid- walks for fender systems. tide elevations. b. Concrete. Look for spalling and cracking Section 26. WATERWAYS of concrete, and rusting of reinforcing steel. Be alert for hour-glass shaping of piles at the 5-26.1 General. water line. Waterways should be inspected in order to de- c. Timber. Observe the upper portions lying termine whether any condition exists that could between the high water and mud line for ma- cause damage to the bridge or to the area sur- rine insects and decay (fig. 5-102). Check the rounding the bridge. In addition to inspecting fender pieces exposed to collision forces for the channel's present condition, a record should signs of wear. be made of any significant changes that have d. Structure Damage. Check all dolphins or taken'place in the channel, attributable either to fenders for cracks, buckled or broken members, natural or artificial causes. When significant and any other signs of structural failures or changes have occurred an investigation must be damage froin marine traffic.. made into -the probable or potential effects on (1) Piling and walers require particular the bridge structure. Events which tend to pro- attention since these are areas most likely to be duce local scour, channel degradation, or bank erosion are of primary importance. damaged by impact. (2) Note any loose or broken cables which a. Scour. Scour is 'defined as the removal and would tend to destroy the effectiveness of the transportation of material from the bed and cluster.Note whethertheyshould bere- banks of rivers and streams as a result of the wrapped. erosive action of running water. Some general (3) Note missing walers, blocks, and bolts. scouring takes place in all stream beds, particularly at flood stage. The characteristics of the e. Protective Treatment. Note any protective channel influence the amount and nature of treatment that needs patching or replacing. scour. Accelerated local scouring occurs where there is an interference with the stream flow, e.g., approach embankments extended into the river or piers and abutments constructed on the river bottom. The amount of scour in such cases depends on the degree to which stream flow is disturbed by the bridge and on the susceptibil- ity of the river bottom to scour action. Scour depth may 'range from zero in hard rock to thirty feet or more in very unstable river bot- toms. In determining the depth of local scour, it is necessary to differentiate between true scour and apparent scour. As the water level subsides after flooding, the scour holes that are produced tend to refill with sediment. Elevations taken of the stream bed at this time will not usually reveal true scour depth. However, since material borne and deposited by water will usually be somewhat different in character from the mate- Figure 5-102.Limnoria attack of a timer dophin. rial in the substrata, it is often possible to de- _ 5-84 termine the scour depth on this basis. If, for gradually readjust itself to the changed condi- example, a strata of loose sand is found overly- tion and will tend to return to a regime condi- ing a hard till substratum, it is reasonable to tion: Stream bed degradation and scour seri- assume that the scour extends down. 'to the ously endanger bridges whose foundations are depth of the till. This can often be confirmed by located in erodible river bed deposits and where sounding or probing, provided the scour depth the foundation does not extend to a depth below is limited to a few feet. Where coarse deposits that of anticipated scour. Removal of material or clays are encountered, sounding will proba- adjacent to the foundation may produce lateral bly be unsuccessful. slope instability causing damage to the bridge. b. Stream Bed Degradation. Stream bed deg- Either concrete slope protection (fig. 5-103) or radation is usually due to artificial or natural riprap (fig. 5-104) is often provided to prevent alteration in the width, alignment, or profile of bank erosion or to streamline the flow at ob- the channel. These alterations which may take structions. It is particularly important where place at the bridge site or some distance up- flow velocities are higher or where considerable stream or downstream,. upset the equilibrium, turbulence is likely. It may also be necessary or regime, of the channel. A channel is said to where there is a change in direction of the wa- be in regime if the rate of flow is such that it terway. Slope cones around abutments are very neither picks up material from the bed nor de- susceptible to erosion and are usually protected. posits it. In the course of years she channel will c. Waterway Adequacy. Scour and stream bed

Figure 5 -103.Concrete lined channel.

5-85 degradation are actually the result of inade- board should bP considered in determining wa- quate waterway areas. The geometry of the terway adequacy. Where large quantities of de- channel, the amount of debris carried during bris and ice are expected, sufficient freeboard is high water periods, and the adequacy of free- of the greatest importance. 5-26.2 What to Look for During Inspection. a. Maximum Water Level. Ideally, waterways should be inspected during and immediately following periods of flood, since the effects of high water will be most apparent at these times. v; :i Since this is not always possible, a knowledge of i..,:sits.,, ..1...../., ...... 7,... the heights of past major floods from stream

...-P gauging records, or from other sources, to- -....--i..,..ket. tr . - N .-,.., .. K4 ... ,...,..,- -a - --- 14 .40 gether with observations made during or imme- .;',.' . ..mr- ....., ..e r ..r.,, ..... :.. '' ..7 ...(A ...: ' .. diately following high water, are helpful in de- W, 1.4e:;'-'/- 4(°1;e.i ;eii11'. :\ ...... termining the adequacy of the waterway open- ;*C' A...,in.-. , .- . 4'4 I': ":1".:-'4' . 0,4.. 7". 74.07,..,..".....,.....,....., ings. Other sources are : (1) High water marks or ice scars left on trees Figure 5-104. Slope cone protected by stone riprap. (2) Water marks on painted structures

Figure 5-105.Drift and debris deposited in channel following flood. 5-86 era (3) Debris wedged beneath the deck of the be taken in a radial pattern around the large bridge or on the bridge seats river piers. (4) Information from established local res- (3) Shore and Bank Protection. idents. (a) Examine the condition and adequacy b. Insufficient Freeboard. This is a prime of existing bank and shore protection. characteristic of inadequate waterways. In ad- (b) Check for bank or levee erosion dition to the signs mentioned previously, lateral caused by improper location or skew of the displacement of old superstructures is a prirm bridge piers or abutments. indication of insufficient freeboard. (c) Note whether channel changes are impairing or decreasing the effectiveness of the c. Debris. Debris compounds the problems of present protection. a scanty freeboard. Check for debris deposits (d) Determine whether it is advisable to along the banks upstream and around the add more channel protection or to revise the bridge (fig. 5-105). existing protection. d. Obstruction. Debris or vegetation in the f. High Backwater. Be particularly alert for waterways, both upstream and downstream, locations where high fills and inadequate or de- may reduce the width of the waterway, contrib- bris-jammed culverts may create a very high ute to scour, and even become a fire hazard. backwater. The fill acts as a darn, and with the Sand and gravel bars formed in the channel possibility of a washout during rainfall, a disas- may increase stream velocity and lead to scour trous failure could result (fig. 5-121). near piers and abutments. g. Observe the effect of wave action on the e. Scour. bridge and its approaches. (1) Channel Profile. In stream beds suscep- h. Observe the areas surrounding the bridge tible to scour and degradation, a channel profile and its approaches for any existing or potential should be taken periodically. Generally 100-foot problems, such as ice jams. intervals, extending to a few hundred feet upstream and downstream, should be sufficient. i. Observe the condition and functioning of This information, when compared with past existing spur dikes. records, will often reveal such pi oblems as scour tendencies, shifts in the channel, and deg: 5-26.3 Illustrations of Waterway Problems. radation. The following illustrations show some of the (2) Soundings. Soundings for scour should more common waterway problems.

5-87 Channel Change Crossing

Meandering 5freain

Figure 5-106.Channel change. The channel change steepens the channel profile and increases flow velocity. The entire section may degrade.

New Dam

IC TO.S.S;/7q EMI

CIEl

Figure 5-107.Sediment deposits. Sediment previously carried downstream is deposited in the reservoir, which acts as a settling basin. The increased scour capability of the downstream flow may degrade the lower channel.

5-88 Diredion of High ,Woier

low 1/Vaier Channel

Figure 5-108.Pier scour. Scour around piers is influenced greatly by the shape of pier and skew to flood flow. Note direction of flood flow is different from that of normal channel flow.

5-89 ====1. Crossing Rfrop Around Piers

>Down Sireom Scour Hales Lined Channel

/1'.. A\

Figure 5-109.Loose riprap. Loose rock riprap piled Figure 5-110.Lined banks tend to reducel scour, but around piers to prevent local scour at the pier may such a constriction might increase general scour in the cause deep scour holes to form downstream, bridge opening, especially at an adjacent or end pier.

tb lf

Pier

0 00

fin. in II\ I / \ f \

Figure 5-111.Scour reduction. Scour at the pier may be reduced significantly by placing piles upstream in a wedge shaped .pattern as shown.

5-90 d Flood Plain Former Low Jf Wafer Channel

New low Alder // Channel Affair /if Flood Crossing

Figure 5-112.Channel change. New low water channel is formed during flood at the river bend.

'Pond Afier flood

Figure 5-113.Horizontal or vertical channel constrictions. A firm or riprapped bottom or a horizontal constriction can cause a deep scour hole downstream with severe bank eroeion resulting in downstream ponding as shownin the sketch.

5-91 Former MeanderingSfream Channel--

Crossing

Figure 5-115. New channel. New channel cuts of ox- bow and changes the river profile. The upstream reach may degrade.

Borrow Area Increased Flow VQ /ocifq

Crossing

Figure 5-116.Gravel removal leading to upstream degradation. Removing large quantities of gravel from river bottom causes degradation upstream.

flood Plain Approach Embank nenl c74.7,7e/ Figure 5-114.Scour reduction. Wide footings or rock aprons beneath the bed level tend to reduce scour by deflecting downward currents. A projecting foundation on the other hand will tend to increase depth of SCOW'. Figure 5-117.Scouring during flood. During flood the waterway constriction may produce general scouring in the vicinity of the bridge.

5-92 Section 27. BOX CULVERTS

5-27.1 General. Box culverts range in size from small single cell units to multi-cell units as large as 20' x 20'. While natural rock, when present, may be used as a floor, the box culvert (fig. 5-120) is usually a closed, rectangular frame. Usually, transverse joints are provided every 20' to 30'. Occasion- ally, old culverts consist simply of a slab on a wall. These are not true box culverts. Some of these slabs are made of stone, while some walls are made of rubble masonry, rather than concrete.

1" 5-27.2 Types of Culvert Distress. A culvert is generally used where its construc- Deepest Scour tion would permit a fillto substitute for a Will Probably bridge without any loss of vital waterway area. Occur Here This combination of high earth loads, long pipe-like structures, and running water tends to Figure 5-118.Scour due to protruding abutments. produce the following types of distress : Protruding abutments may produce local scour. Deepest scour usually takes place at the upstream corner. The a. The basic causes and actions of foundation severity of scour increases with increased constriction. movements are discussed in Section 5-7. Here, they need only be listed. (1) Settlement of the box. This may be either a smooth sag, or it may be differential settlement at the expansion joints. (2) Tipping of wing walls. (3) Lateral movements of sections of the box. kft b. High embankments may impose very heavy loads on the top and bottom slabs. These earth pressures can cause either shear or flexural failures in the top slabs. c. Construction defects can lead to structural distress. Debris d. Undermining is a form of scour attack on the upstream and downstream ends of box culverts. When sheeting, or a concrete cut-off wall, is either not provided or is not deep enough, the stream may wash away the soil under the ends yr /It --- /4It //t /A of the floor slab, the apron, or the wing wall footings, leading to settlements and culvert cracking. e. Plugging may result from debris collecting Figure 5-119.Scour due to debris. Collection of de- over the mouth of the culvert. This can cause bris around piers, in effect, enlarges the size of the flooding (fig. 5-121) and flotation and displace- pier and causes increased area and depth of scour. ment of part, or all, of the box.

5-93 -11 .:. A Ffflinik7 Mr:3(4214,,i;t1 ;171, Maignakirl Magrari! rigie:04.1 OWEISIONSWIAMOMP !P° Ert

1-^ Figure 5-120.Two-barrel box culvert.

f. Water leaving the box at high velocities h. Check for cracks and spalls in the top slab. may cause downstream scour at the stream bed. Longitudinal cracks indicate either shear or flexure problems; transverse cracks indicate 5-27.3 What to Look for During Inspection. differential settlement. Cracks in the sides may be from settlement or from extremely high a. Check for sag of the culvert floor. In times earth pressures. Note the size, length, and loca- of light flow, this may be noted by location of tion of the crack. Look for exposed or rusty sediment. Where there are several feet of water rebars. in the box, a profile of the crown may be taken. i. Where there is no bottom slab, look for un- b. Check for sag in the profile of the road- dermining of side footings. way overhead. j. Check for undermining at the ends of the c. Check for vertical differential settlement at box and under the wings, the expansion joints. d. Check for transverse and longitudinal dif- k. Examine the inside of the box for large ferential settlements at the expansion joints. cracks and debris. This may indicate the need for a debris rack. Check the inlet end of the e. Check for widely opened expansion joints. culvert for debris. Note whether vegetation ia Water may be seeping through joints from soil obstructing the ends of the culvert. outside. 1. If the culvert floor is visible, check it for f. Check for canted wingwalls. This condition may be due to settlement, slides, or scour. abrasion and wear. g. Check for slide failures in the fill around rn. Note any other signs of deterioration of the box. Such slides are likely to affect the box the concrete box, especia 'y those which suggest as well. design error or construction omissions.

5-94 I CULVERT I

jr f , 1,, -':,., ''' ...... , ".."11(.21itirrr..4ACIN,P.)AX.., Is. "'...".,r.'. 4.; : Atifr . : '.,,,1,., r. r4.-,. ., , ,...,,,,.....f A.., ,-....- ....,..14,..' it AOr , 414 71..4 1....., . 9 ... Agr.....10, .X,r,,.,Pr '. .. .,--.,...,.ear . S Jr, ..... -~ ,, qv* ,.....stpw; - . ' .... ,....--,:r .....- -`',.. ..,.. ------01001101F...... 1qr,:. "*."'" ,...I 40,..,1.--.; %... / - . 'N.A., 41 s" -, ' - .... ,,,A. 4...,Mrebrt.4". ,,, *1 " . s 1110:r- ,', .. : ,....1100°. 1 ,. . 7,*+11 s,' °- 144: Jr. e.'At "*.i;,. jr...at-TT nop. -) trf

Figure 5-121.Roadway washed out by flood. Note that culvert is still intact.

Section 28.PAINT irreparable damage to the bridge. The life of many bridges has been significanily reduced be- 5-28.1 General. cause of neglected painting. The amount of Since painting is the primary means for pro- paint maintenance required is influenced by the tecting structural steel against rust and corro- environment. In damp coastal regions, or in sion, it is imperative that the condition of the. urban industrial areas, a program of annual paint applied to the structural steel elements of spot painting may be necessary, and complete repainting of the bridge structure may be re- the bridge be thoroughly inspected and fully required as often as every four or five years. In ported upon. Continual exposure to the effects dry climates, repainting may not take place for of weathering and chemical action requires that as long as 10 years and, in some cases, the inter- paint be continually maintained. Spot failures val between painting may approach 15 years. can develop rapidly into large areas of corro- Other factors affecting the life of the paint are sion which, if permitted to continue over a pe- type, quality of its application, structural de- riod of time, can cause extensive and, possibly, tails, and the amount of exposed areas.

5-95 5-28.2 What to Look fel. During Inspection. with a "Low Clearance" sign (fig.5-123and a. Examine all paint carefully for cracking or 5-124). chipping, scaling, rust pimples, and chalking. (3)Lateral Clearance. Many new bridges Look for evidence of "alligatoring." If the paint are narrower than they should be. "Narrow film has disintegrated, note whether the prime Bridge" signg and striped paddleboards (fig. coat or the surface of the metal is exposed. Note 5-124),should be used when the bridge width is the extent and severity of the paint deteriora- legs than that of the approach roadway. If the tion. If extensive "spot" painting will be re- superstructure or parapet end extends above quired, probably the entire structure should be the curb, it should be striped and a reflectorized repainted; otherwise, "spot" painting will most hazard marker should be attached. likely be sufficient. (4) Narrow Underpasses. Where the road- b. Look for paint failure on upper chord hori- way narrows at an underpass, or where there is zontal, surfaces, or those _surfaces which are a pier in the middle of the roadway, striped most exposed to sunlight or moisture. Give par- hazard markings should be placed on the abut- ticular attention to areas around rivets and ment walls and on pier edges. Reflective hazard bolts, the ends of beams, the seams of built-up markers should also be placed on the piers and members, the unwelded ends of stiffeners, and abutmenfs, and theapproaching pavement any other areas that are difficult to paint or should b.- appropriately marked to warn the ap- that may retain moisture. proaching traffic of the hazard. (5)Speed and Traffic Markers. These types of signs should be checked to ascertain Section 29.SIGNING whether they are appropriate. Speed restrictions should be carefully noted to determine 5-29.1 General. whether such restrictions are consistent with This section is concerned with the presence and bridge and traffic conditions. Additional traffic effectiveness of bridge signing. Both the signs markers may be required to facilitate the safe and the sign support structures should be in- and continuous flow of traffic. spected. (6) Movable Bridges. Signs warning of draw spans (fig. 5-123) and submarine cables, 5-29.2 What to Look for During Inspection. should be posted.. Interconnected traffic signals a. Type of Signs. When inspecting a bridge and drawbridge gates should also be provided. for signing, note not only the signs thatare (SeeSection5-32dealingwithmovable posted, but whether additional signs are needed bridges.) because of changed bridge or roadway condi- b. Locations of Signs. The warning signs tions. The types of warning and regulatory should be located sufficiently in advance of the signs that are normally required are: structure to permit the driver and his vehicle to (1) Weight Limit. This is the most impor- react. The weight limit sign, being regulatory, tant inspection item particularly for the older should be located just ahead of the bridge. Lat- bridges (fig.5-122). Ifthe bridge structure was eral clearance of the sign should be determined designed and constructed prior to 1940,capac- by the requirements of the highway type. On ity of the bridge may be a problem. freeways, side-mounted signs should be : (2)Vertical Clearance. While most newer (1) Positioned 30 feet from the edge of the bridges have adequate vertical clearances, older travel way, bridges are often substandard in this respect. (2) Located behind a barrier, guardrail, or Where nolimiting verticalclearancesare (3) Affixed to a breakaway installation. On posted for old through-truss bridges, railroad other highways, signs should preferably be lo- underpasses, or old grade separations, measure cated behind .a barrierguardrail or be affixed to the clearances to determine whether they meet a breakaway standard. Any sign support of suf- the established legal minimum standard. Any ficient mass to be a hazard, which does not meet clearance that is less than 1 foot higher than the preceding criteria, should be noted and re- the legal height and load limit should be posted ported.

5-96 c. Condition. It is important that all caution area. It is suggested that the Manual on Uni- signs be in good condition. Evaluation of the form Traffic Control Devices (MUTCD) be con- condition and adequacy of the signing will de- sulted for specific information with regard to pend upon the conditions prevailing in a given signing. Signs should be checked for : OBEY POSTED SIGNS!

A LOAD UM SIGN MEANS JUST THAT!

As.

Olmstead Bridge RobertsvilleRoad Division Street Southbury Aug 9,1967 Colebrook Oct 19, 1967 Berlin Dec 7,1967 Waterbury Republican Hartford Courant Middletown Press Photo by George Krimsky Photo by Joseph O'Brien Photo by Ken Skinner

YOU'D BETTER BELIEVE IT: THESE TRUCK DRIVERS DIDN'T!! Figure 5-122.Safety poster illustrating the danger of ignoring load limit signs.

5-97 (1) Reflectorization. Adequate reflectoriza- at least 30" x 30". "Low Clearance" signsare tion and/or painting are required for night vis- 36" x 36". The "Weight Limit" signsare rec- ibility. tangular with minimum dimensions of 18"x (2) Legibility. Note whether the legend is 24". difficult to read. This may be because of dirt encrustment, dulled paint, inadequate lettering, (5)Vegetation. On minor roads, heavy or inadequate sign size. Refer to the Manual on vegetation growth may obscure signs. Note the Uniform Traffic Control Devices for Streets type and location of such vegetation so that it and Highways for guidelines as to criteria to be may be trimmed or removed entirely. If reloca- followed in evaluating sign legibility. tion of the sign(s) is necessary, include such (3) Vandalism. Bullet holes, paint smears, remarks in the inspection report. campaign stickers, etc. should be noted. (6) Sign Support Damage. Note whether (4)Minimum, Sizes.Ingeneral, most sign supports are bent, twisted, or otherwise warning signs are diamond-shaped and measure damaged.

5-98 Figure 5-124.Approach to narrow bridge. Note paddle boards and striping of endposts and portal chord,

Section 30. UTILITIES prises, e.g., gas, light and telephone companies, will usually perform the scheduled maintenance 5-30.1 General. of their facilities, some of the smaller publicly owned utilities, e.g., water companies, are less a. It is common for commercial and industrial likely to perform adequate maintenance since utilities to use highway rights-of-way and/or they may not be as well staffed. Most utility adjacent areas in order to provide goods and lines or pipes are suspended from bridges be- services to the public. To bridge engineers, this tween the beams or behind the fasciae. On older means that some utility operationswill be bridges, water pipes and sewer .pipes may be found on a numbof bridge structures (fig. installed along he sides of the bridge or may be 5-125). These ciierations may be one or more of suspended under the bridge. the following : gas, electricity, water, telephone, sewage, and liquid fuels. 5-30.2 What to Look for During Inspection. b. Utility companies perform most of their facilities installation and most of the required a. Check pipe, ducts, etc., for leaks, breaks, maintenance. While the large commercial enter- cracks, and deteriorating coverings. 5-99 bay, report this condition for either auxiliary encasement or future relocation. g. Check utilities that are located beneath the bridge for adequate roadway clearances. h. Determine whether any utility obstructs the waterway area or are positioned so that they may hinder drift removal during periods of high water. i.Check the encasement of pipes carrying fluids under pressure for damage, and check vents or drains for leaks. j. Check for the presence of shut-off valves on pipelines carrying hazardous pressurized fluids, unless the fluid supply is controlled by automatic devices. k. Note whether any utility is located where there is a possibility that it may be struck and damaged by traffic or by ice and debris carried by high water. 1. Determine whether utilities are adequately supported and whether they present a hazard to any traffic which may use or pass under the bridge. m. Check for wear or deteriorated shielding and insulation on power cables. now n. Check for any adverse effect utilities may Figure 5-125.Utility installations on bridge. have on the bridge,e.g.,interference with bridge maintenance operations or an impairing of structural integrity. b. Check the supports for signs of corrosion, o. Check to determine whether vibration or damage, loose connections, and general lack of expansioh movements are causing cracking in rigidity. If utility mounts rattle during passage the support members. of traffic, especially on steel bridges, note need p. Check supporting members of the bridge for padding. for paint damage. c. Check the annular space between pipe and q. Note any adverse aesthetic effect utilities sleeve, or between the pipe and the blocked up may have on the bridge. area for leaks where utilities pass through abutments. Section 31. LIGHTING d. Check for leaky water or sewer pipes located above the decks or on top of beams. Leak- 5-31.1 General. age from these pipes can cause serious corrosion of the deck or beams. Lighting on bridges will consist of "whiteway" lighting, sign lights, traffic control lights, navi- e. Inspect the area under water or sewer gation lights (fig. 5-126), and aerial obstruc- pipes for damage. tion lights. The last two types of lights are spe- f.Determine whether mutually hazardous cial categories which are encountered only on transmittants, such as volatile fuels and elec- bridges over navigable waterways or on bridges tricity, are sufficiently isolated from each other. having high towers. There will, of course, be If such utilities are side-by-side or in the same many bridges with no lighting at all.

5-100 J

Figure 5-126.Navigation light on pier. 5-31.2 Highway Lighting. ments for the type, number, and placement-of Conventional highway lighting on bridges pre- navigation lights on bridges. It should be noted sentsrelativelyfew problems.The most that Coast Guard District Commanders have common problems are discussed below. the authority to waive requirements for naviga- a. Collisions. Most light standards on the tion lights on bridges. more modern bridges are supported on parapets, or are located outside the rails. However, 5-31.4 Aerial Obstruction Lights. on some older urban bridges, light standards These lights are required on all bridges project- may be unprotected and, consequently, they are ing far enough above ground to be a possible more vulnerable to damage or destruction from hazard to aircraft. If the tops of the bridgesare vehicles. not much higher than the surrounding build- b. Vandalism and Burnouts. Generally, dam- ings or trees, obstruction lightsare probably aged lighting elements and dead bulbsare re- unnecessary. The requirements for aerial ob placed routinely by maintenance forces. Never- struction lights may be waived at the discretion theless, such items should be noted and reported of the Federal Aviation Administration -Re- by bridge inspectors. gional Director.

5-31.3 Navigation Lights. 5-31.5 What to Look for During Inspection. Coast Guard Publication 208 lists the require- a. Whiteway Lighting.

5-101 IWI1hilimmindlid hiliss

-- CHANNEL I

SINGLE-SPAN FIXED BRIDGE

AILAMAL

_MAIN_CHANNEL__421T --CHANNEL CHr NNEL_-- H B 4 ALSO 3 WHITE LIGHTS IN VERTICAL LINE (D)

B A

MULTIPLE -SPAN FIXED BRIDGE

LIGHT COLORS AND HORIZONTAL ARCS OF VISIBILITY

CHANNEL CENTER-360° GREEN (180° GREEN C PIERI80' 3ED. ON BRIDGES LIGHTED PRIOR TO JAN. 1,1947, UNTIL LIGHTS ARE REPAIRED OR REPLACED),

MAIN CHANNEL-180' WHITE, 3 LIGHTS IN VERTICAL LINE (60°-180° ON BRIDGES LIGHTED B CHANNEL MARGIN-180° RED. D PRIOR TO JAN. 1,1953, UNTIL LIGHTS ARE REPAIRED OR REPLACED).

Figure 5-127.Minimum lighting requirements for fixed bridges.

5-102 CLOSE'?

PROTECTION PIER

DRAW PIVOT PIER I PIER

Axis -

THROUGH BRIDGE

B B

PROTECTION PIER

DRAW PIVOT , PIER PIER

DECK BRIDGE

LIGHT COLORS AND HORIZONTAL ARCS OF VISIBILITY

SWING SPANALTERNATE RED (2) AND A0GREEN (2), EACH 60 AND AT 90° TO EACH ,PIERI80° RED. OTHER.

COSWING SPANALTERNATE RED( I) AND AXISI80° RED. B GREEN (2), EACH 60° AND AT 90° BETWEEN D MAY BE OMITTED WHEN DRAW AND PROTEC. RED AND GREEN. TION PIERS ARE STRAIGHT ON THEIR CHANNEL FACES.

Figure 5-128. Minimum lighting requirements for double-opening suing bridges.

5-103 15' 1 I I BL

ABUTMENT DRAW SPAN ABUTMENT CLOSED OPEN

PONTOON BRIDGE

DRAW SPAN CLOED

I 1 I LJ A LJ LJ I_J ..01 0

FOLDING BRIDGE

15' 11:226P00.7A

OPEN

11111=11

LIGHT COLORS AND HORIZONTAL ARCS OF VISIBILITY

DRAW SPANALTERNATE RED 2) AND GREEN B (?), EACH 60° AND AT 90° TO EACH OTHER. alit PIER OR ABUTMENTI80° RED.

Figure 5-129.. Minimum lighting requirements for single-opening drawbridges..

5-104 DOUBLE-LIFT BRIDGE

LIFT SPANS ..-----

CLOSED CLOSED A

PROTECTION PIERS A A

CLGSED- BRIDGE-AXIS-

A A DRAW PIERS 0 LIGHT COLORS AND ARCS OF VISIBILII

LIFT SPAN-180° GREEN WHEN LIFT SINGLE.LIFT BRIDGE SPAN IS FULLY OPEN FOR NAVIGATION, 160° RED FOR ALL OTHER POSITIONS OF LIFT SPAN (60- OR LESS GREEN AND RED PERMITTED ON BRIDGES LIGHTED PRIOR TO JAN. 1, 1949, UNTIL LIGHTS ARE LIFT SPAN REPAIRED OR REPLACED).

PIER- I BO° RED.

AXIS-I80° RED. MAY BE OMITTED WHEN DRAW AND PROTEC- BRIDGE AXIS TION PIERS ARE STRAIGHT ON THEIR CHANNEL FACES. DRAW PIERS

Figure 5 -180. Minimum lighting requirements for bascule bridges.

5-105 PROTECTION PIERS ible, A

LIGHT COLORS AND HORIZONTAL ARCS OF VISIBILITY

e PIER-180° RED LIFT SPAN -360° GREEN WHEN LIFT SPAN FULLY OPEN FOR NAVIGATION, 1800 RED FOR ALL OTHER POSITIONS OF LIFT SPAN (180° GREEN AND RED PERMITTED ON BRIDGES LIGHTED PRIOR TO JAN. 1, 1949, UNTIL LIGHTS ARE REPAIRED OR AXISI80° RED. MAY BE OMITTED WHEN LIFT AND .PROTEC- REPLACED). C TION PIERS ARE STRAIGHT ON THEIR CHANNEL FACES. 1 . Figure 5-131. Minimum lighting requirements for vertical lift bridges.

5-106 (1) Collision. Note any light poles that are e. Navigation Lights. dented, scraped, cracked, inclined, or otherwise (1) Lights. Check to determine 'whether all damaged. of the required navigation lights are present (2) Fatigue. Aluminum light standards and properly located. For fixed bridges, a green and castings are most likely to suffer from fa- navigation light is suspended from thesuper- tigue. Check for cracking in : structure over the channel centerline and red (a) Mast arms and cast fittingson lights are placed so as to mark the channel standards. edges. When piers are situated at the channel (b) At the base of standards, especially edges, the red lights are positioned on the piers the cast elements. or fenders (fig. 5-127). For movable spans, (3) Corrosion. Check steel standards for navigation lighting requirements vary accord- rusting, and concrete standards :for cracking ing to the bridge type. When in doubt as to the and spalling. requirements refer to Section 68 of the Coast Guard pamphlet CG204, "Aids to Navigation." . b. Electrical Systems. This part of the inspec-,-However, figures 5-128, 5-129, 5-130, and tion should be made by or with the assistance of 5-131 illustrate present requirements. a qualified electrician. (2) Lighting Devices. Check the overall (1) Wiring. Observe any ex,osed wiring conditionoflightingdevicestodetermine for signs of faulty, worn, or flaiviaged insula- whether they are rusted, whether any of the tions. Note and report the following: lenses are broken or missing, and whether the (a) Bad wiring practices. lights are functioning correctly. (b) Bunches of excess wires. (3) Wiring. Check the condition of wiring, (c) Loose wires. conduits, and securing devices to determine (d) Poor wire splices. whether they are loose or corroded. (e) Inadequate securing of ground lines. f.Aerial Obstruction Lights.For short (2) Junction Boxes. Check inside junction bridges (less than 150'), these should be at least boxes for excessive moisture, drain hole, poor two continuous glow red lights mounted at the wire splices,and loose connections. Note the high points of the superstructure. For longer condition of wiring and insulation. Where the structures, the red lights should be placed at base of the light standards contains a junction 150 to 600 feet intervals, while sets of at least box, examine this as well. Note whether the three flashing red beacons should be mounted junction 'box, outlet box, or switch box covers atop the peaks of widely separated high points are in place. such as suspension bri3ge towers, truss cusps, etc. Check these lights for proper maintenance (3) Conduit. Check conduits for rust or and functioning. missing sections. Check the curbs and sidewalks for large cracks that might have fractured the conduit imbedded in them. Note whether the Section 32.MOVABLE BRIDGES conduit braces and boxes are properly secured. (4) Whiteway Current. On those struc- 5-32.1 General. tures where the whiteway current is carried Movable bridges are normally constructed only over an open line above the sidewalks, check for when fixed bridges are impractical or when hanging objects such as fishing lines and moss. such construction would be inordinately expen- c. Lamps or Damaged Standards. Note any sive. Three categories of movable bridges com- priseover ninety-five percent ofthetotal missing lamps or damaged standards. A cover number of movable bridges within the United placed over the electric eye controller, will turn States. These categories are: on the lights. Note the number and the locations of those lights that do not illuminate. a. Swing Bridges. These bridges consist of two-span trusses or girders which rotate hori- d. Sign Lighting. Inspect sign lighting for the zontally (fig. 5-132). The spans are usually, but same defects as conventional lighting. not necessarily, equal. When open, the swing

5-107 Figure 5-132.Swing bridge. spans are cantilevered from the pivot (center) (2) Rim-Bearing. This type of swing span pier ; when closed, the spans are supported at transmits all loads to the pivot pier, both dead the pivot pier and at two rest (outer) piers or and live, through a circular girder or drum to abutments. In the closed condition, wedges are bevelled rollers. The rollers move on a circular usually driven under the outer ends of the track situated inside the periphery of the pier. bridge to lift them (fig. 5-133), thereby provid- The rollers are aligned and spaced on the track ing a positive reaction sufficient to offset any by concentric spacer rings. This type of swing possible negative reaction from live load and span bridge also has a central pivot bearing impact. This design feature prevents uplift and which carries part of the load and is connected hammering of the bridge ends under live lOad to the rollers by radial roller shafts. conditions. Swing spans are subdivided into : On both types of swing bridges, the motive (1) Center-Bearing.This type of swing power is usually supplied by an electric motor, span carries the entire load of the bridge on a although gasoline engines or manual power may central pivot(usually metal discs): Balance also be used. The bridge is rotated by a circular wheels are placed on a circular track around the rack and pinion arrangement. outer edges of the pivot pier to prevent tipping (fig. 5-134). When the span is closed, wedges b. Bascule Bridges. In this type of bridge the similar to those at the rest 'piers are driven leaf (movable portion of the decks) lifts up by under each truss or girder at the center pier. rotating vertically about a horizontal trunnion This relieves the center bearing from carrying (axle)(figs. 5-135, 5-136, and 5-137). This any live load. However, these._wedges do not trunnion is positioned at the dead load centroid. raise the span at the pivot pier, but are merely Bascule bridges may be either single or double- driven tight. leafed. In the former case, the entire span lifts

5-108 LIVE LOAD SUPPORTWEDGE Afe,

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Figure 5-133.Outer end of swing bridge on rest pier. about one end (fig. 5-136). A double-leafed bas- (2) Rolling Lift (Scherzer) Bridge. This is cule has a center joint, and half of the span a bascule bridge type whose Complete super- rotates about each end (figs. 2-18 and 5-137). structure, forward leaf or span itself, rear arm, It is obvious that a counterweight is necessary and counterweight rolls back from the channel. to hold the raised leaf in position. In older This is accomplished with a quadrant or seg- bridges, the counterweight is overhead, while in mental girder whose center of rotation is at the the more modern bridge, the counterweight is centroid of the bascule. The girder rims roll often placed below deck and lowers into a pit as along a toothed track and in so doing lift and the bridge is opened. When the bridge is closed, withdraw the leaf. A horizontal retraction of a a forward bearing support located in front of cable or rack attached to the centroid of the the trunnion is engaged and takes the live load bascule leaf produces this motion. reaction. On double -leaf bascule bridges, a tail- (3) Rall Lift. This is a variation of the lock behind the trunnion and a shear lock at the rolling lift bascule bridge in which the segmen- junction of the two leaves are also engaged to tal girder is replaced by a large roller at the stiffen the deck. There are several varieties of bascule's centroid. To open the bridge, the roller bascule bridges, but the most common are: moves backward on a horizontal track. (1) Chicago (or simple) Trunnion. This (4) Heel Trunnions (Strauss). This class variety of bascule bridge consists of a forward f)f bascule bridge employs four trunnions con- leaf and a rear counterweight arm which ro- necting the sides of a parallelogram-shaped tates about the trunnion. The trunnion bearings, panel formed by the lift span and a fixed trian- in turn, are supported on the fixed portion of gular rear panel. The principal trunnion about the bridge such as a trunnion girder, steel col- which the movable span rotates is at the heel of umns or on the pier itself. the truss. Figure 5-138 illustrates the action 5-109 e: .x.0311 =,s ,, y ,

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L." L:ti:,;5:;447:4 "7-i. " Figure 5 -134.Balance wheels and rack on. center bearing awing span. which takes place when the movable span ro- movable bridges, too. Therefore, most of the tates. bridge structure dofects and deterioration listed All of these lvidges are powered by electric elsewhere as potential problems -apply to mova- motors with a rack and a pinion attachment. ble spans also. c. Vertical Lift Bridges. These bridges have a b. Mechanical and electrical equipment in- movable span with a fixed tower or towers at cludes specialized areas which are beyond the each end. The span is lifted by cables at its four scope of this manual. Since operating equip- corners. The cables pass over sheaves (pulleys) ment is the heart of the movable bridge, it is atop the towers and connect to counterweights recommended that expert assistance be ob- on the other side. The counterweights descend tained '-then conducting an inspection of mova- as the span ascends. The actual lifting of the ble spans. It should be noted that in many cases, cables is performed through the turning of the owners of these movable bridges follow ex- drums which wind the lifting cables as they si- cellent programs of inspection, maintenance, multaneouslyunwindthecounterweighted and repair. cables. While a number of vertical lift bridge variations can be listed, they all operate basi- c. Fatigue can be a problem with movable cally in the same manner as that described bridges due to the reversal or the fluctuation of above. stress as the span opens and closes. Any member or connection subject to such stress varia- 5-32.2 Types of Distress Encountered in Mova- tions should be carefully inspected for fatigue ble Bridges. failure. a. Defects, damages, and deterioration typical d. Swing bridges are probably most suscepti- of all steel and concrete structures can strike ble to the following deficiencies :

5-110 =

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Figure 5 -136.Trunnion bascule bridge.

5-111 Twin leaf bascule. Figure 5-1574 , \ -7

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Figure 5-139.Rolling-lift bascule bridge. (1) Structural fatigue. ing Lift Bridges. Figure 5-139 illustrates a roll- (2) Maladjustment of the outer bearings ing lift bascule bridge. These bridge features and of the live load bearings at the pivot pier frequently cause maintenance problems. The re- (on center bearing swings). This could cause peated pressure exerted between the rolling gir- uplift at one end, of the swing span, hammering ders and the tracks will cold work the girder or of the bridge upon the rest piers, awl excessive the track, causing an extension of one of the strain or wear upon the centek-beariri, .s. plates. Where a toothed track is used, rolling (3) Wear of the discs in the center bear- will be hampered. Where smooth plates are ing. used, the segmental girder may lengthen, caus- (4) Distortion of the rim bearings on the ing binding at the rear joint. Sometimes the pivot pier. The outside rollers may crowd in- track may flatten, warping the member to ward or outward, developing horizontal forces which it is connected and causing fatigue crack- on the center pivot. This may result in loosening. ing of the pivot or in destructh:e wear. (3)Front Load Bearings. When these (5) Worn and -Maladjusted span locks on bearings are out of adjustment live load forces the rest piers. can shift to the main trunnion causing over- e. Bascule Bridges. stress and increased wear. (1) Center Lock. This device is designed to (4) Bascule Main Leaf Girders. Since it is transmit shear at mid-span between the two not possible to describe all types of bascules, it leaves of a double-leaf bascule, and is usually should be noted that many of these bridge types some form of an interlocking key and slot ar- trar -ler the full reaction from the trunnion rangement. Although some bridges lock by a bearings to the substructure by means of large simPleMeshing process, most are likely to em- girders, floor beams, or heavy bracings. In such ploy a movable piston. Should the tongue or slot cases, the members that are exposed to these become worn, the increased play in the lock will stresses should be inspected carefully for signs allow vibration and deflection. of distress or corrosion. (2) Segmental Girder and Track on Roll- (5) Trunnions. A trunnion and its bear-

5-113 ings constitute the focal point of the leaf's rota- (4) Piers.Check the piers for rocking tion and as such are subject to deflection and when the leaf is lifted. This is an indicator of wear, either of which can impair the opera- a possible serious deficiency and should be re- tional efficiency and/or safety of the bridge. ported at once. f. Vertical Lift Bridges. Check the condition (5) Warning Devices. of the cables and determine whether they have (a) Check the operation of safety gates. freedom of movement. barriers, and warning signals. Be sure they function properly and that the warning signals 5-32.3 What to Look for During Inspection. give sufficient notice to permit vehicles to clear a. General. the automatic gates. (1) Cables. Counterweight cables as well (b) Determine whether manually oper- as uphaul and downhau] cables on lift or bas- ated ;safety gates should be converted to me- cule spans should be inspected carefully for chanically operated gates. wear, damage, corrosion, and evidences of inad- (c) Determine whether the safety gates equate lubrication. To properly inspect cables, and barriers are sound and well maintained. old lubricant must be removed. After inspec- Note any decayed areas atbolt and other tion, the cable should be relubricated. Check for connections. Note whether either needs to be any binding at the travel rollers and guides. replaced or repaired. Check the piers for rocking when the leaf span (d) Note the locations of the safety is lifted. gates in relation to the warning light signs and (2) Counterweights and Attachments. bells, and the bridge opening itself. Check the (a) Check the counterweights to deter- warning lights with regard to location to determine if they are sound and are properly affixed mine whether they can be easily seen by motor- to the structure. Further check temporary sup- ists. ports for the counterweights that are used dur- (6) Aids to navigation. Lights and fenders ing bridge repair. are very important, and should be inspected as (b) Where steel members pass through, discussed in Sections 25 and 31 of this chapter. or are embedded in the concrete, check for any Clearance gauges shall be inspected for visibil- corrosion of the steel member and for rust ity and legibility. stains on the concrete. (7) Trunnion girders. Examine all main (c) Look for cracks and spalls in the trunnion girders and floor beams for buckling concrete. or cracking due to overstress or fatigue. (d)Check for debris,animals, and (8) Trunnions and bearings. These should insect nests in the counterweight blocks. be checked for weakness, excessive play, corro- -(e) Where cable counterweights (bal- sion, and undesirable deflection or bending. ance chains) are employed, check links, slides, (9) Machinery. On all movable structures housings, and storage areas for deterioration, the machinery is so important that considerable for adequacy of lubrication, where applicable, time should be devoted to its inspection. The and for protection. items covered and termed as machinery include (f) Determine whether the bridge is bal- all motors, gears, tracks, shafts, linkages, ov- anced and whether extra weight blocks are erspeed control, brakes, and any other integral available. A variation in the power demands on part that transmits the necessary power to op- the motor, according to the span's position, is erate the movable portion of the bridge. The an indicator. inspection of the next ten items and items simi- (g) Paint must be periodically removed lar to them should be made by a machinery or from the lift span proper; otherwise, the coun- movable bridge specialist. terweights will eventually be inadequate. (a) Check the alignment of all gears, (3) Drainage. Check to determine whether locks, and other interlocking mechanisms. the counterweight is properly drained. On verti- (b) Check the adequacy of the lubrica- Cal lift bridges be sure that the sheaves and tion of all movable parts, particularly where their supports are well drained. Examine any meshing or contact occurs between the movable portion of the bridge where water can collect. parts. Also check the schedule of lubrication to

5-114 determine whether the frequency of lubrication Trial openings should be specifically for inspec- is sufficient. tion. During the trial openings, the safety of (c) On live load bearings, check the the inspection personnel should be kept in mind. wedge (lock) linkages for loose knee pins and for excessive play. Note the closing and the re- b, Swing Bridges. leasing of the wedge locks or pin locks for (1) Check the wedges and the outer bear- proper functioning. ings at the rest piers for maladjustment. This (d) Check all gears for cracks including can be recognized by excessive vibration of span the teeth, spokes, and the hub. or uplift when load comes upon the other span. (e)Inspectallshaftsfortwisting, (2) Check the live load wedges and bear- strain, and for play within bearings. ings located under the trusses or girders at the (f) Check the keyways on the shafts and pivot pier for proper fit. the gears for looseness. Check the keys for (3) Check the teeth of all gears for wear looseness also. and for proper alignment. The meshing ofgef..i.s (g) Check the braces, bearings, and all should be checked so as to determine whether the housings for cracks especially where welded gears are climbing one upon the other. joints occur. (4) On center- bearing swings, check the (h) Inspect the concrete for cracks in center pivot, the housing, the tracks, and bal- areas where machinery bearing plates or braces ance wheels for fit, wear, pitting, and cracking. are attached. Note the tightness of bolts and the Check for proper, and adequate lubrication. tightness of other fastening devices used. (5) On rim bearing bridges inspect the (I) Check all brake devices for proper center pivots, the rollers and the roller shafts, functioning. and the guide rings or tracks for proper fit, (j) Check to see whether stops are used wear, pitting, and cracking. Check for proper or needed. and adequate lubrication. (10) Motors and Engines. The inspection of motors and engines should be made by me- c. Bascule Bridges. chanical specialists. The inspection should in- (1) Check the center locks on double-leafed clude the check of the following conditions: spans, and note whether there is excessive de- (a) If a belt drive is used, check for flection of the center joint or vibration on the wear and slippage. Note the condition of all bridge. Inspect the locks for fit and for move- belts and the need for replacement, if any. ment of the leaf (or leaves). Check lubrication (b) If a friction drive is used, check for and loose bolts. Check the lock housing and its wear and for uneven bearing areas. braces for noticeable movement. This can be (c) If a direct drive is used, check all done by observing the paint adjacent to it for bracings and bearings for tightness. signs of paint loss or wear. (d) If a liquid coupling is used, check the (2) Check the differential vertical move- fluid to ascertain that the proper quantity is ment at the joint between the two leaves under used. Look for leaks. the passage of heavy loads. (e) In movable bridges, check the flexi- . (3) Check the joint between the two leaves ble cable to the motor. for adequate clearance. (11) Grid Decks. (4) Check the front live load bearings to (a) Check structural welds for sound- determine whether they fit snugly. Also observe ness and the grid de °ks for skid resistance. the fit of tail-locks at rear arm and of support (b) Check rw; away surface for evenness at outer end of single leafers. of grade and for adequate clearance at the (5) Check the bumper blocks' and the at- joints where the movable span. meets the fixed taching bolts for cracks at the concrete bases. span. (6)Check the counterweight well for (12) Conduct trial openings as necessary excess water. Check the condition of the sump *to insure proper operational functioning and pump, the concrete for cracks, and the entire that the movable span is properly balanced. area for debris.

5-115 (7) Check the brakes, limit switches, and (2) Check motor mounting brackets to en- stops (cylinders and others) for excessive wear sure secure mounting. and slip movement. Note whether.the cushion (3) Check alignment and wear of cables, cylinder ram sticks oro inserts too easily. drums, and sheaves. Note whether cable is run- (8) Check the shaft or trunnion bearings ning properly in sheave grooves. Recommend for excessive wear, lateral slip, and loose bolts. the replacement of all frayed or worn cables. (9) Check shear locks for wear. Excessive Look for any obstructions to proper movement movement should be4 reported and investigated of cables through pulleys, etc. further. (4) Check spring tension, brackets, braces, (10) On rolling lifts, check segmental rim and connectors of power cable reels. and girder, and the track plate and girder for : (5) Check travel rollers and guides, brakes, (a) Extension of rim plates and track limit switches, and stops. plates in either direction. (6) Since the machinery room is usually (b) Wear and poor fit of toothed rim and under the main deck, check the ceiling of the track plates, including cracking in the corners machinery room for leaks or areas that allow of the slots in the rim plates and fractured debris and rust to fall on the machinery. teeth. (7) Survey lift bridges, including towers, (c) Distortion of rim and track plates to check both horizontal and vertical displace- including curling of edges and separation of ments. This should identify any foundation plates froth their supporting girders. movements that have occurred. (d) Cracking at the fillets of the angles e. Control House. forming the flanges of the segmental and track (1) Consult with the bridge operator to as- girders. certain whether there are any changes from the (e) Cracking of the concrete under the normal in the operation of the bridge. track. (2) Note where the control panel is located (f) Looseness between walking pinion in relation to roadway and waterway. gear and top rack. Check top rack for lateral (3) Note whether the bridge tender has a movement when bridge is in motion. good line of sight view of approaching boats (g) On heel trunnion (Strauss) -bas- and vehicles. cules, check the strut connecting the counter- (4) Note whether structure shows cracks. weight trunnion to the counterweight for fa- Determine whether it is wind-proof and insu- tigue cracks. On several bridges, cracking has lated. been noted in the web and lower flanges near (5) In some cases only control boxes are the gusset connection at the end nearer the provided without a bridge tender. Note this sit- counterweights. The crack would be. most no- uation and check the security system. ticeable when the span is opened. (6) If controls are separate, note descrip- (h) The rack and pinion should be in- tion of bridge tender's house or shed, and inspected for gear wear, cleanliness and corrosion. clude its condition as well as the information d. V erticalLifts. about the control house. (1) Check span and counterweight guides (7) Note whether all Coast Guard, Corps for proper fit and free movements. Span guides of Engineers and local instructional bulletins are usually castings attached to suspended span are posted. chords which engage a T-section attached to the . (8) Note whether alternate warni..g de- tower. Counterweight guides are angles or tees vices such as bull horns, lanterns, flasher lights, attached to the tower and engaging grooved or flags are available. castings attached to the counterweights. These (9) Check for obvious hazardous operating grooved ,castings must be inspected closely for conditions involving the safety of the operator wear in the grooves. Check cable hold-downs, and maintenance personnel. turnbuckles, cleats, guides, clamps, and splay- (10) Check for any ,accumulations which casti ngs. may be readily combustible.

5-116 (11) Check controls and electric panels on (f) Determine whether the line or trans- movable structures. An electricalspecialist formers should be replaced or relocated. should be available for this part of the inspec- (g) Check lightning arrester device for tion. signs of distress. (a) Check controllers while bridge is (2) Submarine Cables. opening and closing.. Look for excess play and (a). Indicate the size and number of con- sparks.Check electricalcabinetsforloose ductors in the submarine cable. This is very im- wires, heaters and bunched-up wires. Note de- portant. Indicate the number of conductors bris or material hidden in cabinets. being used, the number of spares that are avail- (b). Inspect the electrical system of the able, and the number of conductors that have bridge including the wiring, conduiti,, motors, failed. This should equal the total number of and lights. conductors in the cables. (c) Check for worn or broken lines. (b) Note whether the cable is protected (d) Check for any existing hazardous from boats and the public, and whether it is condition. behind the fender system. (e) Check for rusted-out or mismatched (c) Note whether the cable is kinked, members. hooked, or exposed either above or below the (f) Determine whether the controller is water. outdated or parts need replacement. (d) Note wheth-er the ends are condi- (g) Determine whether electrical inter- tioned and protected from moisture. lock is working. (e) Check the cable at tidal areas for (h) Check whether panel doors are se- excess marine or plant growth. cured. (f) If cable has been spliced, note condi- .(i) Note whether bridge tender has any tion of box seal. complaints about the panel. (g) Inspect clamps and securing clips. (j )Check span speed control resistor h. Auxiliary Power. banks for overheating. (1) Operate auxiliary power or crank.and (12) Check the bridge operator's log. note condition and reliability. f. Storage Facilities. Check all storage facili- (2) On double leaf bascules, note whether ties for flammable material and any accumula- both sides have axiliary power systems. tion which may be readily combustible. (3) On hand cranked systems: (a)Determine whether standing plat- g. Main and Submarine Cables. forms are free of grease and debris. (1) Main cables. (1),) Determinethe number of men (a) Note the condition orthe power lines needed in this operation. coming to the bridge. (c) Determine whether a portable gener- (b) Where high voltage lines come all ator powered mechanical device can replace the the way to a transformer in the control house, manpower needed to operate the bridge. check that the main lines or cables are fully insulated and out of reach of the public. (c) Where transformers-are on a power Section 33. UNDERWATER INVESTIGATIONS pole near the bridge, cheCk the rigidity of the pole, guy lines, ground line, and cable to bridge. 5-33.1 General. (d) Check the transformer in the control Underwater investigation is a highly special- house, if any, for bracing, high voltage cables ized area. This type of bridge investigation is insulation loss, leaks, and cable protection. outside the normal duties of the bridge inspec- (e) If a cable is attached to the bridge, tor. Whenever underwater investigations are check anchors, clips, concrete bases, insulators, necessary they should be conducted by the per- or armor, for attached growth or debris. sonnel experienced in these types of inspections. 5-117 , However, the bridge inspector is still responsi- ment of scour holes, unintended exposure of pil- ble for the bridge inspection and for the evalua- ing, and the condition and effect of any scour tion of the underwater portions of the bridge. control installations. However, it is preferable The importance of such inspections on trestle to conduct scour investigations from the sur- and pile bent bridges cannot be overestimated. face, if possible. Relatively new structures have collapsed due to the corrosionof the steel piles below the con- e. Underwater Cables. Cables should be inves- crete protection. Prestressed concrete piles are tigated for the following: not immune to failures below water level, while (1) Damage to the cable from vessels or timber piles are also known to be vulnerable. floating objects. Investigation of such corrosion, or other deteri- (2) Kinks in the cable. oration, is especially important in sea water, which is four times as deleterious as fresh (3) Exposure of the cable when it should be buried. water. (4) Age and condition of the cable, and any need for replacement. 5-33.2 What to Look for During Inspection. (5) If the cable location is not as charted, a. Pile Bents. Check piles of all materials plot the current cable location. below the water line for any signs of deterioration or damages. 5-33.3 The Diver. (1) Steel Piles. Steel piles are susceptible to corrosion in the splash zone and tidal zone, Diving confronts a diver with forces and physi- and have been found to be severely perforated ological effects which are not encountered in at deeper water depths. Where piles are con- his normal environment. Each type of diving crete-jacketed in the tidal zone, the diver should equipment and operation gives rise to unique carefully check for signs of corrosion from the demands for safety precautions. The diver's area just below the concrete jacket all the way safety depends upon his knowledge of the fac- down to the mud line. tors which constitute safe working conditions, (2) Timber Piles. Timber piles should be and upon his ability to recognize unsafe condi- observed carefully from the water level to the tions. While diving operations will normally be mud line for marine borer and shipworm at- conducted and supervised by specialist person- tacks on timber pilings. nel, it is incumbent upon the bridge inspector to (3) Prestressed Piles. Check prestressed assist in these operations in whatever way pos- piles for longitudinal cracking. Pay particular sible. In order to assist the diver in his duties: attention to hollow prestressed piles. a. Define exactly what bridge components the (4) Piles Under Piers. The above instruc- diver is to inspect. tions also apply to piles under piers where the footing is set above the river or harbor.bottom. b. Ensure that he is thoroughly aware of what inspection task or tasks he is to accom- b. Dolphins and Fenders. Dolphins and fend- plish. ers should be examined below the water for deterioration and borer attack, and for any dam- c. Provide him with any reference data, such age caused by vessels or large floating objects. as previous inspection reports, which may be helpful. c. Pier and Abutment Conditions. Where the substructures are exposed below water, they d. Prepare, as much as practical, the bridge should be examined for any deterioration of the inspection site beforehand. Often a substantial concrete or of the rubble masonry piers, for loss amount of marine growth and barnacles can be of protective stone facing, and for any indica- cleaned from piles, and other areas to be in- tion of oier movement's. spected, by working from a boat. d. Scour. The river bottom arouud the piers e. Ensure that a boat, with a trained crew, is or abutments should be checked f or develop- ready. .

5-118 Section 34.SUSPENSION SPANS face of their concrete embedment for possible corrosion, deterioration, or movement. 5-34.1 General. (2) Check the entire visible (unencased) Suspension bridges are normally constructed portion of the anchor chain for corrosion or only when the more conventional types of signs of distress. bridges are impractical because of clear span b. Strand Shoes. Check the strand shoes on requirements or because the use of intermedi- parallel wire type bridges for signs of displaced ate piers is not feasible.Suspension bridges shims, movement, corrosion, misalignment, and may be categorized by the method of anchorage cracks in the shoes. used, the type of cable used, or a combination of c. Strand Sockets. Check the strand sockets at both. the anchorages of prefabricated strand type a. Anchorage. bridges for signs of movement, slack or sag, (1) Conventional or Independent Anchor- corrosion, broken sockets, and unpainted or ages. These bridges rely on anchoring ends of rusty threads at the face of sockets. Unpainted the cables by using either massive blocks of con- or rusty threads may indicate possible "backing crete or masonry, or by tunneling into rock. off" of nuts. (2) Self-Anchored. These bridges have no d. Wires in Anchorage. In parallel wire type means for massive external anchoring of the bridges, check the unwrapped wires between main cable. The main cables of these bridges the strand shoes and the splay saddle by care- are anchored by redirecting the horizontal com- fully inserting a large screwdriver between the ponent of the cable pull back into the bridge wires and applying leverage. This test will re- structure itself. However, a portion of the verti- veal the presence of broken wires for some dis- cal cable reaction is absorbed by the anchor tance past the splay saddle under the wrap- piers. pings. (Only random checking is required.) b. Cable. e.Strands at Anchor Sockets. Check the (1) Parallel Wire. This type of bridge is strand at its entrance to the socket for signs of supported by main cables made up of a series of possible abrasion, corrosion, or movement. parallel wires spun in place, compressed and wrapped. f. Main Suspension Cables. Check for corroded wins. Examine the condition of the pro- (2)Prefabricated Bridge Strand. This tective covering or coating of the main suspen- type of bridge is supported by main cables made sion cables, especially at : up of a series of bridge strands (either parallel or twisted wire), fabricated, stretched, and (1) Areas adjacent to the cable bands. socketed in the shop and then shipped to the (2) Saddles over towers, cable bent piers bridge site on reels. These strands are erected and at anchorages. one at a time; they may or may not be wrapped. g. Splay Saddles. Check the splay saddles for : (3) Eye Bar Chain. This type of bridge is (1) Missing or loose bolts. supported by main chains made up of a series of (2) Movement up the cable away from the eye bars connected with pins. There are few splay. Signs of this movement may be the ap- bridges of this type remaining in this country. pearance of unpainted strands on the down hill c. Suspension Bridge Components. The dis- side or "bunched up" wrapping on the uphill cussion in paragraph 5-34.2 will be limited to side. the cable and its connections only. All other (3) The presence of cracks in the casting bridge components will be inspected in detail as itself. covered in other sections of this manual under h, Cable Bands. Check the cable bands for : their respective types. (1) Missing or loose bolts. (2) Possible slippage. Signs of this move- 5-34.2 What to Look for During Inspection. ment are caulking that has pulled away from a. Anchor Bars or Rods. the casting or "bunching up" of the soft wire (1) Check all anchor bars or rods at the wrapping adjacent to the band.

5-119 (3)The presence of cracks in the band it- i. Saddles. Check saddles for : self. (1) Missing or loose bolts. (4)Broken suspender rope saddles. (2) Slippage of the main cable. (3) Corrosion or cracks in the casting. (5)Corrosion or deterioration of the band. (4) Connection to top of tower or support- (6)Loose wrapping wires at the band. member.

Anchor Rods Strand Sockets Hand Rope Splay Saddle Cable Bands Stanchion Main Cable Saddles Tower Suspender Ropes Cable Beni Sofi Wire Wrapping Suspender Sockets Gravity Anchor Stiffening Truss or Girder Tunnel Anchor (Preformed Sirands)

Gravity Anchor (Spun in7 place Strands)

Figure 5-140.Suspension bridge features.

5-120 j: Hand Ropes and Connections. Check hand (1) Corrosion, cracks, or deterioration. ropes and connections for : (2) Abrasionatconnectiontobridge (1) Loose connectionsofstanchionto structure. cable bands. . (3) Possible movement. (2) Too much slack in rope. m. Anchorages. The anchor chain gallery of 43-) ent or twisted stanchions. the anchorage is usually a dark damp enclosure (4) Loo e connections. at anchorages or with a very corrosive atmosphere. The interior towers. should be inspected for the following: (5) Corroded or deterioratedropesor (1) Corrosion and deterioration of any stanchions. steel hardware. k. Suspender Ropes. Check suspender ropes (2) Protection against water entering or for : collecting where it may cause corrosion. (1) Corrosion or deterioration. (3) Proper ventilation. (2) Kinks orslack. n. Wrapping Wire. Check to see that there (3) Abrasion or wear at-sockets, saddles, are no loose wrapping wires or cracks in the clamps, and spreaders. caulking where water can enter and cause cor- (4) Broken wires. rosion of the main cable. Check for evidence of water seepage at cable bands, saddles and.splay

1. Suspender Rope Sockets. Check sockets for : castings. .

5-121 CHAPl'ER VI

REPORTS AND RECOMMENDATIONS-

Section1. REPORTS tional inspection of bridges immediately following any natural or man-causedoccurrence 6-1.1 Introduction. which might have lessened the structural integ- In the preceding chapter the factors, conditions, rity of a bridge, is to: and situations which cause bridge deterioration (1) Provide an information base for imme- were described in considerable detail. The in- diate action to limit the use of, or to close to tent of this chapter is to outline the objectives traffic, any bridge which inspection has revealed of bridge inspection reports, discuss generally to be hazardous to public safety. the uses of bridge inspection reports, and em- (2) Determine the extent of any weakness phasize the importance of preparing practical or structural damage, critical or minor, result- documented recommendations for actions to be ing from normal deterioration or fromany taken, based upon the specific bridge inspection other cause. finding. (3) Develop a chronological record of the conditions of the bridge, thus providing a basis 6-1.2 Reports. for analyzing the significance of structural changes. a. General. The bridge inspection report is an extremely valuable document when completed (4) Enable bridge maintenance to be pro- properly. A new inspection report should be grammed more effectively through early detec- made each time a bridge isinspected. To tion of structural defects or deficiencies, thus achieve maximum effectiveness, each report minimizing repair costs. should be supplemented with sketches, photo- (5) Maximize public safety through the graphs, or any other additional explanatory in- elimination or correction of hazardous condi- formation: Reports and supplemental informa- tions:--- tion must be accurate, and amplifying descrip- (6) Assist in the replacement program- tionsor explanationsshouldbeclear and ming of bridge structures. concise. A well prepared report will not only provide information on existing bridge condi- 6-1.3 Uses of Bridge Inspection Reports. tions but also becomes an excellent reference a. Bridge inspection reports provide an infor- source for future inspections, comparative anal- mational record of the current analyses of simi- yses, and for bridge study projects. Whenever lar bridge structures including such mattersas, confronted with a doubtful condition notov- but not limited to : ertly manifested as a defect or deficiency, but (1) Traffic density and its effects.' nevertheless suspicious, it should be reported. In doing so, however, the bridge inspector must (2) Nature, frequency, and extent of re- be careful to report the circumstances factually pairs by type. and avoid speculation, exaggeration, or supposi- (3) Safety records. tion. Further action on such reports will be de- (4) Specific kinds of deterioration. termined after review and consultation by (5) Preventive maintenance programs. higher engineer authorities. b: Inspection reports of themselvesare insuf- b. Repoit Objectives. The purpose of system- ficient to guarantee the continued safe service atic periodic bridge inspections, and the addi- of the bridge. If the ultimate objective ofa bridge inspection programis to be achieved, it (2) Programmed repairs, those to be per- becomes necessary to.: formed sometime later. (1) Make a structural analysis of the The inspector must decide whether a repair is bridge to ascertain its safe load capacity for its urgent. Usually this is easily determined, but at current condition. other times the experience and professional (2) Restrict loads crossing the bridge so judgment of a graduate engineer may be re- that its computed safe capacity is not exceeded. quire to reach a proper decision. A rapidly en- (3) Perforn-r all maintenance necessary to larging hole through the deck of a bri.dg,e.:Al., prevent a decline in the load capacity of the viously needs attention, and a recommendation bridge or to increase the bridge capacity to a for emergency repair is in order. By contrast,a minimum essential level. slightly deteriorated gusset plate at a panel (4) Eliminate all known or suspected haz- point of a truss may not be critical. A condition ards to public safety. such as this would appropriately call for a recommendation for a programmed repair. When- ever emergency repairs are needed, i icommen- Section 2. RECOMMENDATIONS dations may call for repairs of a temporary nature. For example, a steel plate may be posi- 6-2.1 General. tioned,in place over a hole in the deck, ora a. A good inspection report will explain in dainaged beam may be supported temporarily detail the type and extent of any deterioration with timber. It must be realized, however, that detected on a bridge, and will point out any any temporary repair must later be integrated deviations or modifications that are contrary to into the annual maintenance program on the the "as built" construction plans of the bridge. basis of established orders of priority for work Not all conditions of deterioration are of equal completion. It may be recommended that re- importance. For example, a crack in a concrete pairs be made on a permanent basis, if such box beam which allows water to enter the beam repairs can be completed as quickly and as is much more serious than a vertical crack in efficiently as any available temporary means. the backwall, or a spall in a corner of a slope- Most recommendations concerning repairs sub- wall. The inspector, in formulating his recom- mitted by the bridge inspector will be in the mendation, must determine the seriousness of category of 'programmed repairs ;i.e., repairs the defect or deficiency involved. He must care- that will be incorporated into preprogrammed fully consider the benefits to be derived from repair and maintenance schedules. Figure 6.4 making the repairs, the cost involved, and the portrays- how inspection report recommenda- consequences if the suggested repairs are not tions might be processed. made: Following this he must judiciously weigh these considerations in arriving at reasonable 6-2.3 Cost Considerations. and practical conclusions. a. Whenever an inspector recoi 'mends that b. The recommendations made by the inspec- bridge repairs be made, he may describe fully tor constitute the "focal point" of the operation the type of repairs that are needed, the scope of of inspecting, recording, and reporting. A thor- work to be done, an estimate of the materials ough, documented inspectionisessential for that will be required to complete the proposed making practicalrecommendations, onsug- repairs, and when such repairs may be under- gested courses of action to correct or preclude taken. Such information will be used to deter- bridge defects or deficiencies. Theoretically, if mine : there are no recommendations, there is nothing (1) The priority for repair, and seriously wrong with the bridge structure. (2) T.he method of repair. More important, the cost of such repairs must 6-2.2 Categories of Repair. be reviewed and analyzed in the context of the Recommendations concerning repairs maybe overall mainterianearepair prograni. classified into two general categories: b. In order to arrive at the most effective, yet (1) UrgentlY'needed repairs, or economical, means of accomplishing repairs, it 6-2 is imperative that a comparison be made be- scheduled. If not, then the schedule needs to be tween alternatives. The availability of funds modified accordingly. Again, the element of cost may determine the type and extent of repairs is a deciding factor since even the administra- and will influence the priority of work assigned. If the recommended repairs are already pro- tive process of changing the order of scheduled grammed, then it must be decided whether the repairs involves costs. In addition, the delay of repairscan be accomplished asprevious?y already scheduled repairs may result in added

INSPECTION 1

I REPORT RECOMMENDATIONS L URGENT PROGRAMMED REPAIRS REPAIRS rpERMANENT TEMPORARY

PRIORITIES

WITHIN WITHIN BRIDGE STATE STRUCTURE

IMETHOD OF REPAIR

ESTIMATED COST AND SUPPORTING PLANS

REPAIRS TO BE PERFORMED REPAIRS TO BE PERFORMED BY STATE MAINTENANCE BY CONTRACT

RESTORATION WORK PERFORMED

IEVALUATION OF P.Zi-AIRS I

RECOMMENDATIONS 1 AFTER EVALUATION

Figure 6-1.Typical repair recommendation process. 6-3 costs since the conditions which were to be cor- The priority rating should be upgraded if there rected by such repairs may have become worse. is a high percentage of heavy laid traffic. c. The priority given to recommended repairs (d) Alternate Bridges. Lack of conven- may be one of urgency ; however, the pre$s of ient alternate bridges should upgrade the prior- other equally urgent repairs may dictate a reas- ity'of repairs. sessment of priorities and a review of available (e) Weather. Defects that would be ag- repair capabilities. If organizational repair cap- g-avated by adverse weather should be cor- abilities are unable to fulfill all repair require rected pr.icr to the. onset of extreme weather ments, contractural arrangements may have to conditions. be made. Should this course of action be fol- (f)TrafficFluctuations.If a bridge lowed, costs become a deciding factor. Everyone must be partially or totally closed for repairs, concerned should strive for that combination of this should be done when traffic density is rela- organization and contract capability which will tively low. provide for effective bridge repair at a re-sona- (g) Bridge Size. The size of any bridge ble .cost.Whatever course of bridge repair is an indication of its overall importance ; there- action is pursued, the prime dictate of such fore, bridge size will influence the priority action should be in the interest of public safety ranking for repairs. and public investment. (h) Geographical Location. Occasionally it may be economical to modify priorities for 6-2.4 Priorities. reasons of location. For instance, if two or more a. Priorities of repair are determined by a bridges are located in close proximity and re- number of factors in addition to engineering quire similar repairs, it may be more practical considerations. It may also be important to tocomplete thesebridges consecutivelyir- weigh environmental, economic, and social fac- respectiveofestablishedpriorities.Thus, tors. Although in many cases the priority will bridges ranked 8 and 11 according to a priority be set by one individual, the information sup- of repair might be repaired consecutively if plied by several persons will be instrumental in bridges 9 and 10 are comparable to them in de- reaching a sound decision. Priorities should be gree of deterioration. established on a statewide basis, as well as (i) Replacement. Any priority rating for within a smaller geographical area, such as a bridge repairs should consider whether the district. bridge in question is scheduled for replacement b. The following considerations should be and when closure or restricted access, if any, is taken into account in the establishment of to be effected. A bridge scheduled for replace- priorities for bridge repair. ment in the near future may warrant only temporary repair or, possibly, none at all depending (1) Factors. on the nature of the repairs. (a) Safety. Any condition which is con- (2) Intrct-Structure Priorities. An order of sidered unsafe, either from a structural (e.g., priorities within each individual bridge struc- disintegrated pier cap) or user (e.g., weakened ture may also be established based upon struc- railing) viewpoint, should be assigned a high tural importance and degree of deterioration. It priority for correction. is preferable to list the various items that need (b) Condition of Structure. The most repair according to structural significance. Such important factor in establishing repair priori- a listing will permit the report reviewer to de- ties is the degree of deterioration of the struc- termine immediately what the most serious de- ture. It is essential for the inspector to provide fects are, and will assist him in ordering the complete and accurate data in order to permit a priority of repairs for that structure. valid analysis of the structure. (c) Density of Traffic. Where bridge de- 6-1.5 Summary. teriorationisapproximatelyequivalent,a higher priority probably should be assigned to Methods and standards for the inspection of the bridge serving the greater density of traffic. bridges, while not universal in application, 6-4 have, nevertheless, been established through ex- entiously recorded in detail. Those conditions perience. These methods and standards have which currently or potentially injurious to been developed, modified, and refined for the the bridge, regardless of how small or seem- purpose of preserving theintegrity of the ingly unimportant they may appear, must also bridge structure in the interests of public safety be included in his report of inspection. and service. Chapter V pointed out the characteristics of those conditions which cause deteri- The importance of well-formulated and docu- oration and which the inspector should be mentedrecommendationscannot beover 10.enly aware of during the course of his inspec- stressed. Their content provides the basis for: tion routine. Obviously, the bridge inspector (1) the elimination of hazards to public and cannot be a superficial observer. Whenever the bridge safety, (2) remedial repairs, and (3) the bridge inspector is engaged in the task of in- eliminationofinadequaciesaffectingthe specting and assessing the conditions of any bridge.' Therefore, itis incumbent upon the bridge, he must be thorough in his application bridge inspector, whenever the occasion arises, of bridge inspection techniques. His investiga- to prepare meaningful recommendations which tions must be complete and his findings consci- can be clearly and easily understOod.

6-5 GLOSSARY

A L-Abutment. A cantilever abutment with the stem flush with the toe of the footing, forming Abutment. A substructure composed of stone, an L in cross section. concrete, brick, or timber supporting the end of a single span or the extreme end ofmultispan Spill-Thru Abutment. Consists essentially of superstructure and, in general, retaining or two or more columns supporting a grade beam supporting the approach embankment placed in spanning the space between them. The ap- coact therewith. Figure 5-36. (See also RE- proach embankment is retained only in part by TAINING WALLS, WING WALLS.) the abutment since the embankment's sloped front and side portions extend with their nor- The following types are now commonly used : mal slope to envelop the columns. Also called an Cantilever Abutthzrts. An abutment in which arched abutmwit. the stem or breast wall is fixed rigidly to the ShoulderAbutment.(Full-HeightAbut- footing. The stem, acting as a cantilever beam ment.) A cantilever abutment extending from transmits the horizontal earth pressure to the the grade line of the road below to that of the footing, which maintains stability by virtue of road overhead. Usually set just off the shoulder. the dead weight of the abutment and of the soil mass resting on the rear portion, or heel, of the Semi-Stub Abutment. Cantilever abutment footing. founded .part way up the slope, intermediate in size between a shoulder abutment and a stub Cellular Abutment. An abutment in which abutment. the space between wings, breast wall, approach slab, and footings, instead of containing the ap- Straight Abutment. (Trapezoidal or Block.) proach fill, is hollow. This amounts to an R/C An abutment whose stem and wings are in the box or boxes comprising the abutment. On same plane or whose stem is included within a some bridges curtain walls are placed between length of retaining wall. In general, the stem the pier and abutment to simulate a cellular wall is straight but will conform to the alignment of the retaining wall. abutment. 1 Stub Abutment. (Perched Abutment, Dwarf Counterforted'Abutment. Anabutment Abutment.) An abutment within the topmost which develops resistance to bending moment portion of the end of an embankment or slope (or horizontal force)in the stem by use of and, therefore, having a relatively small verti- counterfortS. This permits the breast wall to be cal height. While often engaging and supported designed as a horizontal beam or slab spanning between counterforts, rather than as a vertical upon piles driven through the underlying embankment or in-situ material, stubs may also be cantilever slab. founded on gravel fill, the embankment, or nat- Gravity Abutment. A heavy abutment which ural ground itself. resists the horiiontal, earth pressure by its own Aggregate. The sand, gravel, broken stone, or dead weight. combinations thereof with which the cementing Integral Abutment. A small abutment cast material is mixed to form a mortar or concrete. monolithically with the end diaphragm of the The fine material used to produce mortar for deck. Although such abutments usually encase stone and brick masonry and for the mortar the ends of the deck beams and are pile sup- component of concreteis commonly termed ported, spread footings with acombination "fine aggregate" while the coat- se material used backwall and end diaphragm mayalso be used. in concrete only is termed "coarse aggregate." Allowable Unit Stress. See STRESS. material will slide upon itself froma higher to a Anchorage. The complete assemblage ofmem- lower elevation. At all angles less thaan theangle bers and parts whether composed of metal,ma- of repose, the particles of earthare ;eld in equi- sonry, wood or other material designed to hold librium by the forces of gravity andfriction. in correct position the anchorspan of a canti- Relatively slight variations in the quantity of lever bridge, the end of a suspensionspan cable contained moisture produce marked differences or a suspension span backstay; the end of a in the angle of repose. The inclinedsurface of a restrained beam, girder or trussspan; a retain- cut or of an embankment either naturallyor ing wall, bulkhead, or other portionor part of 'a artificially produced at the angle ofrepose is structure. commonly described as being at "natural slope." Anchor Span. The span which in conjunction Anisotropy. The property ofsome engineering with the uplift resisting anchorage device(if materials, such as wood, exhibiting different any) located at its outermost end, counterbal- strengths in different directions. ances and holds in equilibrium the fully canti- Approach Slab. A heavy R/C slab placedon the levered portion or arm extending in the opposite approach roadway adjacent to and usuallyrest- direction from the major point of support. See ing upon the abutment back wall.The function CANTILEVER BEAM, GIRDER, OR TRUSS. of the approach slab is tocarry wheel loads on Anchor Bolt. A bolt-like piece of metalcom- the approaches directly to the abutment,pre- monly threaded and fitted witha nut, or a nut venting the transfer ofa horizontal dynamic and washer at one end only, used tosecure in a force through the approach fill tothe abutment fixed position upon the substructure the end of stem. a truss or girder, the base of a column, a pedes- Apron. A waterway bed protection consistingof tal, shoe, or other member ofa structure. The timber, concrete, riprap, pavingor other con- end intended to engage themasonry may be struction placed adjacent to substructureabut- formed in various ways depending somewhat ments and piers to prevent underminingby upon the conditions attending its setting in final SCOUT. position. Among these are the following: Arch. In general, any structure producingat its Hooked. Bent either coldor in a heated condi- supports reactions having both verticaland tion to form a hook-like anchorage. The hooked horizontal components. However, thisdefinition bolt is commonly built into themasonry prelim- is not intended to include structuresof the rigid inary to the placing of the member to bean- frame type, although applicable thereto,but in- chored and it may, therefore, be utilizedto en- stead to apply only to those havingthroughout gage an anchor bar or other device imbedded in their length a curved shape, either actualor the masonry. approximated. Ragged, Barbed or Fanged. Cut witha chisel Specific types of arches adapted to bridge to produce fin-like projectionsupon the surface. construction derive theirnames either from the form of curve ( or combination ofcurves as- Threaded. Shaped witha machine -cut thread. sumed for the development of their intradosal The thread anchor- geis commonly supple- .surfaces), the support conditions,or their type mented by a -nut, or a nut and anchorplate, of construction. The following constitutea por- when the bolt is to he built into themasonry tion/of the types inuse: instead of being set ir_ a drilled hole. Elliptic Arch. One in which the intradossur- Swedged. (Notch. 30., Hacked.) Indentedand face is a full half of the surface ofan elliptical bulged by swedging c.r nicked transversely and cylinder. This terminology is sometimesincor- diagonally, or both, h y.cutting witha chisel. rectly applied to a multicentered arch. (An el- Angle of Repose. (A ogle of Internal Friction.) liptic arch is fitted to stonemasonry arches.) As applied to approach embankmentsor other Circular Arch. One in which the intradossur- earthwork construction :the batteror slope face is a portion of the surface ofa right circu- angle with the horizontal at whicha given earth lar cylinder.

G-2 Multi-Centered Arch. One in which the intra- Arch Barrel. An arch ring that extends the dos surface is outlined by two or more arcs hav- width of the structure. ing different radii by intersection tangentially and disposed symmetrically. Arch. Rib. An arch ring unit used in unfilled and open spandrel arch construction in rein- Open Spandrel Arch. An arch having span- forced concrete. Two or more relatively narrow drel walls with its spandrel unfilled. The arch arch rLig units or sections support the columns ring receives its superimposed loads through of the bays or panels. The construction may in- these walls and, if necessary, through interior volve a combination of arch ribs with spandrel spandrel walls, tie or transverse walls, and/or walls providing an outward appearance akin to interior columns. that of an unfilled spandrel arch. A structure having the spandrel walls re- One of the arched girders of a plate girder placed by bays or panels with arches, lintel rib arch. spans, or other constructions supporting the deck construction and these in turn supported Arm. 1. The portion of a swing bridge or of a by cross walls or columns resting upon the arch retractile draw bridge which forms the span or ring. See OPEN SPANDREL RIBBED ARCH. a portion of the span of the structure. 2. The rear or counterweight leaf of a bascule span. 3. Open Spandrel Ribbed Arch. A structure in The overhanging (or cantilever) portion of a which two or more comparatively narrow arch cantilever bridge which supports the suspended rings function in the place of an arch barrel. span. 4. In statics, the perpendicular distance The ribs are rigidly secured in position by arch between the two parallel equal and opposite rib struts located at intervals along the length forces of a moment. of the ring. The arch rings support a column type open spandrel construction sustaining the Armor. A secondary steel member installed to floor system and its loads. protect .a vulnerable part of another member, e.g., steel angles placed over the edges of a Parabolic Arch. One in which the intrados joint. surface is a segment of a symmetrical parabolic surface (suited to concrete arches). Axle Load. The load borne by one axle of a traffic vehicle, a movable bridge, or other mo- Spandrel Arch. A stone or reinforced con- tive equipment ordevice and transmitted crete arch span having spandrel walls to retain through a wheel or wheels to a supporting the spandrel fill or to support either entirely or structure. in part the floor system of the structure when the spandrel is not filled. B Segmental Arch. An arch in which the intrados surface is less than half of the surface of a Back. See EXTRADOS. cylinder or cylindroid. Likewise it may take Backfill. Material placed adjacent to an abut- shape wherein any right section will show a ment, pier, retaining wall or other structure or parabolic curvature. part of a structure to fill the unoccupied portion Two-Hinged Arch. An arch which is sup- of the foundation excavation. ported by a pinned connection at each support. Soil, usually granular, placed behind and within the abutment and wingwalls. Three-Hinged Arch. An arch with end supports pinned and a third hinge (or pin) located Backstay. The portion of the main suspension somewhere near mid-span making the structure member of a suspension bridge extending be- determinate. tween the tower and the anchorage. When this member continues over the towers from anchor- Voussoir Arch. A hingeless arch with both age to anchorage, it does not support any por- supports fixed against rotation. Originally built tion of the bridge floor system which may be of wedge-shaped stone blocks or voussoirs, the located between the tower and anchorage hingeless arch may also be built of concrete. members of the structure.

G-3 A cable or chain attached at the top of a shape from round to square. See BALUS- towec and extending to and secured upon the TRADE. anchorage to resist overturning stresses exerted upon the tower by the suspension span attached Balustrade. A railing composed of brick, stone to and located between towers. or reinforced concrete located upon the retaining wall portion of an approach cut, embank- Backwall. The topmost portion of an abutment ment or causeway or at the outermost edge of above the elevation of the bridge seat, function- the roadway or the sidewalk portion of a bridge ing primarily as a retaining wall with a live to serve as a protection to vehicular and/or pe- load surcharge. It may serve also as a support destrian traffic. Its major elements are :(1) for the extreme end of the bridge deck and the plinth, (2) balusters, and (3) capping: How- approach slab. ever, the web portion may be built without Backwater. The water of a, stream retained at openings instead of balustered ,-,or other open an elevation above its normal level through the construction. See PARAPET. controlling effect of a condition existing at a Base Metal, Structure Metal, Parent Metal. The downstream location such as a flood, an ice jam metal at and closely adjacent to the surface to or other obstruction. be incorporated in a welded joint which will be The increase in the elevation of the water fused, and by coalescence and interdiffusion surface above normal produced primarily by with the weld will produce a welded joint. the stream width contraction beneath a bridge. Base Plate. A plate-shaped piece ofsteel, The wave-like effect is most pronounced at and whether cast, rolled or forged, riveted upon or immediately upstream from an abutment or pier by other means made an integral. part of the but extends downstream to a location beyond base portion of a column, pedestal or other the body of the substructure part. member to transmit and distribute its load ei- Balance Blocks. Blocks of cast iron, stone, con- ther directly or otherwise to the substructure or crete or other heavy weight material used to to another member. adjust the counterbalance of swing and lift Batten Plate. 1. A plate useci to cover the joint spans. formed by two abutting metal plates or shapes Balance Wheel. (Trailing Wheel.) One of the but ordinarily not considered as serving to wheels attached to the superstructure, normally transmit stress from one to the other. 2. A plate having only a trailing contact upon a circular used in lieu of lacing to tie together the shapes track surrounding the pivot of a center bearing comprising a built-up member. 3. A term some- swing bridge. These wheels maintain the proper times used as synonymous with Stay Plates to balance and lateral stability of the superstruc- indicate a plate in which the bar latticing or ture by preventing excessive rocking or other lacing of a bolted, riveted, or welded member motion due to wind pressures, shock from oper- terminates. ating irregularities, or other causes. When cor- Batter. The inclination of a surface in relation rectly adjusted, a balance wheel will transmit to a horizontal or a vertical plane or occasion- only its own weight to the track and will re- ally in relation to an inclined plane. Batter is volve without load upon its axle. commonly designated upon bridge detail plans Balancing Chain. See COUNTERBALANCING as so many inches to one foot. See RAKE. CHAIN. Batter Pile. A pile driven in an inclined position Ballast. Filler material, usually broken stone or to resist forces which act in other than a verti- masonry, used either to stabilize a structure (as cal direction. It may be computed to withstand in filling a crib) or to transmit a vertical load to these forces or, instead, may be used as a sub- a lower level (as with a railroad track ballast). sidiary part or portion of a structure to improve its general rigidity. Baluster. One of the column-like pieces compos- When driven and made fast upon the end of a ing the intermediate portion of a balustrade. pile bent or a piled pier located in a stream, Balusters may be varied incross-sectional river, or other waterway, it functions as a

G-4 cutwater in dividing and deflecting floating ice perfection of the masonry plate and bearing and debris. surface, to seal the interface, and to aid in even Bay. As applied to a stringer of multibeam distribution of loads at the interface. The bearing pads may be made of alternating layers of structure, the area between adjacent stringers. red lead and canvas, of sheet lead, or of pre- Bead. (Run.) A narrow continuous deposit of formed fabric pads. weld metal laid down in a single pass of fused filler metal. BearingSeat. Top of masonry supporting bridge bearing. Beam. 1. A simple or compound piece receiving and transmitting transverse or oblique stresses Bearings. (Live Load, Front Load, Outer.) Live produced by externally applied loads, when sup- load bearings are a class of special bearings or ported at its end or at intermediate points and supports installed on movable swing and bas- ends. The beam derives its strength from the cule spans. These are engaged when the bridge development of internal bending or flexural is in the closed position taking the load off the stresses. 2. A rolled metal I-shaped or H-shaped trunnions and center pivot and preventing the piece. 3. An I-shaped piece or member composed outer end of the lift span from hammering on of.plates and angles or other structural shapes the rest pier under live load. Front load bear- united by bolting, riveting or welding. In gen- ings are live load bearings placed on the sup- eral, such pieces or members are described as port pier of a bascule bridge, and outer bear- built-up beams. These terms are applied to and ings are those on swing span and bascule rest define,in general terms only, variations in piers. shape, size and arrangement of beam type members of reinforced concrete structures. Bed Peck. (Ledge Rock.) A natural mass for- mationofigneous,z.-2.1rner.tary,ormeta- Reinforced Concrete Beam. Reinforced con- morphic rock material either .-2utcroroiiir, np.)n crete beam is a construction wherein the tensile the surface, uncovered in , excava. stresses, whether resulting from bending, shear, tion, or underlying an:cumulation of uncon- or combinations thereof produced by transverse solidated earth material. loading, are by design carried by the metal reinforcement. The concrete takes compression (and Bench Mark. A point of known elevation. some shear) only. It is commonly rectangular or Bent. A supporting unit of a trestle or a viaduct Tee-shaped with its depth dimension greater type structure made up of two or more column than its stem width. or column-like members connected at their top- ReinforcedConcreteT-Beam.Reinforced most ends by a cap, strut, or other membe: concrete T-beam derives its name from a simi- holding them in their correct positions. Ti. ;s larity of shape to the letter "T," the head connecting member is commonly designed to or topmost element of the letter consisting of a distribute the superimposed loads upon the portion of the deck slab which is constructed bent, and when combined with a system of diag- integrally with the 11/C beam stem. onal and horizontal bracing attached to the columns, the entire construction functions some- Bearing Failure. Concerning the usual materi- what like a truss distributing its loads into the als of construction, a crushing under extreme foundation. compressive load on an inadequate support ; When piles are used as the column elements, concerning soil, a shear fail; re in the support- the entire construction is designated a "pile ing soil caused by excessively high pressures bent" or "piled bent" and, correspondingly, applied by a footing or pile. when those elements are framed, the assem- Bearing. (Fixed.) A bearing which does not blage is termed a "frame bent." allow longitudinal movement. Berm. (Berme.) The line, whether straight or Bearing Pad. A thin sheet of material placed curved, which defines the location where the top between a masonry plate and the masonry bear- surface of an approach embankment or cause- ing surface used to fill any voids due to im- way is intersected by the surface of the side

G-5 slope. This term is synonymous with "Roadway oped by the force tending to produce movement Berm." or slippage at the interface between the con- A horizontal bench located at the toe of slope crete and the metal reinforcement bars or other of an approach cut, embankment or causeway to shapes. strengthen and secure its underlaying material Bowstring Truss. A general term applied to a against sliding r.r other displacement into an truss of any type having a polygonal arrange- adjacent ditch, borrow pit, or other artificial or ment of its top chord members conforming to or natural lower lying area. nearly conforming to the arrangement required Blanket. A protection against stream scour for a parabolic truss. placed adjacent to abutments and piers and cov- A truss having a top chord conforming to the ering the stream bed for a distance from these arc of a circle or an ellipse. See PARABOLIC structures considered adequate for the stream TRUSS. flow and stream bed conditions. The stream bed covering commonly consists of a deposit of Box Beam. A rectangular-shaped precast, and stones of varying sizes which, in combination, usuallyprestressed,concretebeam. ...These will resist the scour forces. A second type con- beams may be placed side by side, connected sists of a timber framework so constructed that laterally, and used to form a bridge deck, with it can be ballasted and protected from displace- or without a cast-in-place slab or topping. In ment by being loaded with stones or with pieces such cases, the beam units act together similar of wrecked concrete structures or other adapta- to a slab. Where a C-I-P slab is used and the ble ballasting material. units are spreac, they act as beams. Box Girder (concrete). A large concrete box- Bcster. A block-like member composedof wood, metal, or concrete used to support a bear- shaped beam, either reinforced or prestressed, ing on top of a pier cap or abutment bridge usually multi-celled with several interior webs. seat. It may adjust bearing heights and avoid The bottom slab of the girder serves as a flange constructing the bridge seat to the crown of the only, while the top slab is both a flange and a roadway, provide an area that may be ground transverse deck slab. to a precise elevation, or raise a bearing above Box Girder (steel). A steel beam or girder, with moisture and debris that may collect on the arectangularortrapezoidalcrosssection, bridgeseat.Seealso BRIDGE PAD and composed of plates and angles or other struc- BRIDGE SEAT PEDESTAL. tural shapes united by bolting, riveting, or welding, and having no interior construction Bolted Joint. See RIVETED JOINT. except stiffeners, diaphragms, or other second- Bond. 1. In reinforced concrete, the grip of the ary bracing parts. concrete on the reinforcing bars, thereby pre- Recently, large steel multi-cell boxes with venting slippage of the bars. 2. The mechanical interior webs have been used as have composite bond resulting from irregularities of surface steel box girders in which the concrete slab produced in the manufacturing operations is an forms the top side of the box. important factor in the strength of a reinforced Bracing. A system of tension or of compression concrete member. For plain round bar rein- members, or a combination of these, forming forcement, it is the difference between the force with the part or parts to be supported or required to produce initial slip and the ultimate, strengthened a truss or frame. It transfers producing failure. "Deformed" bars utilize this wind, dynamic, impact, and vibratory stresses mechanical bond in conjunction with the sur- to the substructure and gives rigidity through- face bond. 3. The mechanical force developed be- out the complete assemblage. In general, the tween two concrete masses when one is cast against the already hardened surface of the bracing of a girder or of a truss span employs : other. (1) A system of horizontal bracing in the planes o! the top and bottom flanges or chords, Bond Stress. A term commonly applied in rein- designated according to its location, the top forced concrete construe 'on to the stress devel- flange, top chord, top or overhead lateral brae-

G-6 ing, and the bottom flange, bottom chord lower lateral bracing. Bridge. A structure providing a means of (2) Cross or X-bracing when placed trans- transit for nedestrians and/or vehicles above versely in vertical planes between beams and the land and/or water surface of a valley, ar- stringers and having diagonal members crossed, royo, gorge, river, stream, lake, canal, tidal sometimes termed "Cross Frame." It functions inlet, gut or strait : above a road, highway, rail- as a diaphragm. way or other obstruction, whether natural or (3) Sway or buck bracing when placed artificial. transverselyinverticalornearlyvertical In general, the essential parts of a bridge planes between trusses. The term "overhead are : (1) the substructure consisting of its abut- bracing," when applied here, is more appropri- ments and pier or piers supporting the super- ate than when applied to the top chord lateral structure, (2) the superstructure slab, girder, bracing. truss, arch or other span or spans supporting (4) Portal bracing consisting of a system the roadway loads and transferring them to the of struts, ties and braces placed in the plane, of sbstructure, and (3) the roadway and its inci- the end posts of the trusses. Portal bracing may dental parts functioning to receive and transmit be in the plane of one flange of the end posts traffic loads. and described as a "single plane" portal or it Bridge (composite). A bridge whose concrete may engage both flanges and be described as a deck acts structurally with longitudinal main "box portal." Without regard to its shape or carrying members. details the entire portal bracing member is frequently designated as a "portal." Bridge (indeterminate). A structure in which forces in the members cannot be determined by In general, the bracing of trestle and viaduct static equations alone. bents and towers employs : (1) Transverse bracing engaging the col- Bridge (prestressed). A bridge whose main umns of bents and towers in planes located ei- carrying members are made of prestressed con- ther perpendicular orslightlyinclined and crete. transversely to the bridge alignment. Bridge Pad. The raised, levelled area upon (2) Longitudinal bracing engaging the col- which the pedestal, shoe, sole, plate or other umns of bents and towers in planes located ei- corresponding element of the superstructure ther perpendicular orslightly inclined and takes bearing by contact. Also called Bridge lengthwise with the bridge alignment. Seat Bearing Area. (3) Horizontal bracing engaging the strut Bridge Seat. The top surface of an abutmc,tt yr members of the transverse and longitudinal pier upon which the superstructure span is bracing-of towers. Commonly this bracing is lo- placed and supported. For an abutment it is the cated in a horizontal position and is supported curface forming the support for the superstruc- against sagging by vertical hangers or ties. ture and from which the backwall rises. For a Bracket. A projecting support or brace-like con- pier it is the entire top surface. struction fixed upon two intersecting members Bridge Site. The selected position or location of to function: (1) as a means of transferring re- a bridge. actions or shear stress from one to the other, or (2) to strengthen and render more rigid a joint Bridging. A carpentry term applied to the connection of the members, or (3) to simply cross-bracing, nailed or rtherwise, fastened be- hold one member in a fixed position with rela- tween -wooden floor stringers, usually at the tion to the other. one-third span points, to increase the rigidity of the floor construction and to distribute more un- Breast Wall. (Face Wall, Stem.) The portion of iformly the live load and minimize the effects of an abutment between the wings and beneath the impact and vibration. bridge seat. The breast wall supports the superstructure loads, and retains the approach fill. Brush Curb. A narrow curb, 9 inches or less in width, which prevents a vehicle from brushing Brick Veneer. See STONE FACING. against the railing or parapet.

G -7 Buckle. To fail by an inelastic change in align- ceive the bridge floor loads and transmit them ment (usually as a result of compression). to the towers and anchorages. See SUSPEN- Buffer. (Bumper.) A mechanism designed to SION BRIDGE. absorb the concussion or impact of a moving Cable Band. The attachment device serving to superstructure or other moving part when it fix a floor suspender upon the cable of a suspen- swings, rises or falls to its limiting position of sion bridge. In general this device consists of a motion. steel casting provided with bolts or other appli- Built-Up Column. (Built-Up Girder.) A column, ances to securely seize it upon the cable and prevent the bank from slipping from its correct beam or girder, as the case may be, composed of plates and angles or other structural shapes location. united by bolting, riveting or welding to render Camber. The slightly arched form or convex the entire assemblage a unit. A built-up girder curvature, provided in a single span or in a is commonly described as a plate girder. multiple span structure, to compensatc..Lor dead Bulkhead. 1. A retaining wall-like structure load deflection and to secure a more substantial and aesthetic appearance than is obtained when commonly composed of driven piles supporting a wall or a barrier of wooden timbers or rein- uniformly straight lines are produced. In gen- forced concrete members functioning as a con- eral, a structure built with perfectly straight straining structure resisting, the thrust of earth lines appears slightly sagged. This optical illu- or of other material bearing against the assem- sion is unsatisfactory and is most manifest in blage. 2. A retaining wall-like structure com- relatively long structures over rivers or other posed of timber, steel, or reinforced concrete water areas. members commonly assembled to form a bar- The superelevation given to the extreme ends rier held in a vertical or an inclined position by of a swing span during erection to diminish the members interlocking therewith and extending deflection or "droop" of the arms when in open into the restrained material to obtain the an- position-cantilevered from the center bearing. chorage necessary to prevent both sliding and The decreased deformation below the normal overturning of the entire assemblage. position reduces the energy required to raise the ends in the closed position to permit the arms to Bumper. See BUFFER. function as simple spans. Buttress. A bracket-like wall, of full or partial Cantilever. A projecting beam, truss, or slab height, projecting from another wall. The but- supported at one end only. tress strengthens and stiffens the wall against overturning forces applied to the opposite face Cantilever Abutment. See ABUTMENT. by virtue of its depth in the direction of the Cantilever Bridge. A general term applying loads. A buttress may be either integral with or to abridge having a superstructure of the canti- independent of, but must be in contact with, the lever type. wall it is designed to reinforce. All parts of a buttress act in compression. Cantilever Beam, Girder, or Truss. A girder or truss having its members or parts so ar- Buttressed Wall. See RETAINING WALL. ranged that one or both of its end portions ex- Butt Weld. A weld joining two abutting sur- tend beyond the point or points of support. In faces by depositing weld metal within an inter- general, it may have the following forms :(1) vening space. This weld serves to unit the abut- two projecting ends counterbalanced over a ting surfaces of the elements of a member or to center support ;(2) a projecting end counter- join members or their elements abutting upon balanced in part by a portion extending beyond or against each other. the point of support in the opposite direction, and having at its end an uplift resisting anchor- C age to complete the condition of equilibrium or, instead, the counterbalancing portion or anchor Cable. One of the main suspension members of arm. may in itself be adequate to counteract the a suspension type bridge. Its function is to re- projecting portion ;(3) two projecting ends

G-8 with an intermediate suspended portion, whose the cement content of the mortar, concrete mix- weight is completely counterbalanced by the ture of inert aggregates, or hydraulic cement anchor spans and/or anchorages. The end por- and water. tions may or may not be alike in design. Center Bearing. The complete assemblage of Cantilever Span. A superstructure span of a pedestal castings, pivot, discs, etc., functioning cantilever bridge composed of two cantilever to support the entire dead load of a swing span arms or of a suspended span connected with one when the end lifts are released or the span is or two cantilever arms. revolving to "open" or to "closed position." Cap. (Cap Beam, Cap Piece.) The topmost piece Center Discs. The assemblage of bronze, steel or or member of a viaduct, trestle, or frame bent other metal discs enclosed in the pivot of a serving to distribute the loads upon the columns center bearing swing span to reduce the fric- and to hold them in their proper relative posi- tional resistance in the operation of the span. tions. The topmost piece or member of a pile bent in Center Lock. A locking device that transmits a viaduct or trestle serving to distribute the shear at the centerline of a double leaf bascule loads upon the piles and to hold them in their or double swing span bridge. This eliminates proper relative positions. See PIER CAP and deflection and vibration at the center of the PILE CAP. span. Capillary Action. The process by which water is Center Wedges. On a swing bridge, the assem- drawn from a wet area to a dry area through bly of pedestals and wedges located upon the the pores of a material. pivot pier beneath the loading girder and oper- Capstone. 1. The topmost stone of a masonry ated mechanically to receive the pivot pier live pillar, column or other structure requiring the loads and transmit them direct to the substruc- use of a single capping element. 2. One of the ture, thus relieving the pivot casting from all, stones used in the construction of a stone para- or nearly all, live load stress. pet to make up its topmost or "weather" course. Centering.The supportingstructureupon Commonly this course proj ects on both the in- which the arch ring is constructed. This com- side and outside beyond the general surface of monly consists of timber or metal framework the courses below it. having its topmost portion shaped to conform Carnegie Beam. See WIDE FLANGE. with the arch intrados and finished by covering with lagging or with bolsters, the latter being Catch Basin. A receptacle, commonly box- spaced to permit treatment of the mortared shaped and fitted with a grilled inlet and a pipe joints of stone masonry. outlet drain designed to collect the rain water Support for formwork for any slab, beam, or and floating debris from the roadway surface other generally horizontal concrete structure. and retain the solid material so that it may be removed at intervals. Catch basins are usually Centering Device. The mechanical arrange- installed beneath the bridge floor or within the ment or device which guides the span of a bas- approach roadway with the grilled inlet adja- cule or a vertical lift span to its correct location cent to the roadway curb. upon its supports when being moved from open to closed position. Catchment Area. See DRAINAGE AREA. 'Catwalk. A narrow walkway for access to some Channel Profile. Longitudinal section of a chan- part of a structure. nel. Cement Paste. Theplasticcombinationof Chase. A channel, groove or elongated recess cement and water that supplies the cementing built into a structure surface for 1) the recep- action in concrete. tion of a part forming a joint or (2) the installation of a member or part of the structure. Cement Matrix. The binding medium in a mortar or concrete produced by the hardening of Check Analysis. See LADLE ANALYSIS.

G-9 Chord. In a truss, the upper and the lower lon- minor irregularities. Among shop and field gitudinal members, extending the full length workers this condition is sometimes described and carrying the tensile and compressive forces as "the go and come" or "the play" allowance. which form the internal resisting moment, are termed chords. The upper portion is designated Clear Headway. (Headway.) The vertical clear- the upper, or top, chord and correspondingly ance beneath a bridge structure available for the lower portion is designated the lower, or bot- the use of navigation. See CLEARANCE. In tom, chord. The chords may be paralleled, or the tidal waters headway iS measured above mean upper one may be polygonal or curved (arched ) 'high tide elevation. and the lower one horizontal, or both may be Clear Span. The unobstructed space or distance polygonal. In general, the panel points of poly- between the substructure elements measured, gonal top chords are designed to follow the arc by common practice, between faces of abut- of a parabola and are, therefore, truly parabolic ments and/or piers. However, when a structure chords. :"olygonal shaped chords are commonly is located upon a stream, river, tidal. inlet or described as "broken chords." other waterway used by navigation, the clear span dimension is measured at mean low water Chord Members. Trusses are commonly di- elevation and may be the distance between vided lengthwise into panels, the length of each guard or fender piers, dolphins or other con- being termed a panel length. The corresponding structions for the protection of navigation. members of the chords are described as upper, or top, chord members and lower, or bottom, Clevis. A forked device used to connect the end chord members. of a rod upon 1a gusset plate or other structural part by means of a pin. It commonly consists of Clearance. The unobstructed space provided : a forging having a forked end arranged to form (1) in a through or half-through truss or a two eyes or eyelets for engaging a pin and a through plate girder type bridge, and (2) upon nut-like portion, constructed integrally there- a deck truss or girder type bridge for the free with, for engaging the correspondingly threaded passage of vehicular and pedestrian traffic. end of a rod. However, the forked end (cievis) Clearance is measured in vertical and horizon- may form an integral portion of a rod without tal (lateral) dimensions and may or may not be provision for adjustment of its length. An ad- determined or regulated by standard (clearance justable member having a fixed clevis at one diagram) requirements. Vertical clearance for end may be fitted with a thread and nut at its vehicles is measured above the elevation of the opposite end while one having fixed clevises at floor surface at its crown dimension while hori- its ends may be fitted with either a sleeve nut or zontal clearance is commonly measured from or a turnbuckle in its midlength portion. Lateral with reference to the edge of travelway. bracing and tie-rod diagonals onoldsteel The unobstructed space provided below a trusses often use devises. bridge superstructure for (1) the passage of a Clevis Bar. A member consisting of a rod river or stream with its surface burden of float- having upset threaded ends fitted with clevises ing debris; (2) the passage of navigation craft for engaging end connection pins. To render a commonly designated "clear headway" and (3) clevis bar adjustable after assembling in a the passage of vehicular and pedestrian traffic. structure its ends are right and left threaded, This form of clearance is frequently designated or it may be constructed with a sleeve nut or a "under-clearance" to differentiate it from the turnbuckle within its length, the end threads provision for the requirements of the transpor- upon each of its sections being right and left tation service supported by the structure. hand and its devises forged integrally with the The sp.cr; tillowed for (1) the tolerance per- body sections of the bar. mitted in the dimensions of structural shapes ; (2) the free assembling and adjustment of the Clip Angle. See CONNECTION ANGLE. elements of members or the members of a struc- Coefficient of Thermal Expansion. Theunit ture; and (3) the variations in dimensions inci- strain produced in a material by a change of dent to workmanship, temperature changes and one degree in temperature.

G--10 Cofferdam. In general, an open box-like struc- Concrete. A composite material consisting es- ture constructed to surround the area to be sentially of a binding medium within which are occupied by an abutment, pier, retaining wall or embedded particles or fragments of a relatively ether structure and permit unwatering of the inert mineral filler. In portland cement con- enclosure so that the excavation for the prepa- crete, the binder or matrix, either 3n the plastic ration of a foundation and the abutment, pier, or the hardened state, is a combination of port- or other construction may be effected in the land cement and water. The filler material, open air. In its simplest form, the dam consists called aggregate, is ..'ly graded in size of interlocking steel sheet piles. See SHEET from fine sand to pebbles or :tones which may, PILE COFFERDAM. in some concrete, be soveral inches in diameter. Collision Strut. A redundant member intended Concrete is used in conjunction with stone to reinforce the inclined .end post of a through fragments or boulders, of "one man" size or truss against damage from vehicular traffic. It larger, imbedded therein to produce "cyclo- joins the end post at a height above the road- pean" or "rubble" concrete. way conceived to be the location of collision Connection Angle. (Clip Angle.) A piece or contact and, commonly, connects it with the pieces of angle serving to connect two elements first interior bottom chord panel point. The use of a member or two members of a structure. of collision struts in highway bridges is limited. Consolidation. The .; ime-dependent change in Cold Work. The forming, such as rolling or volume of a soil mass under compressive load bending, of a material at ordinary room tem- caused by pore-water slowly escaping from the perature. Also applied to such deformation of pores or voids of the soil. The soil skeleton is steel elements in service under concentrated unable to support the load by itself and changes forces. structure, reducing its volume and usually producing vertical settlements. Column. A general term applying to a member resisting compressive stresses and having, in Continuous Girder. A general term applied to a general, a considerable length in comparison beam or girder constructed continuously over with its transverse dimensions. This term is one or more intermediate supports. sometimes used synonymously for "post." Continuous Spans. A beam, girder, or truss A member loaded primarily in compression. type superstructure designed to extend continu- See also STRUT, POST, PILLAR. ously over one or more intermediate supports. Composite Joint. A joint in which the strength, Continuous Truss. A truss having its chord and rigidity or other requisites of its function are web members arranged to continue uninter- developed by combined mechanical devices, or ruptedly over one or more intermediate points by a fusion weld in conjunction with one or of support, i.e., having three or more points of more mechanical means or appliances. The un- support. certain functioning of joints of this type makes their use undesirable. Continuous Weld. A weld extending throughout the entire length of a joint. Compound Roller. A roller consisting of a large Coping. A course of stone laid with a projection solid cylinder at the center surrounded by a beyond the general surface of the masonry nest of smaller solid rollers having circular below it and forming the topmost portion of a spacing bars engaging their ends and enveloped retaining wall, pier, abutment, wingwall, etc. In in a large hollow cylinder which forms the exte- general, the top surface is battered (washed) to rior surface of the assemblage. The large roller prevent accumulation of rain or other moisture is commonly bored throughout its length at its thereon. center to permit observation of its interior material. A course of stone capping the curved or V- shaped extremity of a pier, providing a transi- Compression (inelastic). Compression beyond tion to the pier head proper. When so used it is the yield point. commonly termed the "starling coping," "nose

G-11 coping," the "cut-water coping" or the "pier ex- Counterfort. A bracket-likewallprojecting tension coping." from another wall, to which it adds stability by In concrete construction the above terms are being integrally built with or otherwise se- used without change. curely attached to the side to which external forces are applied tending to overturn it. A Corbel. A piece or part constructed to project counterfort, as opposed to a buttress, acts en- from the surface of a wall, column or other por- tirely to resist tensile and bending stresses. It tion of a structure to serve as a support for a may extend from the base either part or all the brace, short, beam or other member. way to the top of the wall it is designed to rein- A projecting course or portion of masonry force. serving : (1) as a support for a superimposed Counterforted Wall. See RETAINING member or members of a structure, or (2) as a WALL. part of the architectural treatment of a structure. In stone and brick masonry construction, Counterweight. A weight placed in position so this form of corbel is termed a "corbol course" as to counter balance the weight of a movable implying greater length than that of a simple part (such as bascule leaf or vertical lift span). corbel. Counterweight Well. (Tail Pit.) The enclosed Corrosion. The general disintegration and wast- space located beneath the bridge floor at the ing of surface metal or other material through approach end to accommodate the counter- oxidation,decomposition,temperature,and weight and its supporting frame during the other natural agencies. opening-closing cycle of the movable span of certain types of bascule bridge structures. Corrosion(electrolytic).Corrosionresulting from galvanic action. Course. In stone masonry, a layer of stone composed of either cut or uncut pieces laid with Cotter Bolt. A bolt having a head at one end horizontal or slightly longitudinally inclined and near the opposite end a round hole or a joints. hexagonal slot fitted with a cotter pin in the former or a tapered wedge in the latter. A In brick masonry, a layer of bricks bedded in cotter pin is usually formed by bending a piece mortar. of half-round rod to form a loop eye and a split Cover. In reinforced concrete, the clear thick- body permitting its end to be splayed, thus hold- ness of concrete between a reiniz.srcing bar and ing it in position while a cotter wedge may be the surface of the concrete. split for the same purpose, but either of these locking devices may be undivided and only bent Cover Plate. A plate used in conjunction with sharply to prevent withdrawal. Cotter boltsare flange angles or other structural shapes to pro- commonly fitted with one or two washers. vide additional flange section upon a girder, A cotter bolt fitted with a key is sometimes column, strut or similar member. termed. a "key bolt." Covered Bridge. An indefinite term applied to a Counter. A truss web member which functions wooden bridge having inits construction a only when the span is partially loaded and shear truss of any type adaptable to its location re- stresses are opposite in sign to the normal con- quirements. To prevent or delay deterioration ditions. The dead load of the truss does not of the timbers through infiltration of moisture stress the counter. See WEB MEMBERS. into the framed or other joints, the entire structure, or instead, only its trusses are covered by Counterbalancing Chain. (Balancing Chain.) a housing consisting of boards and shingles or The chains made a part of the operating equip- other covering materials, fastened upon the side ment of a vertical lift bridge to function as a girts, rafters, purlins, or other parts intended weight counteracting the varying weight of the to receive them. A covered bridge may be either supporting cables incidental to the movements a through or a deck structure. The former may of the span. he constructed with pony trusses. Cracking (reflection). Visible cracks in an over- Cross Wall. See DIAPHRAC WALL. lay indicating cracks in the concrete under- Crown of Roadway. 1. The crest line, of the con- neath. vexed surface. 2. The vertical dimension de- Creep. An inelastic deformation that increases scribing the total amount the surface is con- with time while the stress is constant. vexed or raised from gutter to crest. This is Crib. A structure consisting of a foundation sometimes termed the cross fall of roadway. grillage combined with a superimposed frame- Culvert. A small bridge constructed entirely work providing compartments or coffers which below the elevation of the roadway surface and are filled with gravel, stones, concrete or other having no part or portion integral therewith. material satisfactory for supporting the ma- Structures over 20 feet in span parallel to the sonry or other structure to be placed thereon. roadway are usually called bridges, rather than The exterior portion may be planked or sheet- culverts ;and structures less than 20 feet in piled to protect the crib against damage by ero- span are called culverts even though they sup- sion or floating debris. port traffic loads directly. A structure consisting of a series of box-like compartments built of round or squared tim- Curb. A stone, concrete or wooden barrier par- bers having the crosstimbers (compartment di- alleling the side limit of the roadway to guide vision and end wall timbers) drift bolted and the movement of vehicle wheels and safeguard dove-tail framed or half framed to interlock bridge trusses, railings or other constructions with the side timbers, thus producing a rigid existing outside the roadway limit and also pe- framework of the height desired. A portion of destrian traffic upon sidewalks from collision the compartment is constructed with floors to with vehicles and their loads. serve as ballast boxes for loading and sinking Curb Inlet. See SCUPPER. the crib in its final position after which the remaining compartments are filled or partially Curtain Wall. A term commonly applied to a filled with gravel, stones or other material to thin masonry wall not designed to support su- render the entire structure stable against the perimposed loads either vertically or trans- forces to which it may be subjected. versely. This latter type of crib is used as a protection A thin vertically placed and integrally built against wave action and stream currents pro- portion of the paving slab of a culvert intended ducing scour and erosion adjacent to bridge to protect the culvert against undermining by structures to prevent undermining of abut- stream scour. A similar construction placed in ments and piers or other substructure elements an inclined position is termed an "apron wall" and also to serve as a training wall averting or "apron." changes in shore' and bank locations. A wall uniting the pillar or shaft portions of Cribbing. A construction consisting of wooden, a dumbbell pier. However, its service function metal or reinforced concrete units so assembled is that of a frame composed of struts and as to form an open cellular-like structure for braces rendering the entire structure integral supporting a superimposed load or for resisting in its action. As here applied the term is synon- horizontal or overturning forces acting against ymous with "diaphragm wall." it. Curve Banking. See SUPERELEVATION. Cross Frames. Transverse bracings between two main longitudinal members. See DIA- Curves in Plan and Profile. A roadway may be PHRAGM and BRACING. curved in its lateral alignment, its vertical con- Cross Girder, Transverse Girder. A term ap- tour, or in both alignment and contour combined. The primary curves are described as : plied to large timber members and to metal and reinforced concrete girder-like members placed 1. Horizontal Curve. A curve in the plan loca- generally perpendicular to and connected upon tion defining the alignment. the main girders or trusses of a bridge span. 2. Vertical Curve. A curve in the profile loca- including intermediate and end floor beams. tion defining the elevation.

G-13 Cut. (Cutting.) That portion of a highway, rail- Pecking. A term specifically applied to bridges way, canal, ditch or other artificial construction having wooden floors and used to designate the of similvr character produced by the removal of flooring only.It does not include the floor the natupal formation of earth or rock whether stringers, floor beams, or other members serv- sloped or level. The general terms "side hill cut" ing to support the flooring. and "through cut" are used to describe the resulting cross sections of the excavations com- Deformation (elastic). Deformation occurring monly encountered. when stress in a material is less than the yield point. If the stress is removed, the material will Cut Slope. A term applied to the inclined sur- return to its original shape. face of an approach cut terminating in the ditch or gutter at its base, which in turn serves to Depth of Truss. As applied to trusses having remove accumulations of water from all areas parallel chords and to polygonal trusses having drained into it. a midspan length with parallel chords ; the vertical distance between the centerlines of action Cylinder Pier. See PIER. of the top and bottom chords. Design Load. The loading comprising magni- D tudes and distributions of wheel, axle or other concentrations used in the determination of the Dead Load. A static load due to the weight of stresses, stress distributions and ultimately the the structure itself. cross-sectional areas and compositions of the Dead Man. A general term applied to an an- various pOrtions of a bridge structure. chorage member engaging the end of a stay rod, The design loading or loadings fixed by a cable or other tie-like piece or part. The anchor- specificationarevery commonly composite age member is made secure through the resist- rather than actual, but are predicated upon a ance to movement produced by the earth, stone, study of various types of vehicles. In lieu of a brickbats, or other material used to embed and loading so determined for use as "standard," an cover the anchor piece which may consist of a equivalent uniform load designed to produce wooden log or timber, a metal beam or other resulting structures practically identical with structural shape, a quarried stone boulder or those evolved by the use of such loadings may any other adaptable object. This type of anchor be used. One or more concentrated loads may be member is usedto restrain and hold in position used in conjunction with the uniform load to piles, bulkheads, cribs, and other constructions secure the effect corresponding to the incorpo- against horizontal movement as well as to resist ration of especially heavy vehicles within the the stresses of tie members acting in inclined normally maximum traffic considered as likely and vertical directions. to pass upon a given bridge or a series of Debris Rack. A grill type barrier used to inter- bridges. Such equivalent loadings are merely a cept debris above a sewer or culvert inlet. convenience facilitating design operations.- In rating bridges for the Bridge Inspection Deck. That portion of a bridge which provides Manual, either the H or HS trucks with their direct support for vehicular and pedestrian alternate lane loadings may be used. Or, if de- traffic. The deck may be either a reinforcedcon- sired, the special legal limit trucks ; Type 3, crete slab, timber flooring, a steel plate or grat- Type 3S 2, and Type 3-3, may be used. ing, or the top surface of abutting concrete members or units. While normally distributing Diagonal. See WEB MEMBERS. load to a system of beams and stringers, a deck Diagonal Stay. A cable support in a suspension may also be the main supporting element of a bridge extending diagonally from the tower to bridge, as with a reinforced concrete slab struc- the roadway system to add stiffness to the ture or a laminated timber bridge. structure and diminish the deformations and Deck Bridge. A bridge having its floor elevation undulations resulting from traffic service. at, nearly at or above the elevation of the up- Diaphragm. A reinforcing plate or member permost portion of the superstructure. placed within a member or deck system, respec-

G-14 tively,todistributestressesand improve stream debris against and adjacent to the up- strength and rigidity. See BRACING. strealit side of the abutment. Diaphragm Wall (cross wall). A wall built Dimension Stone. A stone of relatively large di- transversely to the longitudinal centerline ofa mensions, the face surface of which is either spandrel arch serving to tie together and rein- chisel or margin drafted but otherwise rough force the spandrel walls together with provid- and irregular, commonly called either "rock ing a supp3rt for the floor system in conjunc- face" or "quarry face." tion with the spandrel walls: To provide means Stones quarried with the dimensions large for the making of inspections the diaphragms enough to provide cut stones with given finished of an arch span may be provided with man- dimensions. holes. The division ,walls of a reinforced concrete Distribution Girder. A beam orgirder-like caisson dividing its i:terior space into compart- member forming a part of the frame by which ments and reinforcing its walls. A wall serving the dead and live loads are transmitted to the to subdivide a box-like structure or portion of a drum girder of a rim-boaring swing span. structure into two or more compartments, or sections. Ditch. See DRAIN. Dike. (Dyke). An earthen embankment con- Diversion Drain. (Diversion Flume.) An open structed to provide a barrier to the inundation top paved drain constructed for the purpose of of an adjacent area which it encloses entirely or diverting and conveying water from a roadway in part. gutter down the inclined surface of a bridge approach embankment or causeway. When used in conjunction with a bridge, its functions are commonly those of preventing Dolphin. A group or cluster of piles driven in one stream erosion and locr.lized scour and/or to so to two circles about a center pile and drawn direct the stream cip,ent that debris will not together at their top ends around the center pile accumulate upon bottom land adjacent to ap- to form a buffer or guard for the protection of proach embankments. abutments, piers, towers, channel span piers or other portions of a bridge or other portions of the structure. exposed to possible injury by collision with wa- This term is occasionally misapplied to crib terbound traffic. The tops of the piles are served construction used to accomplish a like result. with a wrapping consisting of several plies of See CRIB. wire, rope, coil, twist link, or stud link anchor chain, which, by being fastened at its ends only, Spur Dike. A projecting jetty-like construc- renders itself taut by the adjustments of the tion placed adjacent to an abutment of the "U," piles resulting from service contact with ships, "T," block or arched type upon the upstream barges, or other craft. The center pile may pro- and downstream sides, but sometimes only on ject above the others to serve as a bollard for the upstream side, to secure a gradual contrac- restraining and guiding the movements of wa- tion of the stream width and induce a free even ter-borne traffic units. flow of water adjacent to and beneath a bridge. Single steel and concrete piles of large size They may be constructed in extension of the may also be used as dolphins. wing wall or a winged abutment. The common types of construction used for Double Movable Bridge. A bridge in which the clear span for navigation is produced by joining water wings are: (1) Wooden cribs filled with the arms of two adjacent swing spans or the stones; (2) embankments riprapped on the wa- leaves of two adjacent bascule spans at or near terway side ; and (3) wooden and metal sheet the center of the navigable channel. The arms piling. or leaves may act as cantilevers with a shear Spur dikes serve to prevent stream scour and lock at their junction to provide for the passage undermining of the abutment foundation and to of traffic over the joint. The leaves of bascules relieve the condition which otherwise would may be equipped to act as a hinged arch. Spans tend to gather and hold accumulations of comprised of two bascule leaves are called dou-

G-15 bleleafbasculebridges.See MOVABLE taining walls, counterweight wells or parts of a BRIDGE. bridge or incidental structure. Dowel. A short length of metal bar, either A ditch, drain, gutter, gully, flume, catch round or square, used to attach and prevent basin, downspout, scupper, weep hole, or other movement and displacement of wooden, stone, construction or appliance facilitating the inter- concrete, or metal pieces when placed in a ception and removal of water. bored, drilled, or cored hole located in their Drainage Area, Catchment Area. The area from contact surfaces. A dowel may or may not be which the run-off water passing beneath a sized to provide a driving fit in the hole. In bridge or passing a specific location in a river stone and premolded concrete structures the or stream is produced. dowels are commonly set in lead, mortar, or other material filling the portions of the holes Drawbridge. A general term appliedtoa not occupied by the dowels. In concrete con- bridge over a navigable stream, river, lake, struction the plastic concrete is usually either canal, tidal inlet, gut or strait having a movable placed around a dowel or the dowel is thrust superstructure span of any type permitting the into it. channel to be freed of its obstruction to naviga- In general, dowels function to resist shear tion. A popular but imprecise term. forces, although footing dowels in reinforced Probably the earliest use of a drawbridge concretewalls and columnsresist bending was for military purposes, utilizing a single leaf forces. hinged frame lifted up or let down by a compar- Drain. (Ditch, Gutter.) A trench or trough-like atively simple manually operated mechanism. excavation made to collect water. In general a Draw Rest. A support constructed upon a drain is considered as functioning to collect and fender or guard pier and equipped with a latch convey water whereas a ditch may only serve to block for holding a swing span in open position. collect it. This support may consist of a block of masonry, A gutter is a paved drain commonly con- a rigid metal frame or other construction structed in conjunction with the curbs of the adapted to the service requirements. roadway or instead built closely adjacent to the paved portion of the roadway. Draw Span. A general term applied to either a swing or a retractile type movable superstruc- Drain Hole. (Drip Hole.) An aperture extend- ture span of a bridge over a navigable stream, ing through a wall to provide an egress for river, lake, canal, tidal inlet, gut or strait. See water which might otherwise accumulate upon MOVABLE BRIDGE. one of its sides. In this connection the term "weep hole" and "drain hole" are commonly Drift Bolt. A short length of metal bar, either used. See WEEP HOLE. round or square, used to connect and hold in A cored, punched or bored hole in a box or position wooden members placed in contact. It trough shaped member or part toprovide may or may not be made with a head and a. means for the egress of accumulated water or tapered point. Drift bolts are commonly driven other liquid matter. In areas exposed to freez- in holes having a diameter slightly less than the ing temperatures, these holes are used to pre- bolts. This condition appears to be the recog- vent damage by the expansive force incident to nized practical difference between a drift bolt the freezing of water accumulations. and a dowel. The difference is more a matter of usage of terms rather than of functions to be Drainage. The interception and removal of performed. water from the roadway and/or sidewalk surfaces of a bridge or its .approaches; from be- Drip Bead. A channel or groove in the under neath the paved or otherwise prepared roadway side of a belt course, coping, or other protrud- and/or sidewalk surfaces of the approaches and ing exposed portion of a masonry structure in- from the sloped surfACes of hillsides, cuts, em- tended to arrest the downward flow of rain bankments, and causeways ; from the backfill or water and cause it to drip off free from contact other material in contact with abutments, re- with surfaces below the projection.

G-16 Drip Hole. See DRAIN HOLE. resulting from the deflections and vibrations set Drop Inlet. A box-like construction commonly up by the movements of traffic upon a swing built integrally with the upstream end of a cul- span when the lifting device is impsroperly ad- vert with provision for the water to flow in at j usted. its top and to enter the culvert proper at its End Lift. The mechanism consisting of wedges, bottom or within its bottom portion. Vegetable toggles, link-and-roller, rock,z-and-eccentric or or other material likely to become lodged in the other devices combined with shafts, gears, or culvert may be retained in the base portion of other operating parts requisite to remove the this receiving device by constructing its base to camber or "droop" of a swing span. form a sump below the inlet elevation of the culvert. The culvert inlet may or may not be End Post. The end compression member of a provided with a grating. truss, either vertical or inclined in position and extending from chord to chord, functioning to Drum Girder. (Rim Girder.) The circular plate transmit the truss end shear to its end bearing. girder forming a part of a swing bridge turnta- ble transferring its loadings to the rollers and Epoxy. A synthetic resin which cures or hard- to the circular track upon which they travel. ens by chemical reaction between components When the swing span is in "closed" position the which are mixed together shortly before use. drum girder track receives the superstructure dead and live loads and transmits these to the Equalizer. A balance lever engaging the coun- substructure bearing area beneath the track. terweight and the suspending cables of a vertical lift span as a means of a',.ijurtment and Ductility. The ability to withstand non-elastic equalization of the stresses in the latter. deformation without rupture. Equilibrium. In statics, the condition in which Dyke. See DIKE. the forces acting upon a body are such that no external effect (or movement) is produced. E Efflorescence. A white deposit on concrete or Equivalent Uniform Load. A load having a con- brick caused by crystallization of soluble salts stant intensity per unit of its length producing brought to the surface by moisture in the ma- an effect equal or practically equal to that of a sonry. live load consisting of vehicle axle or wheel concentrations spaced at varying distances apart, Elastic Deformation. See DEFORMATION. when used as a substitute for the latter in de- Elastomer. A natural or synthetic rubber-like termining the stresses in a structure. material. Expansion Bearing. A general term applied to a Electrolytic Corrosion. See CORROSION device or assemblage designed to transmit a re- (ELECTROLYTIC). action from one member or part of a structure to another and to permit the longitudinal move- Element. Metal Structures. An angle, beam, ments resulting from temperature changes and plate or other rolled, forged or cast piece of superimposed loads without transmitting a hor- metal forming a part of a built piece. For izontal force to the substructure. Wooden Structures. A board, plank, joist, scan- The expansion bearing is designed to permit tling or other fabricated piece forming a part of movement by overcoming sliding,rolling or a built piece. other friction conditions. In general, provision End Block. On a prestressed concrete beam, the is made for a movement equal to 11,4" in 100', thickening of the web or increase in beam width thus providing for ordinary irregularities in at the end to provide adequate anchorage bear- field erection and adjustment. ing for the post-tensioning wires,rods, or strands. Expansion Dam. The part of an expansion joint serving as an end form for the placing of con- End Hammer. The hammering action of an end crete at a joint. Also applied to the expansion lift device upon its pedestal or bearing plate joint device itself.

G-17 Expansion Joint. A joint designed to provide axis or axes. 2. The curve defining the exterior means for expansion and contraction move- surface of an arch. ments produced by temperature changes, load- Eyebar. A member consisting of a rectangular ings or other agencies. bar body with enlarged forged ends or heads Expansion Rocker. An articulated assemblage having holes through them for engaging conforming a part of the movable end of a girder necting pins. or truss and facilitating the longitudinal move- An adjustable eyebar is composed of two sec- ments resulting from temperature changes and tions fitted with upset threaded ends engaging a superimposedloads. Apart fromitshinge sleevenut or a turnbuckle. connection the rocker proper is a cast or built- up member consisting essentially of a circular Eyebolt. (Ringbolt.) A bolt having a forged eye segment integrally joined by a web-like portion at one end used, when installed in a structure, to a hub fitted for hinge action either with a pin to provide means for making fast the end of a hole or by having its ends formed into trun- cable, a hooked rod or other part or portion of nions. In its service operation the rocker is com- the bidge, or instead to provide a means of monly supported upon a shoe plate or pedestal. anchorage for unrelated equipment or struc- Strictly speakir is is a segment of a roller. tures. A short cast o' rp member hinged at both A ringbolt is essentially an eyebolt fitted with ends, or instea 3 at one end and provided a ring to serve the same purpose as described with a circular . nt or spherical type bear- above for an eyebolt with added articulation. ing at the other to facilitate expansion and contraction on other longitudinal rotational move- F ments. Face Stones. The stones exposed to view in the Expansion Roller. A cylinder so mounted that face surfaces of abutments, piers, arches, re- by revolution it facilitates expansion, contrac- taining walls or other stone structures. tion or other movements resulting from temperature changes, loadings or other agencies. Face Wall. Expansion Shoe. (Expansion Pedestal.) An ex- Abutment. See BREAST WALL. pansion bearing member or assemblage de- Spandrel ArchStructure. The outermost signed to provide means for expansion and con- spandrel walls providing the face surfaces of traction or other longitudinal movements. In thecompletedstructure.See SPANDREL general, the term "shoe" is applied to an assem- ARCH. blage of structural plates or plate-like castings Factor of Safety. A factor or allowance predi- permitting movement by sliding while the term cated by common engineering practice upon the "pedestal" is used to describe assemblages of failure stress or stresses assumed to exist in a castings or built-up members securing a some- structure or a member or part thereof. Its pur- what greater total depth and providing for pose is to provide a margin in the strength, rig- movement either by sliding or by rolling. idity, deformation and endurance of a structure The masonry plate or casting is commonly or its component parts compensating for irreg- held in a fixed position by anchor bolts and the ularities existing in structural materials and superimposed shoe plate or pedestal is free to workmanship, uncertainties involved in mathe- move longitudinally upon it or upon intervening matical analysis and stress distribution, service rollers but is restrained from transverse move- deterioration and other unevaluated conditions. ment either by a rib and slot, by pintles, by anchorage or by anchorage in combination with Falsework. A temporary wooden or metal one of the first two mentioned. The term "bed framework built to support without appreciable plate" is sometimes used to designate the bot- settlement and deformation the weight of a tom portion of the assemblage. structure during the period of its construction and until it becomes self-supporting. In general, Extrados. (Back.) 1. The curved surface of an the arrangement of' its details are devised to arch farthest from its longitudinal construction facilitate the construction operations and pro-

.G-18 vide for economical removal and the salvaging contour of an area, or for constructing an em- of material suitable for reuse. bankment. Fascia. An outside, covering member designed Filler (Filler Plate). In wooden and structural on the basis of architectural effect rather than steel construction. A piece used primarily to fill strength and rigidity although its function may a space beneath a batten, splice plate, gusset, involve both. connection angle, stiffener or other element. A light, stringer-like member spanning longi- Filler Metal. Metal prepared in wire, rod, elec- tudinally between cantilever brackets which trode or other adaptable form to be fused with support large overhangs on girder or beam the structure metal in the formation of a weld. bridges. Filler Plate. See FILLER. Fascia Girder. As exposed outermost girder of a span sometimes treated architecturally or oth- Fillet. 1. A curved portion forming a junction erwise to piovide an attractive appearance. of two surfaces which would otherwise intersect at an angle. 2. In metal castings and rolled Fatigue. The tendency of a member to fail at a structural shapes a fillet is used to disseminate lower stress when subjected to cyclical loading and relieve the shrinkage or other stresses tend- than when subjected to static loading. ing to overstress and, perhaps, rupture the Fe lloe Guard. See WHEEL GUARD. junction material. In castings it may also provide means for movement to take place at Fender. 1. A structure placed at an upstream locations where the rigidity of the mold would location adjacent to a pier to protect it from the otherwise resist and obstruct this action. 3. In striking force, impact and shock of floating concrete construction the use of mitered fillets stream debris, ice floes, etc. This structure is in internal corners of forms not only serves the sometimes termed an "ice guard" in latitudes purposes applying to castings but also facili- productive of lake and river ice to form ice tates both the placing of concrete and the subse- flows. 2. A structure commonly consisting of quent removal of forms. dolphins, capped and braced rows of piles or of wooden cribs either entirely or partially filled Fillet Weld. A weld joining intersecting mem- with rock ballast, constructed upstream and bers by depositing weld metal to form a near- downstream from the center and end piers (or triangular or fillet shaped junction of the sur- abutments) of a fixed or movable superstruc- faces of the members so joined. This weld ture span to fend off water-borne traffic from serves to unite the intersecting surfaces of two collision with these substructure parts, and in elements of a member. the case of a swing span, with the span while in Filling. See FILL. its open position. Finger Dam. Expansion joint in which the Fender Pier. A pier-like structure which per- opening is spanned by meshing steel fingers or forms the same service as a fender but is gener- teeth. ally more substantially built. These structures may be constructed entirely or in part of stone Fish Belly. A term applied to a girder or a truss or concrete masonry. See GUARD PIER. having its bottom flange or its bottom chord, as the case may be, constructed either haunched or Field Coat. A coat of paint applied upon the bow-shaped with the convexity downward. See priming or base coat or upon a coat subse- LENTICULAR TRUSS. quently applied and, generally, after the structure is assembled and its joints completely con- Fixed-Ended Arch. See VOUSSOIR ARCH. nected by bolts, rivets or welds. This applica- Fixed Bearing. The plates, pedestals, or other tion is quite commonly a part of the field erec- devices designed to receive and transmit to the tion procedure and is, therefore, termed field substructure or to another supporting member painting. or structure the reaction stresses of a beam, Fill. (Filling.) Material, usually earth, used for slab, girder, truss, arch or other type of super- the purpose of raising or changing the surface structure span.

G-19 The fixed bearing is considered as holding the Floor System. The complete framework of so-termed "fixed end" of the structure rigidly in floor beams and stringers or other members position, but in practice the clearance space supporting the bridge floor proper and the commonly provided in the anchorage may per- traffic loading including impact thereon. mit a relatively small amount of movement. Flow Line. The surface of a watercourse. Fixed Bridge. A bridge having its superstructure spans fixed in position except that provi- Flux. A material which prevents, dissolves, and sion may be made in their construction for ex- removes oxides from metal during the welding pansion and contraction movements resulting process. It may be in the coating on a metal from temperature changes, loadings, or other stick electrode or a granular mass covering the agencies. arc in submerged arc welding and protects the weld from oxidation during the fusionprocess. Fixed Span. A superstructure span having its position practically immovable, as compared to Footbridge. (Pedestrian Bridge.) A bridge de- a movable span. signed and constructed to providemeans of traverse for pedestrian traffic only. Flange. The part of a rolled I-shaped beam or of a built-upgirder extending transversely Footing.(Footing Course, Plinth.) The en- across the top and bottom edges of the web. The larged, or spread-out, lower portion ofa sub- flanges are considered to carry the compressive structure, which distributes the structure load and tensile forces that comprise the internal re- either to the earth or to supporting piles. The sisting moment of the beam, and may consist of most common footing is the concrete slab, al- angles, plates, or both. though stone piers also utilize footings. Plinth refers to stone work as a rule. "Footer" isa Flange Angle. An angle used to form a flange local term for footing. element of a built-up girder, column, strut or similar member. Foot Wall. See TOE WALL. Floating Bridge. In general this term means the Forms. (Form Work, Lagging, Shuttering.) same as "Pontoon Bridge." However, its parts The constructions, either wooden or metal, providing buoyancy and supporting power may providing means for receiving, molding and consist of logs or squared timbers, held in posi- sustaining in position the plastic mass of con- tion by lashing pieces, chains or ropes, and crete placed therein to the dimensions, outlines floored over with planks, or the bridge itself and details of surfaces planned for its integral may be of hollow cellular construction. parts throughout its period of induration or hardening. Floating Foundation. A term sometimes applied The terms "forms" and "form work" are to a "foundation raft" or "foundation grillage." synonymous. The term "lagging" is commonly Used to describe a soil-supported raft or mat applied to the surface shaping areas of forms foundation with low bearing pressures. producing the intradoses of arches or other Flood Gate. (Tide Gate.) An automaticallyop- curved surfaces, especially when strips are used. erated gate installed in a culvert or bridgewa- Forms. (SIP, Stay-in-Place.) A prefabricated terway to prevent the ingres.3 of flood or tide metal concrete deck form that will remain in water to the area drained by the structure. place after the concrete has set. Floor. See DECK. Form Work. See FORMS. Floor Beam. A beam or girder located trans- Foundation. Thesupporting material upon versely to the general alignment of the bridge which the substructure portion of a bridge is and having its ends framed upon the columns of placed. A foundation is "natural" when consist- bents and towers or upon the trusses or girders ing of natural earth, rock or near-rock material of superstructure spans, A floor beam at the having stability adequate to support the super- extreme end of a girder or truss span iscom- imposed loads without lateral displacementor monly termed an end floor beam. compaction entailing appreciable settlement or

G-20 deformation. Also, applied in an imprecise fash- Frame. A structure having its parts or mem- ion to a substructure unit. bers so arranged and secured that the entire assemblage may not be distorted when support- Consolidated Soil Foundation. A foundation of ing the loads, forces, and physical pressures soft soil rendered more resistant to its loads by considered in its design. The framing of a truss (1) consolidating the natural material, (2) by relates to the design and fabrication of the joint the incorporation of other soil material (sand, assemblages. gravel, etc.) into the soft material, and (3) by the injection of cementing materials into the Framing. The arrangement and manner of join- soil mass which will produce consolidation by ing the component members of a bent, tower, lapidification. truss, floor system or other portion of a bridge structure to insure a condition wherein each ele- Pile or Piled Foundation. A foundation rein- ment and member may function in accord with. forced by driving piles in sufficient number and the conditions attending its design. Framing to a depth adequate to develop the bearing must be interpreted as including both design power required to support the foundation load. and fabrication for the complete structure. Foundation Excavation. (Foundation Pit.) The Friction Roller. A roller placed between parts excavation made to accommodate a foundation or members intended to facilitate change in for a retaining wall, abutment, pier or other their relative positions by reducing the fric- structure or element thereof. tional resistance to translation movement. Foundation Grillage. A construction consisting Frost Heave. The upward movement of and of steel, timber, or concrete members placed in force exerted by soil due to alternate freezing layers. Each layer is normal to those above and and thawing of retained moisture. below it and the members within a layer are Frost Line. The depth to which soil may be generally parallel, producing a crib or grid-like frozen. effect. Grillages are. usually placed under very heavy concentrated loads. G Foundation Load. The load resulting from traffic, superstructure, substructure, approach Galvanic Action. Electrical current between two embankment, approach causeway, or other inci- unlike metals. dental load increment imposed upon a given Gauge. The distance between parallel lines of foundation area. rails, rivet holes, etc. A measure of thickness of sheet metal or wire. Foundation Pile. A pile, whether :-)f wood, reinforced concrete, or metal used to reinforce a Girder. A flexural member which is the main or foundation and render it satisfactory for the primary support for the structure, and which supporting of superimposed, loads. usually receives loads from floor beams and stringers. Foundation Pit. See FOUNDATION EXCA- Any large beam, especially if built up. VATION. Girder Bridge. A bridge whose superstructure Foundation Seal. A mass of concrete placed un- consists of two or more girders supporting a derwater within a cofferdam for the base por- separate floor system of, slab and floor beams, or tion of an abutment, pier, retaining wall or slab, stringer, and floor beam, as differentiated other structure to close or seal the cofferdam from a multi-beam bridge or a slab bridge. againstincomingwaterfromfoundation Any bridge utilizinglarge,built-upsteel springs, fissures, joints or other water carrying beams, prestressed concrete beams, or concrete channels. See TREMIE. box girders. Foundation Stone. The stone or one of the With reference to the vertical location of the stones of a course having contact with the foun- floor system, plate girder spans are divided into dation of a structure. two types, viz.:

G-21 1. Through bridges having the floor system masonry bridge seat, skewback or other sub- near theelevationofthe bottomflanges, structure support to insure a satisfactory dis- whereby traffic passer between the top flanges. tribution of the loads transmitted by the super- 2. Deck bridges having the floor system at or structure shoes, pedestals,or other bearing above the elevation of the top flanges whereby members. traffic passes above the girders. Grout. A mortar having a sufficient water con- Girder Span. A span in which the major longi- tent to render it a free-flowing mass, used for tudinal supporting members are girders. It may filling(grouting)theinterstitial spaces be- be simple, cantilever or continuous in type. tweenthestonesorthestone fragments (spalls) used in the "backing" portion of stone Gothic Arch. (Pointed Arch.) An arch in which masonry; for fixing anchor bolts and for filling the intrados surface is composed of two equal cored spaces in castings, masonry, or other cylinder segments intersecting obtusely at the spaces where water may accumulate. crown. This Tudor Arch is a modification of the Guard Pier. (Fender Pier.) A pier-like struc- Gothic, produced by the introduction of shorter ture built at right angles with the alignment of radius cylinder segments at the haunches thus a bridge or at an angle therewith conforming to rendering It a four-centered form or type. the flow of the stream current and having adequate length, width, and other provisions to Grade Crossing. A term applicable to an in- protect the swing span in its open position tersection of two or more highways, two rail- from collision with passing vessels or other roads or one railroad and one highway at a water-borne equipment and materials. It also common grade or elevation ;now commonly serves to protect the supporting center pier of accepted as meaning the last of these combina- the swing span from injury and may or may not tions. be equipped with a rest pier upon which the Grade Intersection. The location where a hori- swing span in its open position may be latched. zontal and an inclined length of roadway or, The type of construction varies with navigation instead, two inclined lengths meet in profile. To and stream conditions from a simple pile and provide an easy transition from one to the other timber structure or a wooden crib-stone bal- they are connected by a vertical curve and the lasted structure t,o a solid masonry one, or to a resulting profile is a sag or a summit depending combination construction. In locations where upon whether concaved or convexed upward. ice floes or other water-borne materials may accumulate upon the upstream pier end, a Grade Separation. A term applied to the use of cutwater or a starling is an essential detail. See a bridge structure and its approaches to divide FENDER PIER. or separate the crossing movement of vehicular, pedestrian or other traffic, by confining portions Guard Railing.(Guard Rail, Guard Fence, thereof to different elevations. See OVERPASS. Protection Railing.) A fencelike barrier or protection built within the roadway shoulder Gradient. The rate of inclination of the road- area and intended to function' as a combined way and/or sidewalk surface(s) from horizon- guide or guard for the movement of vehicular tal applying to a bridge and its approaches. It is and/or pedestrian traffic and to prevent or commonly expressed as a percentage relation of hinder the accidental passage of such traffic be- horizontal to vertical dimensions. yond the berm line of the roadway. Gravity Wall. See RETAINING WALL. Guide. A member or element of a member func- Grillage. A platform-like construction or assem- tioning to hold in position and direct the move- blage used to insure distribution of loads upon ment of a moving part. unconsolidated soil material. See FOUNDA- Guide Roller. A roller fixed in its location or TION GRILLAGE. position and serving both as a friction roller A frame composed of I-beams or other struc- and as a pilot or guide for a part or member in tural shapes rigidly connected and built into a contact with it.

G-22 Gusset. A plate serving to connect or unite the vanishing towards or at the center. The curve elements of a member or the members of LI of the lower flange or surface may be circular, structure and to hold them in correct alignment elliptic, parabolic, straight or stepped. and/or position at a joint. A plate may function Head. A measure of water pressure expressed both as a gusset and Mice plate while under in terms of an equivalent weight or pressure other conditions it may function as a gusset and exerted by a column of water. The height of the stay plate. See SPLICE PLATE and STAY equivalent column of water is the head. PLATE. Headwater. The depth of water at the inlet end Gutter. See DRAIN. of a pipe, culvert, or bridge waterway. Gutter Grating. A perforated or barred cover Headway. See CLEAR HEADWAY. placed upon an inlet to a drain to prevent the entrance of debris gathered and brought to the Heat Treatment. Any of a number of various inlet by the water stream. operations involving heating and cooling that are used to impart specific properties to metals. Guy. A cable, chain, rod or rope member serv- Examples are tempering, quenching, annealing, ing to check and control undulating, swaying or etc. other movements, or to hold a fixed alignment or position a structure or part thereof by hav- Heel of Span. The rotation end of a bascule ing one of its ends bolted, clamped, tied or oth- span. erwise fastened upon it, the other end being se- Heel Stay. See SHEAR LOCK. cured upon a part or member of the structure Hemispherical Bearing. A bearing which uti- or upon a disconnected anchorage. lizes the ball and socket principle by having male and female spherical segments forming H the bearing areas or surfaces of the interlock- H-Beam. (H-Pile.) A rolled steel bearing pile ing elements, thus providing for movements by having an H-shaped cross section. revolution in any direction. In order to insure accurate adjustment of the Hand Hole. Holes provided in cover plates of mating elements it is essential that a pintle or built-up box sections to permit access to the in- other self-centering device be provided as a part terim: for maintenance and construction pur- of the construction details. poses. Hinged Joint. A joint constructed with a pin, Hand Operated Span. A manpower-operated cylinder segment, spherical segment or other movable span to which the force for operating device permitting movement by rotation. is applied upon a capstan, winch, windlass or wheel. Hip Joint. (The Hip of Truss.) The juncture The terms "Hand Draw Bridge," "Hand of the inclined end post with the end top chord Swing Bridge" and "Lever Swing Bridge" are member of a truss. In the truss of a swing span, applied to swing spans of hand-operated type. the juncture of the inclined end post located adjacent to the center of span, with the com- Hand :tail. See RAILING. bined top chord and the connecting tie member Hanger. A tension element or member serving between the swing span arms, is designated an to suspend or support a member attached there- "interior hip joint" or an "interior hip of to. A tension member, whether a rod, eyebar, truss." o;. built-up member supporting a portion of the Hip Vertical. The verticallyplaced tension floor system of a truss, arch or suspension span. member engaging the hip joint of a truss and In suspension bridge construction wire cable is supporting thefirst panel floor beam in a used and the complete member is commonly through truss span, or instead, only the bottom termed a "suspender." chord in a deck truss span. Haunch. A deepening of a beam or column, the Hook Bolt. 1. A bolt having a forged hook at depth usually being greatest at the support and one end used for essentially the same purposes

G-23 as described for an eyebolt. See EYEBOLT. 2. vent displacement they will be, in general, rig- A bolt having its head end bent ator nearly at a idly fixed upon the structure. However, certain right angle with its body portion and, when in types of structures are adapted to the use of use, acting as a clamp. movable platform devices for suspension from Howe Truss. A truss of the parallel chord type the railings or other parts which are or may be originally adapted to wooden bridge construc- adapted thereto. tion but with the later development of metal The term "catwalk" is applied to narrow per- bridge trusses it was adopted only to a limited manent walks supported, usually, by brackets extent due to the uneconomicaluse of metal in or by hangers and located below and/or above its compression members. The web system is the bridge floor. This term is also applied to composed of vertical (tension) rods at the panel temporary walks used in the construction of points with an X pattern of diagonals. suspension and other types of bridges as utilities facilitating the movements of labor and ma- Hydrolysis. A chemicalprocess of decomposi- terials, and the supervision and inspection oper- tion in the presence of elements of water. ations. Hydroplaning. Loss of contact betweena tire Intercepting Ditch. A ditch constructed to pre- and the deck surface when the tire planesor vent surface water from flowing in contact with glides on a film of water covering the deck. the toe of an embankment or causeway or down the slope of a cut. Intergranular Pressure. Pressure between soil grains. Ice Guard. See FENDER. Intermittent Weld. A noncontinuous well com- Impact. As applied to bridge designa dynamic monly composed of a series of short welds with increment of stress equivalent in magnitude to intervening spaces arranged with fixed spacing the difference between the stresses producedby and length. a static load when quiescent and by a load moving in a straight line. Intrados. (Soffit.) The curved surface of an arch nearest its longitudinal (constructional) Impact Load. (Impact Allowance.) A load al- axis or axes. Properly spee.king the intrados is lowance or increment intended to provide for the the curve defining the interior surface of the dynamic effect of a load applied ina manner arch. other than statically. Indeterminate Stress. A stress induced bythe incorporation of a redundant member ina truss or of an additional reaction in a beam rendering Jack Stringer. The outermost stringer support- stress distributions indeterminate by the princi- ing the bridge floor in a panel or bay. It is com- ples 'o'f statics. monly of less strength than a main stringer. In redundant beamsor trusses the distribu- Joint. In Stone Masonry. The space between in- tion of the stresses dependsupon the relative dividual stones. stiffnesses or areas of the members. In Concrete Construction. The divisions or Inelastic Compression.See COMPRESSION terminations of continuity produced at predeter- (INELASTIC). mined locations or by the completion of a period Inspection Ladders. (Inspection Platforms and of construction operations. These may or may Walks.) Special devices or appliances designed not be open. to afford a safe and efficient means for making In a Truss or Frame Structure. (1) A point at inspections and tests to determine the physical which members of a truss or frame are joined, condition of a structure and to facilitate repair (2) the composite assemblage o-.! pieces or mem- operations incident to its maintenance which bers around or about the poiiit of intersection must include these service conveniences. Topre- of their lines of action in a truss or frame.

G-24 K sion member permitting free longitudinalmove- Keystone. A stone of the crown string course of ment of the anchorage chain at locations where an arch. However, this term is most commonly it changes is direction and providing for elastic applied to the symmetrically shaped wedge- deformations induced by temperature changes like stone located in a head ring course at the and the pull exerted by the suspension member. crown of the arch, which thus exposed to view produces desired architecturaleffects.This L head ring stone commonly extends short dis- Lacing. See LATTICE. tances above and below the extradosal and intradosal limits of the voussoirs of adjoining Ladle Analysis. (Ladle Test, Check Analysis.) string courses. The final stone placed, thereby As applied to the chemical determination of the closing the arch. constituents of steel or other ferrous metals, the terms "ladle analysis" and "ladle test"are syn- King-Post. (King Rod.) The post member in a onymous and are used to designate the analysis "King-post" type truss or in a "King-post" por- of drillings or chips taken from the small ingot tion of any other type of truss. . or ingots cast from a spoon sample taken from each melt during the pouring (teeming)opera- King-Post Truss. A truss adapted to either tion. wooden or metal bridge construction. It is composed of two triangular panels with a common The term "check analysis" is applied to the vertical. A beam or chord extends the full truss analysis of drillings taken from the finishedma-, length. terial after being rolled, forged or otherwise In the through form of this truss the inclined worked. It is primarily intended asa check de- members are struts and the vertical or King- termination of the results secured from the in- post is a hanger. In the deck truss, the two ingots made at the furnace. Specificationsmay clined members become. tie (tension) members provide a tolerance or margin of variation be- and the vertical becomes a post (compression) tween the ingot and the finished material anal- member. yses. The King-post truss is the simplest of trusses Lagging. See FORMS. belonging to the triangular system. However, it Laminated Timber. Timber planks glued to- is described with equal accuracy asa trussed girder. gether to form a larger member. Laminated timber is used for frames, arches, beams, and K-Truss. A truss having a web system wherein columns. the diagonal members intersect the vertical Lap Joint. A joint in whicha splice is secured members at or near the mid-height. When thus by fixing two elements or members ina position arranged the assembly in each panel formsa wherein they project upon or overlap each letter "K"; hence the name "K-Truss." other. Knee Brace. A member usually short in length, Latch. (Latch Block.) The deviceor mechanism engaging at its ends two other members which commonly provided at one or both ends ofa are joined to form a right angle or a near-right swing span to hold the span in its correct align- angle. It thus serves to strengthen and render ment when in its closed position, and in readi- more rigid the connecting joint. ness for the application of the end wedges or Knee Wall. A return of the abutment backwall lifts. at its ends to enclose the bridge seaton three of Latch Lever. A hand-operated lever attached by its sides. The returned ends may ormay not a rod, cable or chain to the latching device of a serve to retain a portion of the bridge approach movable span and used to engage and to release material, but do hide the bridge seat, beam the latch. ends, and bearings. Lateral Bracing. (Lateral System.) The bracing Knuckle. An appliance forming a part of the assemblage engaging the chords and inclined anchorage of a suspension bridge main suspen- end posts of truss and the flanges of plate gir-

G-25 der spans in the horizontal or inclined planes of span to which the suspending cables are these members to function in resisting the attached. transverse forces resulting from wind, lateral vibration, and traffic movements tending topro- Lift Span. A superstructure span moved byrev- duce lateral movement and deformation. See olution in a vertical plane or by lifting ina BRACING. vertical direction to free a navigable waterway of the obstruction it presents to navigation. See Lattice. (Latticing, Lacing.) An assemblage of MOVABLE BRIDGE. bars, channels, or angles singly or in combination bolted, riveted or welded in inclined posi- Link and Roller. An adjustable device or assem- tion upon two or more elements of a member to blage consisting of a hinged strut-like link fitted secure them in correct position and assure their with a roller at its bottom end, supported upon combined action. When the bars form a double a shoe plate or pedestal and operated by a system by being inclined in opposite directions thrust strut serving to force it into a vertical the assemblageistermed "doublelattice." position and to withdraw it therefrom. When When so arranged the bars are commonlycon- installed at each outermost end of the girdersor nected at their intermediate length intersec- the trusses of a swing span their major functions. tion is to lift them to an extent that their Lattice Truss. In general, a truss having its camber or droop will be removed and the arms web members inclined but more commonly the rendered free to act as simple spans. When the term is applied to a truss having two or more links are withdrawn to an inclined position web systems composed entirely of diagonal fixed by the operating mechanism the span is members at any interval and crossing each free to be moved to an open position. other without reference to vertical members. Lintel Bridge. A bridge having a single span or Vertical members when used perform th func- a series of spans composed of slabs of stone or tions of web stiffeners. They may be utilized for reinforced concrete spanning the interval or in- connecting vertically placed brace frames to the tervals between its substructure elements. gii ders. Lintel Stone. A stone used to support a wall Leaf. The portion of a bascule bridge which over an opening. forms the span or a portion of the span of the structure. Live Load. A dynamic load such as traffic load that is supplied to a structure suddenly or that Ledge Course. In masonry or concrete construc- is accompanied by vibration, oscillation or other tion, a course forming a projection beyond the physical condition affecting its intensity. plane of a superimposed course or courses. The projecting portion may be wash dressed to Loading Girder. A term applied to the girder or mit an unobstructed flow of rain water down girders of a center bearing type swing span, the wall surface. A ledge course differs from a located above the pivot pier and functioning to belt or string course in having a projection only concentrate the superimposed load upon the upon its topmost bed. This construction is also pivot. known as a "Ledger Course." Location. The longitudinal line assumed for Ledge Rock. See BED ROCK. construction purposes, which may or may not coincide with the center line of bridge ; together Lenticular Truss. (Fish Belly Truss.) A truss with the gradients upon the bridge and its ap- having polygonal top and bottom chords curved proachesestablished upon theconstruction in opposite directions with their ends meeting plans and/or on the bridge site preparatory to at a common joint. The chords nearly coincide construction operations. with parabolic arcs. In through spans the floor system is suspended from the joints of the bot- Lock Device. A mechanism which locks the tom chord and the end posts are vertical. movable span of a bridge in its "closed" position and prevents movement to "open" position Lifting Girder. A girder or girder-like member until released. The device on a swing span may engaging the trusses or girders of a vertical lift also be used to lock the span in its "open" posi-

G-26 tion at times when wind or other conditions Milled. In steel fabrication, a careful grinding render this prevention of movement desirable. of an edge or surface to assure good bearing or Locking Mechanism. A general term applied to fit. the various devices used for holding in their Mortar. An intimate mixture, in a plastic condi- closed or traffic service position a bascule, verti- tion, of cement, or other cementitious material cal lift or swing span of any type. This term with fine aggregate and water, used to bed and applies not only to the locking or latching appli- bind together the quarried stones, bricks, or ance but includes also the levers, shafts, gears other solid materials composing the majorpor- or other parts incidental to their service operation of a masonry construction or to produce a tion. plastic coating upon such constructions. Longitudinal Bracing. (Longitudinal System.) The indurated jointing material filling the in- The bracing assemblage engaging the columns terstices between and holding in place the quar- of trestle and viaduct bents and towers in per- ried stones or other solid materials of masonry pendicular or slightly inclined planes located construction. Correspondingly, this term is ap- lengthwise with the bridge structure and func- plied to the cement coating used to producea tioning to resist the longitudinal forces result- desired surface condition upon Inasonrycon- ing from traffic traction and momentum, wind structions and is described as the "mortar or other forces tending to produce longitudinal finish," "mortar coat," "floated face or sur- movement and deformation. See BRACING. face," "parapet," etc. The component ofconcrete composed of M cement, or other indurating material with sand and water when the concrete is a mobile mass Margin. See TOLERANCE. and correspondingly this same component after Masonry. A general term applying to abut- it has attained a rigid condition through hard- ments, piers, retaining walls, arches and allied ening of its cementing constituents. structures built of stone, brick or concrete and Movable Bridge. A bridge of any type having itnown correspondingly as stone, brick or con- one or more span`s capable of being raised, crete masonry. turned, lifted, or slid from its normal vehicular Masonry Plate. A steel plate or a plate-shaped and/or pedestrian service location to provide member whether cast, rolled or foiged, built for the passage of navigation. The movements into or otherwise attached upon an abutment, of the superstructure may be produced either pier, column, or other substructure part to sup- manually or by engine power.. port the rocker, shoe, or pedestal of a beam, Bascule Bridge. A bridge having a super- girder or truss span and to distribute the load structure designed to swing vertically about a to the masonry beneath. fixed oi a moving horizontal axis. The axis may be the center of a hinge pin or trunnion, or it Mattress. A mat-like protective covering com- may be only a line fixing the center of a circular posed of brush and poles, commonly willow, rotation .combined with translation, (rolling lift compacted by wire or other lashings and ties bridge). and placed upon river and stream beds and banks ; lake, tidal or other shores to prevent ero- Vertical Lift Bridge. A bridge having a su__ sion and scour by water movement action. perstructure designed to be lifted vertically by cables or chains attached to the ends of the Meander. The tortuous channel that character- movable span and operating oversheaves izes the serpentine curvature of a slow flowing placed upon the tops of masts or towers or by stream in a flood plain. other mechanical devices functioning to lift the Member. An individualangle,beam.plate span to "open" position and to lower it into its forging, casting or built piece, with or without "closed" position with itsends seated upon connected parts for joints, intended utlimately bridge seat pede.3tals. to become an integral part of an assembled Pontoon Bridge. A bridge ordinarily com- frame or structure. posed of boats, si:ows or pontoons so connected

G-27 to the deck or floor construction that they are framed bent is termed a "Sub-sill" although it retained in position and serve to support vehic- may serve also as a mud sill. ular and pedestrian traffic. A pontoon bridge may be so constructed that a portion is remov- able and thus serve to facilitate navigation. N Modern floating bridges may have pontoons N-Truss. See PRATT TRUSS. built integrally with the deck. Retractile Draw Bridge.(Traverse Draw Natural Slope. See ANGLE OF REPOSE. Bridge.)14,_ bridge having a superstructure de- Neat Line. (Neat Surface.) The general align- si&ned to move horizontally either longitudi- ment position or the general surface position of nally or diagonally from "closed" to "open" po- a face or other surface exlusive or regardless of sition, the portion acting in cantilever being the projections of individual stones, belts, belt counterweighted by that supported upon rollers. courses, copings or other incidental or ancillary Rolling Lift Bridge. A bridge of the bascule projections in a masonry structure. type devised to roll backward and forward upon Neutral Axis. The axis of a member in bending supporting girders when operated throughout along which the strain is zero. On one side of an "open and closed" cycle. the neutral axis the fibers are in tension, on the Swing Bridge. A bridge having a superstruc- other.side in compression. ture designed to revolve in a horizontal plane Normal Roadway Cross Section. The roadway upon a pivot from its "closed" position to an cross section with its crown in countradis- "open" one wherein its alignment is normal or tinction to the superelevated cross sections used nearly normal to the original alignment. For a upon horizontal curves of different degrees of structure having its substructure skewed the curvature and the transition lengths required design commonly provides for revolution in one for their development. direction only and through an arc less than 90°. Nose. A projection acting as a cut water on the The superstructure is balanced upon a center upstream end of a pier. See STARLING. and its ends acting as cantilevers when the end bearings are released may be either equal in Notch Effect. Stress concentration caused by an length or unequal with the shorter one counter- abrupt discontinuity or change in section. Such weighted to permit free revolution movement. concentrations may have a marked effect on fa- A swing bridge with its end bearings released tigue strength of a member. may be supported: (1) upon a single center bearing; (2) upon a circular rim or drum sup- 0 ported upon rollers and (3) upon a center bearing and rim in combination. Operator's House.(Operator's Cabin.)The building containing the power plant and operat- Movable Span. A general term applied to a ing machinery and devices required for the op- superstructure span designed to be withdrawn, erator's (bridge tender's) work in executing the swung, lifted or otherwise moved longitudi- complete cycle of opening and closing a movable nally, horizontally or vertically to free a naviga- bridge span. ble waterway of the obstruction it presents to navigation. Overpass.(Underpass.) The applications of these terms are definitely indicated by their Mud Sill. A single piece of timber or a unit constructions. For any given combination of composed of two or more timbers placed upon a highways, railways, and canals, the basic ele- soil foundation as a support for a single column, ment is a separation of grades. The use of these a framed trestle bent, or other similar member terms is fixed by the relative elevations of the of a structure. traffic ways involved; for the lower roadway, A load distribution piece aligned with and the structure is an underpass ; for the upper placed directly beneath thesillpiece of a roadway, an overpass.

G-28 P When Applied to Welding. The depth to Packing Ring. See SEPARATOR. which the surface metal of the structure part (Structure metal) is fused and coalesced with Paddleboard. Striped, paddle-shaped signsor the fused weld metal to produce a weld joint. boards placed on the roadside in front ofa nar- See WELD PENETRATION. row bridge as a warning. When Applied to Pile Driving. The depth a Panel. (Sub-Panel.) The portion ofa truss span pile tip is driven into the ground. between adjacent points of intersection of web and chord members and, by common practice, Pier. A structure composed of stone, concrete, applied to intersections upon the bottom chord. brick, steel or wood and built in shaft or block- A truss panel divided into two equal or unequal like form to support the ends of the spans of a pa rts by an intermediate web member, gener- multi-span superstructure at an intermediate ally by a subdiagonal or a hanger, forms the location between its abutments. panel division commonly termed "subpanels." The following types of piers are adapted to bridge construction. The first three are func- Panel Point. The point of intersection of pri- tional distinctions, while the remaining types mary web and chord members of a truss. ' are based upon form or shape characteristics. Parabolic Truss. (Parabolic Arched Truss.) A Anchor Pier. A pier functioning to resist an polygonal truss having its top chord and end uplifting force, as for example : The end reac- post vertices coincident with the arc of a para- tion of the anchor arm of a cantilever bridge. bola; its bottom chord straight and its web sys- This pier functions as a normal pier structure tem either triangular or quadrangular. when subjected to certain conditions of super- Parapet. A wall-like member composed of brick, structure loading. stone or reinforced concrete construction upon Pivot Pier. Center Pier. A term applied to the the retaining wall portion of an approach cut, center bearing pier supporting a swing span embankment or causeway or along the outer- while operating throughout an opening-closing most edge of the roadway or the sidewalk por- cycle. This pier is commonly circular in shape tion of a bridge to serve as a protection to ve- but may be hexagonal, octagonal or even square hicular and/or pedestrian traffic. While the in plan. terms balustrade and parapet are used, in a measure, synonymously, the latter is commonly Rest Pier. A pier supporting the end of a regarded as applying to barriers of the block movable bridge span when in its closed position. type without openings within the body portion. Cylinder Pier. A type of pier produced by See BALUSTRADE. sinking a cylindrical steel shell to a desired Parker Truss. See PRATT TRUSS. depth and filling it with concrete. The foundation excavation may be made by open dredging Pedestal. A cast or built-up metal member or as- within the shell and the sinking of the shell may semblage functioning primarily to transmit load proceed simultaneously with the dredging. from one member or part of a structure to another member or part. A secondary function Dumbbell Pier. A pier consisting essentially may be to provide means for longitudinal, of two cylindrical or rectangular shaped piers transverse or revolution movements. joined by a web constructed integrally with A block-like construction of stone, concrete or them. brick masonry placed upon the bridge seat of an Hammerhead Pier. (Tee Pier.) A pier with a abutment or pier to provide a support for the cylindrical or rectangular shaft, and a rela- ends of the beams. tively long, transverse cap. Pedestrian Bridge. See FOOT BRIDGE. Pedestal Pier. A structure composed of stone, Penetration. When Applied to Creosoted Lum- concrete or brick built in block-like form sup- ber. The depth to which the surface wood is porting a column of a bent or tower of a via- permeated by the creosote oil. duct. Foundation conditions or other practical

G-29 considerations may require that twoor more constructed with or without lap or tongued and column supports be placed upon a single base or grooved effect. (3) Rolled steel shapes with full footing section. To prevent accumulation of provision for rigid interlocking of the edges. stream debris at periods of high water or under other conditions the upstream piers may becon- Pile Cap. Concrete footings fora pier or abut- structed with cut-waters and in addition the ment supported on piles. Also applied to the piers may be connected by an integrally built concrete below the pile tops when footing rein- web between them. When composed only of a forcing steel is placed completely above the wide blocklike form, it is called a wall or solid piles. pier. Pile Cut-Off. The portion of a pile removed or to Pile Pier or Bent. A pier composed of driven be removed from its driven butt end to secure piles capped or decked with a timber grillage or the elevation specified or indicated. with a reinforced concrete slab forming the Pile Shoe. A metal piece fixed upon the point or bridge seat. penetration end of a pile to protect it from in- Rigid Frame Pier. Pier with two or more col- jury in driving and to facilitate penetration in umns and a horizontal beam on top constructed every dense earth material. to act like a frame. Pile Splice. One of the means of joining one pile Pier Cap. (Pier Top.) The topmost portion of a upon the end of another to provide greater pen- pier. On rigid frame piers, the term applies to etration length. the beam across the column tops. On hammer- Piling. (Sheet Piling.) General terms applied to head and tee piers, the cap is a continuous beam. assemblages of piles in a construction. See Pilaster. A column-like projection upon a face PILE. surface rarely intended to serve as a structural Pin. A cylindrical bar used as a means of con- member but instead functioning as an architec- necting, holding in position, and transmitting tural treatment to relieve the blankness ofa plane surface. the stresses of, the members forming a truss or a framed joint. To restrain the pin against lon- Pile. A rod or shaft-like linear member of gitudinal movement its ends are fitted with pin timber, steel, concrete, or composite materials nuts, cotter bolts, or both. The nuts are com- driven into the earth to carry structure loads monly of the recessed type taking bearing at thru weak strata of soil to those strata capable their edges upon the assemblage of members. of supporting such loads. Piles are also used To prevent the loosening of the nuts and the where loss of earth support due to scour is ex- displacement of the pins by vibration, joint pected. movements, and other service conditions, the pin ends may be burred or they may be fitted Bearing Pile. One which receives its support with cotters. in bearing through the tip (or lower end) of the pile. Pin-Connected Truss. A general term applied to Friction Pile: One which receives its support a truss of any type having its chord and web through friction resistance along the lateral members connected at the truss joints by pins. surface of the pile. Pinion. The small driving gear on the power- Sheet Piles. Commonly used in the construc- train of a movable bridge. tion of bulkheads, cofferdams, and cribs to re- Pinion Bracket. The frame supporting the turn- tain earth and prevent the inflow of water, liq- ing pinion with its shaft and bearings upon the uid mud, and fine grained sand with water, are drum girder or the loading girder of a swing of three general types, viz.: (1) Timber com- span. posed of a single piece or of two or more pieces spiked or bolted together to produce a com- Pin Joint. A joint in a truss or other frame in pound piece either with a lap or a tongued and which the members are assembled upon a grooved effect. (2) Reinforced concrete slabs cylindrical pin.

G-30 Pony Truss. A general term applied to a truss Pin Packing. An arrangement of truss members having insufficient height to permit the use of on a pin at a pinned joint. an effective top chord system of lateral bracing Pin Plate. A plate or shape riveted or otherwise above the bridge floor. rigidly attached upon the end of a member to Pop-Out. Conical fragment broken out of con- secure a desired bearing upon a pin or pin-like crete surface. Normally about one inch in diam- bearing ; to develop and distribute the stress of eter.Shattered aggregateparticlesusually the joint and/or secure additional strength and found at bottom of hole. rigidity in the member. Portable Bridge. A bridge so designed and con- Pintle. A small steel pin or stud, engaging the structed that it may be readily erected for a rocker in an exansion bearing, thereby permit- temporarycommunication-transportservice ; ting rotation, transferring shear, and prevent- disassembled and its members again reassem- ing translation. bled and the entire structure rendered ready for Pitch. The longitudinal spacing between rivets, further service. studs, bolts, holes; etc., which are arranged in a Portal. The clear unobstructed space of a straight line. through bridge forming the entrance to the Plate Girder. An I-shaped beam composed of a structure. solid plate web with either flange plates or The entire portal member of the top chord flange angles bolted, riveted or welded upon its bracing which fixes the uppermost limit of the edges. Additional cover plates may be attached vertical clearance. See BRACING. The portal of to the flanges to provide greater flange area. a skew bridge is described as a "skew portal." Plinth. See FOOTING. Post. A term commonly applied to a relatively Plinth Course. The course or courses of stone short member resisting compressive stresses, lo- forming the base portion of an abutment, pier, cated vertical or nearly vertical to the bottom parapet or retaining wall and having a projec- chord of a truss and common to two truss pan- tion or extension beyond the general surface of els. Sometimes used synonymously for column. the main body of the structure. See also BASE See COLUMN. and FOOTING. Posted. A limiting dimension, speed, or loading, Plug Weld. (Slot Weld.) A weld joining two e.g., posted load, posted clearance, posted speed, elements of a member or two members so as- indicating larger dimensions and higher speeds sembled that an area of contact will be secured and loads can not be safely taken by the bridge. and the weld produced by depositing weld metal within circular, square, slotted or other shaped Pot Holes. Small worn or distintegrated areas holes cut through one or more of the elements or of bridge floor or approach surface concaved by members. This weld serves to unite the elements the wearing action of vehicle wheels. of a member or to join the members intersecting at truss at other joints of a structure. Pratt Truss. (N-Truss.) A truss with parallel chords and a web system composed of vertical Pointed Arch. See GOTHIC ARCH. posts with diagonal ties inclined outward and Pointing. The operations incident to the com- upward ,from the bottom chord panel points to- pacting of the mortar in the outermost portion ward the ends of the truss except the counters of a joint and the troweling or other treatment required in midlength panels. The Parker Truss of its exposed surface to secure water tight- is an adaptation of the Pratt Truss by making ness or desired architectural effect or both. the top chord polygonal in shape. Polygonal Truss. A general term applied to a Priming Coat. (Base Coat.) The first coat of truss of any type having an irregular or "bro- paint applied to the metal or other material of a ken" alignment of straight top chord members bridge. For metal structures this is quite com- which forms with the end posts and the bottom monly a fabricating shop application and is, chord the perimeter of a polygon. therefore, termed the "shop coat."

G-31 Protection Fence. See GUARD RAILING. approach to a bridge and commonly applied to a rather steep incline. Protection Railing. See GUARD RAILING. Random Stone. A general term applied to quarried stone block of any dimensions whether in- Q tended for ashlar or for random masonry con- Queen-Post Truss. A parallel chord type of struction. truss adapted to either timber metal bridge Range of Stress. The algebraic difference be- construction, having three panels with one of tween the minimum and maximum stresses in a the chords occupying only the length of the member or in an element or part thereof either center panel. Unless center panel diagonals are computed to be produced by a given condition of provided, it is a trussed beam. loading or produced by its actual service loading. R Rebar. A steel reinforcing bar. Redundant Member. A member in a truss or Rack. A bar with teeth on one of its sides, de- frame which renders it a statistically indetermi- signed to mesh with the gears of a pinion or nate structure. The structure would be stable worm. The rack is usually attached to the mov- without the redundant member whose primary ing portion of a movable bridge and receives the purpose is to reduce the stresses carried by the motive power from the pinion. determinate structure. Radial Rod. (Spider Rod.) A radially located tie Re-Entrant Corner. A corner with more than rod connecting the roller circle of a rim-bearing 180° of material and less than 180° of open swing span with the center pivot or center bear- space. ing casting. Reinforcing Bar. A steel bar, plain or with a Radial Strut. A radially located brace member deformed surface, which bonds to the concrete of the drum construction of a rim-bearing and supplies tensile strength to the concrete. swing span. Retaining Wall. A structure designed to re- Railing. (Handrail.) A wooden, brick, stone, strain and hold back a mass of earth. concrete or metal fence-like construction built at the side of the roadway, or the sidewalk, Buttressed Wall. A retaining wall designed upon the retaining wall portion of an approach with projecting buttresses to provide strength cut, embankment, or causeway or at the outer- and stability. most edge of the roadway or the sidewalk por- Counterforted Wall. A retaining wall designed tion of a bridge to guard or guide the movement with projecting counterforts to provide strength of both pedestrian and vehicular traffic and to prevent the accidental passage of traffic over and stability. the side of the structure. Gravity Wall. A wall composed of brick, The term "handrail" is commonly applied stone or concrete masonry designed to be stable only to railing presenting a latticed, barred, againstsliding and rotation(overturning) balustered or other open web construction. upon its foundation or upon any horizontal plane within its body by virtue of its shape and Rake. The slope, batter or inclination from a horizontal, vertical or other assumed plane, of weight. the sides of an embankment or other inclined Reinforced Concrete Cantilever Wall. A wall earth construction ; the batter of a face or other consisting of a base section integral with stem surface of masonry ; of the plane of a truss side constructed approximately at a right angle of a tower or other portion of a bridge super- thereto giving its cross section a letter "L" or structure or of any member thereof. an inverted "T" shape. The stem portionresists Ramp. An inclined traffic-way leading from one the horizontal or other forces tending to pro- elevation to another. The general term used to duce overturning by acting as a cantilever designate an inclined roadway and/or sidewalk beam.

G-32 Rigid Frame Bridge. A bridge with rigid or mo- general use of vehicular or vehicular and pedes- ment resistant connections between deck slabs trian traffic. In general, its width corresponds or beams and the substructure walls or col- (1) to the distance curb to curb ;(2) to the dis- umns, producing an integral, elastic structure. tance between the outside limits of sidewalks ; The structure may be steel or concrete. or (3) to the width of the roadway pavement or In general this type of bridge may be re- traveled way when no curbs exist. garded as a form of arch or curved beam hav- Roadway Shoulder Area. (Shoulder Area.) The ing its intermediate intradosal section or por- portion or area of the top surface of an ap- tion either straight or slightly curved and its proach embankment, causeway, or cut immedi- end sections located normal to the straight por- ately adjoining the roadway, used to accommo- tion or to the tangent of the curved one at its date stopped vehicles in emergencies and to lat- center length position. erally support base and surface courses. Rim Girder. See DRUM GIRDER. Rocker Bearing. A cylindrical, sector-shaped Rim. Plate. Toothed or plain segmental rim on a member attached by a pin or trunnion at its rolling lift bridge. axis location to the expansion end of a girder or truss and having line bearing contact upor its Ringbolt. See EYEBOLT. perimetral surface with the masonry pla,,d or Ring Stone. See VOUSSOIR. pedestal, thus providing for the longitudinal movements resulting from temperature chant Riprap. Brickbats, stones, blocks of concrete or and superimposed loads by a wheel-like transh. other protective covering material of like nation. ture deposited upon river and stream beds and The design condition that the entire reaction banks, lake, tidal or other shores to prevent ero- stress is concentrated upon a line contact ren- sion and scour by water flow, wave or other ders it especially essential that the masonry movement. plate or pedestal be accurately leveled and that Rise of an Arch. For a symmetrical arch ; the the rocker be carefully adjusted to secure a uni- vertical distance from the chord through its form even bearing thereon. A relatively large springing lines to the intrados at its crown. percentage of this type of bearings lack correct For an unsymmetrical arch, assumed to be in adjustment. a normal vertical position, the vertical distances Rocker Bent. A bent composed of metal, rein- from its springing lines to the intrados at its forced concrete or timber, hinged or otherwise crown. articulated at one or both ends to provide the Riveted Joint. (Bolted Joint.) A joint in which longitudinal movements resulting from temper- the assembled elements and members are united ature changes and the superimposed loads of by rivets. The design of a riveted joint contem- the span or spans supported thereon. plates a proper distribution of its rivets to de- Rocker and Camshaft. An adjustable bearing velop its various parts with relation to the device or assemblage consisting of a rocker stresses and the purposes which each must bearing combined with a camshaft, properly serve. mounted and geared to produce by its rotation a A bolted joint differs from a riveted one only vertical lifting action, reacting upon a shoe in the use of bolts as the uniting medium in- plate or pedestal fixed upon the bridge seat. stead of rivets. The conditions of design are When installed at each outermost end of the generally the same, but different allowable unit girders, or the trusses of a swing span, the lift- stresses are employed. ing action raises them to an extent that their camber or droop will be removed and the areas Roadway. (Travel Way.) 1. The portion of the rendered free to act as simple spans. When the deck surface of a bridge intended for the use of camshafts are revolved through an angle of vehicular or vehicular and pedestrian traffic. 2. 180° from their total or full lift position the The top surface portion of an approach em- rocker bearings are released and lifted and the bankment, causeway or cut intended for the span is free to be moved to "open" position.

G-33 Rolled Beams, Rolled Shapes. See STRUC- Run-off is dependent upon soil porosity (varied TURAL SHAPES, WIDE FLANGE BEAMS. by saturated or frozen condition), slope or soil surfaces, intensity of rainfall or of melting Roller. 1. A steel cylinder forming an element snow conditions, and other pertinent factors. of a roller nest or any other device or part intended to provide movements by rolling contact. S The so-termed "segmental roller" consisting es- Saddle. A member located upon the topmost sentially of two circular segments integrally portion of the tower of a suspension bridge, de- joined by a web-like portion is used in the con- signed to support the suspension cable or chain struction of roller nests requiring relatively and to provide for its horizontal movements re- large bearing length with the least practicable sulting from elastic deformations induced by shoe plate area and a correspondingly decreased temperature changes and the stresses incident weight of metal in the entire assemblage. 2. One to the service loadings. of the wheel-like elements forming the roller circle of a rim-bearing swing span. Safe Load. The maximum loading determined by a consideration of its magnitudes and distri- Roller Bearing. A single roller or a group of butions of wheel, axle or other concentrations rollers so housed as to permit movement of a as productive of unit stresses in the var.,:g,is part or parts of a structure thereon. members and incidental details of a structure, Roller Nest. A group of steel -ylinders forming permissible for service use, due consideration a part of the movr!,7 , end of a girder or truss being given to the physical condition of the and located between the masonry plate and shoe structure resulting from its previous service or pedestal to facilitate the longitudinal move- use. ments resulting from temperature changes and Safety Curb. A narrow curb between 9 inches superimposed loads. Commonly the rollers are and 24 inches wide serving as a refuge or walk- assembled in a frame or a box. Roller nests may way for pedestrians crossing a bridge. be used for other services than those herein described. The term "Expansion Rollers" is some- Sag. A deformation of an entire span; of any times used synonymously for roller nest. part of a span, or of one or more of its members from the horizontal, vertical, or inclined posi- Roller Track. The circular track upon which the tion intended as a condition of its original de- drum rollersof a rim-bearing swing span sign and construction. This variation may re- travel. This is sometimes described as the lower sult from elastic deformation of structural ma- track. terial; from irregularities produced by inade- Roller Tread. See TREAD PLATES. quate temporary supports during the progress of construction operations; or from incorrect Rolling Lift Bridge. See MOVABLE BRIDGE. adjustments and unworkmanlike procedures Rubble. Irregularly shaped pieces of stone in made a part of the work. the undressed .condition obtained from the In existing structures sag may be attributa- quarry and commonly ranging in size from rela- ble to (1) original construction irregularities ; tively small usable pieces to one-man or two- (2) to excessive stresses resulting from over- man stones. This term is also applied to large loading; (3) to corrosion, decay or other deteri- boulders and fragments requiring mechanical oration of the structure materials, and (4) equipment for handling. When shaped ready for plastic flow of material. use in rubble masonry; this stone is commonly The total deflection of the cable members of a described as "worked" or "dressed" rubble. suspension bridge. The so-termed "sag ratio" is Run-Off. As applied to bridge design, the por- the relation existing between the sag and the tionof theprecipitation upon a drainage length of span. (catchment) area which is discharged quickly Sag Rod. A rod usually fitted with threads and by its drainage stream or streams and which, nuts at its ends ;used to restrain a structure therefore, becomes a factor in the design of the member from sagging due to its own weight or effective water discharge area of a bridge. to external force or forces.

G-34 Sash Brace. (Sash Stay, Sash Strut.) A hori- provide open spaces beneath the latter for zontal or nearly horizontal piece bolted or oth- draining rain or other water accumulation from erwise secured upon the side of a pile or framed the floor surface. bent between the cap and ground surface or the Seam Weld. A weld joining the edges of two cap and sill, as the case may be, thus adding elements of a member or of two members placed rigidity to the assemblage. in contact. This .veld serves to form a continu- The horizontal member in a tier of bracing ous surface wIlether plane or curved, and to attached to a timber, reinforced concrete, or prevent infiltration of moisture between the metal trestle bent or tower. parts. In general, it is not a stress carrying Scab. (Scab Piece.) A plank spiked or bolted weld. over the joint between two members to hold Seat Angle. (Shelf Angle.) A piece of angle at- them in correct adjustment and strengthen the tached upon the side of a column girder or other joint. member to provide support for a connecting A short piece of I-beam or other structural member either temporarily during its erection shape bolted, riveted or welded upon the flange or permanently. The outstanding leg of the and/or web of a metal pile to increase its re- angle may be strengthened by a stiffener placed sistance to penetration. Similarly, for the same vertically beneath it. purpose, a piece of dense hardwood fitted upon Segmental Girder and Track Girder. These the flange ar_d/or web and having bearing upon terms apply to the rolling lift type of bascule a lug angle at one or both its ends. bridge combining circular rotation and transla- Scour. An erosion of a river, stream, tidal inlet, tion movements in the "opening-closing" cycle. lake or other water bed area by a current, wash The term "segmental girder" is used to desig- or other water in motion, producing a deepen- nate one of the movable operating girders of a ing of the overlying water, or a widening of the span or leaf to which a span girder or truss is lateral dimension of the flow area. rigidly attached. It commonly consists of a plate girder having its bottom flange curved to form Screw Jack and Pedestal. An adjustable device a segment of a circle. This curved flange is or assemblage consisting of a screw operated fitted with tread castings which take line bear- within a fixed nut and having upon its bottom ing contact upon the tread castings fitted upon end a pedestal-like bearing conjoined with it by the top flange of the supporting track girder a ball and socket or other equally adaptable ar- with which they interlock to insure positive ticulation permitting its adjustment upon a translation movement. shoe plate or pedestal fia ed upon the bridge seat. When installed at each outermost end of the The term "track girder" is used to designate girders or the trusses of a swing span their one of the plate girders or trusses intended to major function is to lift them to an extent that provide support for the movable span through- their camber or droop will be removed and the out an "opening-closing" cycle. Its tread cast- arms rendered free to act as simple spans. ings fitted upon its top flange or chord form the track upon which the segmental girder moves Scupper. (Curb Inlet.) An opening in the floor by a rack and pinion-like action. portion of a bridge, commonly located adjacent Segmental Rim. The curved rim or circular seg- to the curb or wheel guard, to provide means ment of a rolling lift bridge. for rain or other water accumulated upon the roadway surface to drain through it into the Seizing. The ligature of wire or other material space beneath the structure. Bridges having applied upon a suspension bridge cable to hold reinforced concrete: floors with concrete curbs the individual wires in satisfactory contact con- may be effectively drained through scuppers lo-- dition. cated within the curb face surfaces. Separator. See SPREADER. Scupper Block. One of the short wooden pieces Shafts. Pieces conveying torsion stress only, fixed between the wooden planks of a bridge which are, in general, used only in movable floor and the bottom side of the wheel guard to structures.

G-35 Shear Lock. (Heel Stay, Tail-Lock.) The device which may take bearing directly upona ma- or mechanism provided at the heel of a bascule sonry plate or upon an intervening expansion span to engage and hold the leaf in its closed device. position and prevent rotation. Snore. A strut or prop placed ina horizontal, Sheave. A wheel having a groove or grooves in inclined or vertical position againstor beneath its face surface. This term may be applied a structure or a portion thereof to restrain collectively to include both the sheave and its movement. housing block. Shoulder Area. See ROADWAY SHOULDER Sheave Girder. A girder or girder-like member AREA. supporting the operating cable sheaves at the Sidewalk. The portion of the bridge floorarea top of a tower of a vertical lift bridge. serving pedestrian traffic only and, for safety Sheave Hood. A protecting covering placed and convenience to its users, commonly elevated above a sheave engaging the suspending cables above the portion occupied by vehicles. of a vertical lift bridge to prevent accumula- Sidewalk Bracket. As applied to metal structions of moisture, sleet and ice upon the sheave tures: A trianguar shaped frame attached to face. and projecting from the outside of a girder, Sheet Pile Cofferdam. In general a wall-like, truss or bent to serve as a support for the side- watertight or nearly watertight barrier com- walk stringers, floor and railing or parapet. In posed of driven timber or metal sheet pi'l,.g general, these brackets are in effect a cantilev- constructed to surround the area to be occupnd ered extension of the floor beams and are com- 13y an abutment, pier, retaining wall or other monly connected to them by bars or other ten- structure and permit unwatering of the enclo- sion pieces designed to sustain the bending mo- sure so that the excavation for the preparation ment at the junction plane. of a foundation and the abutment, pier or other As applied to reinforced concrete structures : construction may be produced in the open air. A cantilever beam commonly triangular in The alignment of the piles may be facilitated by shape, attached to and projecting from the out- the use of walers, struts and ties. side of a girder, truss, or bent to serve as a This type of darn is adapted to construction support for the sidewalk floor slab and the rail- located in still or slow flowing', shallow water. ing or parapet. Its watertightness is sometimes rendered more Sill. (Sill Piece.) The base piece or member of a complete by depositing earth material against viaduct or trestle bent serving to distribute the the exterior side of the dam. column loads directly upon the foundation or Sheet Piling. (Sheeting.) A general or collective upon mud sills embedded in the foundation soil term used to describe a number of sheet piles transversely to the alignment of the bent. taken together to form a crib, cofferdam, bulk- Silt. Very finely divided siliceous or other hard head, etc. and durable rock material derived from its Shelf Angie. See SEAT ANGLE. mother rock through attritive,or other mechanical action rather than chemical decomposition. Shim. A comparatively thin piece of wood, In general, its grain size shall be that which stone, or metal inserted between two elements, will pass a Standard No. 200 sieve. pieces or members to fix their relative position and/or to transmit bearing stress. Simple Span. A superstructure span having,at each end, a single unrestraining bearing or sup- Shoe. In general, a pedestal- shaped member at port and designed to be unaffected by stress the end of a plate girder or truss functioning to transmission to or from an adjacent span or transmit and distribute its loads to a masonry structure. bearing area or to any other supporting areaor member. A shoe may be a cast or a built-up S-I-P Forms. See FORMS. member ; the base plate or plate-like part of Skew. Angle. As applied to oblique bridges; the which is commonly termed the "shoe plate," skew angle, angle of skew or simply "skew" is

G-36 the acute angle subtended by a line normal to Slope, Pavement. (Slope Protection.) A thin the longitudinal axis of the structure and a line surfacing of stone, concrete or other material parallel to or coinciding with the alignment of deposited upon the sloped surface of an approach its end. cut, embankment or causeway to prevent its Skewback. The course of stones, in an abutment disintegration by rain, wind or other erosive or pier, located at the extremity of an arch and action. having its beds inclined (battered) as required Slot Weld. See PLUG WELD. to transmit the stresses of the are.. The bed Soffit. See INTRADOS. adjoining the voussoirs forming the first string course of the arch ring will be normal to the Sole Plate. A plate bolted, riveted, or welded axis of the arch. The individual stones of the upon the bottom flange of a rolled beam, plate skewback course are designated "skewback girder, or truss to take direct bearing upon a stones." roller nest, bearing pedestal, or masonry plate. A casting or a combination of castings; or a It distributes the reaction of the bearing to the built-up member designed to function as a beam, girder, or truss member. The sole plate skewback. may also function as a combined sole and masonry plate at the fixed end of a beam, girder, Skewback Shoe. ( Skewback Pedestal.) The shoe or truss. or pedestal member, transmitting the thrust of a trussed arch or a plate girder arch to the Soldier Beam. A steel pile driven into the earth with its butt end projecting, used as a canti- skewback course or cushion course of an abut- lever beam to support horizontal lagging retain- ment or pier. Skewback shoes and pedestals are ing an excavated surface. commonly hinged. Spalls. Circular or oval depression in concrete Slab. A thick plate, usually of reinforcedcon- crete, which supports load by flexure. It is caused by a separation of a portion of thesur- usually treated as a widened beam.. face concrete, revealing a fracture parallel with or slightly inclined to the surface. Usually part Slab Bridge. A bridge having a superstructure of the rim is perpendicular to the surface. composed of a reinforced concrete slab con- The pieces of spelled concrete themselves. structed either as a single unit or as a series of narrow slabs placed parallel with the roadway Span. This term has various applications de- alignment and spanning the space between the pending upon its use whether in design, in field supporting abutments or other substructure construction, or in its common nontechnical application, viz.: parts. The former is commonly constructed in place but the latter may be precast. When applied to design of a beam, girder, truss or arch structure. The distance center to Slag Inclusion. Small particles of slag trapped center of the end bearings or the distance be- inside a weld during the fusion process. tween the lines of action of the reactions whether induced by substructure or othersup- Sleeve Nut. A device used to connect the ele- porting members. ments of an adjustable rod or bar member. It consists of a forging having an elongated nut- When applied to the field construction of sub- shaped body with right- -and left-hand threads structure abutments and piers. The unobstructed space or distance between the faces of within its end portions, thus permitting its ad- the substructure elements. For arch structures justment with a wrench to providea desired this length is measured at the elevation of the tension in the member. springing lines. These lengths or dimensions Slenderness Ratio. Measure of stiffness ofa are commonly referredtoas"clear span member, expressed as the length of the member length." See CLEAR SPAN. divided by its radius of gyration. The complete superstructure of a singlespan bridge or a corresponding integral partor unit Slope. A term commonly applied to the inclined of a multiple span structure. This application of surface of an excavated cut or an embankment. "span" is rendered more specific when subdi-

G-37 vided into: (a) Fixed Span : A superstructure structure or group of structures. The special anchored in its location upon the substructure items may either designate and authorize de- and (b) Movable Span : A superstructure in- partures from the "standard" or apply entirely tended to be swung or lifted to provide an unob- to requirements and conditions not dealt with structed waterway space for the passage of therein. The status of these supplemental or waterborne traffic. special specifications is commonly fixed by the Spandrel. The space bounded by the arch extra- "standard" specifications. Likewise the "standard" specification commonly recognizes the pos- dos, the st000tructure abutments and/or pier (s), and the roadway surface or other elevation sibility of discrepancies between the specifica- limit -fixed by the construction details. tions and the general plans and working (detail) drawings by fixing a coordination status Spandrel Column. A column superimposed upon for such occurrences. the ring or a rib of an arch span and serving as a support for the deck construction of an open Spider. The collar-like plate connecting the spi- spandrel arch. See-OPEN SPANDREL ARCH. der frame of a rim bearing or a combined rim and center bearing swing span. to the pivot. Spandrel Fill. The filling material placed within the spandrel space of a spandrel arch. Spider Frame. The frame assemblage of struts, radial rods, spacer rings and roller adjusting Spandrel Tie. A wall or a beam-like member devices holding the conical roller ring of a rim connecting the spandrel walls of an arch and bearing or a combined rim and center bearing securing them against bulging and other defor- swing span in correct position with relation to mation. In stone masonry arches the spandrel the pivot. tie walls served to some extent as counterforts. In reinforced concrete spandrel archspans Spider Rod. See RADIAL ROD. spandrel tie walls may likewise serve as coun- Splay Saddle. A member at the anchorage ends terforts. See TIE WALLS. of suspension bridge cables which permits the Spandrel Wall. A wall built upon an arch to wires or strands to spread so that they may be function as a retaining wall for the spandrel fill connected to the anchorage. and the roadway in a spandrel filled structure; Splice. This term has two applications depend- but, when the spandrel is not filled, to support ing upon its use whether in design or in shop the floor system and its loads. In wide struc- and field construction, viz.: tures having unfilled spandrels one or more in- When applied to design and the development terior walls may be used, thus providing a cellu- of construction details : The joining or uniting lar construction when combined with tie walls. of elements of a member, par is of -a member or See TIE WALLS. members of a structure to provide desired con- Specifications. A detailed enumeration of the ditions for the transmittal of stress and the de- chemical and physical properties determining velopment of rigidity and general strength ful- the quality of construction materials together filling the service requirements of the member with requirements for handling, shipping and or of the structure of which it is a part. storage thereof; the conditions governing the When applied to shop and field construction: loads, load applications and unit stresscon- the complete assemblage of parts used in pro- siderations of bridge foundation, substructure ducing the union of elements of a member or and superstructure design ; the development of members of a structure. construction details and their applications in- Splice Joint. A joint in which the elements of a cident to fabrication ; erecton or other construc- ton procedures pertinent to the production of member or the members of a structure are serviceable bridge structures. joined by a splice plate or by a part or piece functioning to secure a required amount of When general or so called "standard" specifi- strength and stability. cations are used, it occasionally becomesneces- sary to supplement the requirements by items Spreader. 1. A cast or fabricated piece used to having specific application to a given bridge hold angles, beams, channels or fabricated

G-38 ge' pieces or parts in the locations or positions in or chain by restraining the deformations of the which they function as parts of a member or latter and by distributing the concentrated or structure.2. A ring-like or sleeve-like piece other irregularly distributed loads thus resist- placed upon a pin to hold the eyebars or other ing and controlling the vertical oscillations of members assembled upon itin their correct the floor system imparted to it by the cable or member positions. This piece is sometimes de- chain deformations. scribed as a "pin-filler," or "packing ring." Stirrup. In timber and metal bridges: A U- Springing Line. The line within the face sur- shaped rod, bar or angle piece providing a stir- face of an abutment or pier at which the intra- rup-like support for an element of a member or dos of an arch takes its beginning or origin. a member. Starling. An extension at the upstream end In reinforced concrete bridges: A U-shaped only, or at both the upstream and downstream bar placed in beams, slabs or similar construc- ends of a pier built with surfaces battered thus tions to resist diagonal tension stresses. forming a cutwater to divide and deflect the Stirrup Bolt. A U-shaped rod or bar fitted at its stream waters and floating debris and, corre- ends with threads, nuts and washers and used spondingly, when on the downstream end, func- to support streamer or other timber pieces of tioning to reduce crosscurrents, swirl and eddy wooden truss structures suspended from the action which are productive of depositions of bottom chord. sand, silt and detritus downstream from the pier. Stone Facing. (Stone T'neer, Brick Veneer.) A stone or brick surface cc vering or sheath laid in Statics. The branch of physical science which is imitation of stone or brick masonry but having concerned with bodies acted on by balanced a depth thickness equal to the width dimension forces. Therefore, these bodies are either at rest of one stone or brick for stretchers and the or static. length dimension for headers. The backing por- Stay-In-Place Forms. See FORMS. tion of a wall or the interior portion of a pier may be constructed of rough stones imbedded in Stay Plate. (Tie Plate.) A plate placed at or mortar or concrete, cyclopean concrete, plain or near the end of a latticed side or web of a com- reinforced concrete, brick bats imbedded in pression or other member and also at intermedi- mortar, or even of mortar alone. The backing ate locations where connections for members in- and interior material may be deposited as the terrupt the continuity of the latticing. This laying of the facing material progresses to plate serves to distribute the lattice bar stress secure interlocking and bonding with it, or the to the elements of the member and adds stiff- covering material may be laid upon its pre- ness and rigidity to joint assemblages. formed surface. Stem. The vertical wall portion of an abutment Strain. The distortion of a body produced by retaining wall, or solid pier. See also BREAST- the application of one or more external forces WALL. and measured in units of length. In common usage, this is the proportional relation of the Stiffener. An angle, tee, plate or other rolled amount of distortion divided by the original section riveted, bolted or welded upon the web length. of a plate girder or other "built-up" member to transfer stress and to prevent buckling or other Stress. The resistance of a body to distortion deformation. when in a solid or plastic state and when acting in an unconfined condition. Stress is produced A stiffener forged at its ends to fit upon the by the strain (distortion) and holds in equilib- web and the web-legs of the flange angle2 of a rium the external forces causing the distortion. plate girder is termed "crimped." It is measured in pounds or tons. Within the Stiffening Girder, Stiffening Truss. A girder or elastic limit the strain in a member of a struc- truss incorporated in a suspension bridge to ture is proportional to the stress in that mem- function in conjunction with a suspension cable ber.

G-39 Allowable Unit Stress. As applied to the in- drawing. A future investigation of a given vestigation of an existing structure in deter- structure to deterrn;ne its reliability for a given mining its adequacy for existing or prospective load or combination of loads may be greatly service ; it is the stress per unit of area of the facilitated and expedited by an adequate stress material of the ent;:te structure or any portion sheet record of its original design conditions. or member thereof which is determined to be a Stringer. A longitudinal beam supporting the safe unit for service use, due cons: eration bridge deck, and inlarge. bridges or truss being given to the quality of the material, phys- bridges, framed into or upon the door beams. ical condition, the adequacy of the construction details or other physical factors incident or per- Structural Members. Basically these are of tinent to the service conditions to which they three types, viz.: (1) Ties: Pieces subject to are or will be subjected and, if necessary, to the axial tension only ;(2) Columns or Struts : conditions contemplated to exist in the event of Pieces subject to axial compression only ;(3) repair, r: placement or strengthening opera- Beams : Pieces transversely loaded and subject tions. to both sh.r and bending moment. However, the arrangement of the members of Unit Stx;:ss. The stress per square inch (or a structure and the application of its design other unit of surface or crosssectional area). loads may embody combinations of these bask The Allowable Unit Stress is :(a) Assumed in stress types. determining the composition and construction details of a memer or the members of a pro- Structural Shapes. As applied to bridge struc- posed structure, or (b) assumed for judging the tures : The various types and forms of rolled safe load-capacity of an existing structure ; iron and steel having flat, round, angle, channel, while working stress is (c) produced in the "I", "H", "Z" and other cross-sectional shapes members and parts of an existing structure adapted to the construction of the metal mem- when subjected to loads, impacts and other bers incorporated in reinforced foundations, stress-producing elements and factors to which substructures and superstructures. the structure is proposed to be or may have Structural Tee. A tee-shaped rolled member been subjected. formed by cutting a wide flange longitudinally along the centerline of web. Working Stress. The unit stress in a member under service or design load. Strut. A genes al term applying to a piece or member acting to resist compressive stress. Stress Sheet. A drawing showinga structure in skeletal form sufficient only to impart or sug- Sub-Panel. See PANEL. gest in conjunction with notations thereon its Subpunched and Reamed Work. A term applied general makeup, major dimensions and the ar- to structural steel shapes having rivet holes rangement and composition of itsintegral punched a specified dimension less in diameter parts.Special constructiondetails may be than the nominal size of the rivets to be driven shown by section views and sketches with or therein and subsequently reamed to a specified without dimensional data. Upon the skeletal out- diameter greater than the rivet size. line of the structure or in tabulated form the This term is also applied to completely assem- drawing should show the computed stressesre- bled and riveted members and structures in sulting from the application of a system of loads which the rivet holes have been produced by together with the design composition of the in- subpunching and reaming procedure. dividual members resulting from the application of assumed unit stresses for the materialor Substructure. The abutments, piers, grillage or materials to be used in the structures. Theas- other constructions built to support the span or sumed design load or loads should appear either spans of a bridge superstructure whether con- in diagrammatic form with dimensions and sisting of beam, girder, truss, trestle or other magnitudes, or reference be made to readily type or types of construction. available information relating thereto bya spe- Sump. A pit or tank-like depression or recepta- cialnote conspicuously displayedupon the cle into' which water is drained. The removal of

G-40 the water so accumulated may be effected by Suspension Bridge. A bridge in which the floor pumping or by siphoning. system and its incidental parts and appliances are supported in pract;cally a horizontal posi7 Superelevation. (Curve Banking.) The trans- tion by being suspendeu upon cables which are verse inclination of the roadway surface within supported at two or more locations upon towers a horizontal curve and the relatively short tan- and are anchored at their extreme ends. The gent lengths adjacent thereto required for its cables constitute the main suspension members full development. The purpose of superelevation and commonly their anchorage may be one, of is to provide a means of resisting or overcoming three forms, viz.:(1) By extension of these the centrifugal forces of vehicles in transit. members beyond the towers to the anchorages ; Superstructure. The entire portion of a bridge (2) By fixing their ends upon the towers and structure which primarily receives and sup- backstaying the towers against overturning by ports highway, railway, canal, or other traffic the suspension members pulling upon them; (3) loads and in its turn transfers the reactions re- By an integral inclusionof the anchorages sulting therefrom to the bridge substructure. within the structure whereby the entire hori- The superstructure may consist of beam, gir- zontal and vertical components of the main sus- der, truss, trestle or other type or types of con- pension member stresses are resisted by a rigid struction. floor system construction functioning asa A superstructure may consist of a single span column, upon the extreme ends of which the upon two supports or of a combination of two or main suspension members are securely con- more spans having the number and distribution nected. This form is commonly described as of supports required by their types of construc- "self anchored." tion, whether consisting of simple, continuous, Suspension Cable. (Suspension Chain.) One of cantilever, suspension, arch or trestle span-tow- the main members upon which the floor system er-bent construction. of a suspension bridge is supported. Its ends Surcharge. An additional load placed atop exist- may be fixed at the tops of towers which are backstayed to resist the horizontal components ing earth or dead loads. In the case of abut- of the cable or chain stresses or instead it may ments and retaining walls, the surcharge load is rest upon saddles at the tops of two or more assumed to be replaced by an earth load of towers and be extended and fixed upon anchor- equivalent total weight. age members. When the extension portions Suspended Span. A superstructure span having from the tops of towers to the anchorages do one or both of its ends supported upon or from not directly support any part of the bridge adjoining cantilever arms, brackets or towers, floor, they function essentially as backstays ; and designed to be unaffected by other stress but when they engage floor suspenders located transmission to or from an adjacent structure. between the towers and anchorages they func- The ordinary use of a suspended span is in tion as suspension cables for the end spans of connection with cantilever span construction. the structure. Suspender. A wire cable, a metal rod or bar Sway Anchorage. (Sway Cable.) A guy, stay designed to engage a cable band or other device cable or chain attached at an intermediate connecting it to the main suspension member of length location upon the floor system of a sus- a suspension bridge at one end and a member of pension bridge and anchored upon the end por- the bridge floor system at the bther thus per- tion of an abutment or pier or in the adjacent mitting it to assist in supporting the bridge land surface to increase the resistance of the floor system and itssuperimposed loads by suspension span to lateral movement. transferring loads to the main suspension members of the structure. Sway Brace. 1. A piece bolted, or other wise se- A member serving to support another mem- cured in an inclined position upon the side of a ber in a horizontal or an inclined position pile or frame bent between the cap and ground against sagging, twisting or other deformation surf ace or the cap and sills, as the case may be, due to its own weight. to add .rigidity to the assemblage. See BRAC-

G-41 ING. 2. An inclined member in a tier of bracing ducing the amount of flow through the water- forming a part of a timber, metal, or R/C bent way. Tailwater is expressed in terms of its or tower. 3. One of the inclined members of the depth. See also HEADWATER. sway bracing system of a Metal girder or truss Temporary Bridge. A structure built for emer- span. In plate girder construction the term X- gency or interim use to replace a previously ex- brace is sometimes used. isting bridge demolished or rendered unservice- Sway Frame. A complete panel or frame of able by flood, fire, wind or other untoward sway bracing. See BRACING. occurrence, or instead, to supply bridge service required for a relatively short period. Swedge Bolt. See ANCHOR BOLT. Tendon. A prestressing cable or strand. Swing Span. A superstructure span designed to be entirely supported upon a pier at its center, Tension. An axial force or stress caused by when its end supports have been withdrawn or equal and opposite forces pulling at the ends of released, and equipped to be revolved in a hori- the members. zontal plane to free a navigable waterway of the Throat. Of a fillet weld. The dimension normal obstruction it presents to navigation when in its to the sloping face of a fillet weld between the normal traffic service position. See MOVABLE heel of the weld and the sloping faces. BRIDGE. Through Bridge. A bridge having its floor ele- Swing Span Pivot. The center casting upon or vation more nearly at the elevation of the bot- about which the movable portion of a swing tom than at the top portion of the superstruc- span revolves in making an opening-closing ture, thus providing for the passage of traffic cycle. between the supporting parts. In the center bearing type span, this casting Tide Gate. See FLOOD GATE. functions not only as a pivotal member but also as the support for the movable span when the Tie Plate. See STAY PLATE. . ene. lifting device is released. Tie Rod. (Tie Bar.) A rod-like or bar-like mem- In the rim-bearing type span this casting ber in a truss or other frame functioning to functions as a pivotal anchor member regulat- transmit tensile stress. ing the location of the movable parts throughout an opening-closing cycle but does not sup- Tie Walls. (Spandrel Tie Wall.) One of the port the movable span. Walls built at intervals above the arch ring to tie together and reinforce the spandrel walls. See In the combined center and rim-bearing type DIAPHRAGM WALL. this casting functions as a support for a portion of the weight of the movable span when the end Any wall designed to serve as a restraining lifting device is released. member to prevent bulging and distortion of two other walls connected thereby. T Toe of Slope. The location defined by the in- Tack Weld. A weld of the butt, fillet or seam tersection of the sloped surface of an approach type intended only to fix an element of a mem- cut, embankment or causeway or other sloped ber or a member of a structure in correct ad- area with the natural or an artifical ground sur- justment and position preparatory to fully face existing at a lower elevation. welding. Tack welds may be used to restrain Toe Wall. (Fpotwall.) A relatively low retain- welded parts against deformation and distor- ing wall placed near the "toe-of-slope" location tion resulting from expansion of the metal by of an approach embankment or causeway to atmospheric and welding temperatures. produce a fixed termination or to serve as a Tail Lock. See SHEAR LOCK. protection against erosion and scour pr, perhaps, to prevent the accumulation of stream de- Tail Pit. See COUNTERWEIGHT WELL. bris. Tail Water. Water ponded below the outlet of a Toggle Joint. A mechanical arrangement where- culvert, pipe, or bridge waterway, thereby rein two members are hinged together, in fact or

G-42 in effect, at a central location and hinged separately at their opposite ends ; their alignment Transverse Girder. See CROSS GIRDER. forming an obtuse angle so that a force applied Travel Way. See ROADWAY. at the common hinge location will produce a thrust acting at the end hinges, laterally to the Tread Plates. (Roller Tread.) The plates attached upon the bottom flange of the drum gir- alignment or direction of the original force. der; shaped to form a circular surface taking a Tolerance. (Margin.) A range or variation in uniform even bearing upon the drum rollers physical or chemical properties specified or oth- and thereby transferring to them. the live and erwisedeterminedaspermissiblefor the dead loads of the superimposed structure. The acceptance and use of construction materials. assemblage of tread plates is sometimes described as the "Upper Track." Tower.1.. A threedimensionsubstructure framework in a viaduct type structure having Tremie. A long trunk or pipe used to place con- the vertical bents at its ends joined longitudi- crete under water. A tremie usually has a hop- nally by struts and braces thus rendering the per at,its upper end. assemblage so formed effectivein resisting forces acting longitudinally upon the structure. The concrete placed under water by use of a 2. A four-sided frame supporting the ends of tremie is often called tremie concrete. In plac- two spans or instead one complete span (tower ing tremie concrete, it is important that the span) ,and the ends of two adjacent spans of a mouth of the tremie be kept immersed within viaduct ; having its column members strutted the mass of concrete already deposited to pre- and braced in tiers and the planes of either two vent the water from mixing with the concrete, or four sides battered. 3. A pier or a frame thereby weakening or destroying it. serving to support the cables or chains of a sus- Trestle: A bridge structure consisting of beam, pension type bridge at the end of a span. 4. A girder or truss spans supported upon bents. The frame functioning as an end support, guide bents may be of the piled or of the frame type, frame and counterweight support for a vertical composed of timber, reinforced concrete or lift span during an operating cycle. metal. When of framed timbers, metal or rein- Track Girder. See SEGMENTAL GIRDER. forced concrete they may involve two or more tiers in their construction. Trestle structures Track Plate. The plate, toothed or plain, upon aredesignatedas"wooden,""frame,"or which the segmental girder of a rolling lift span "framed," "metal," "concrete," "wooden pile," rolls. "concrete pile," etc., depending upon or corre- Track Segment. One of the assemblage pieces of sponding to the material and characteristics of thecirculartracksupportingthebalance their principal members. wheels of a center bearing swing span or the Trailing Wheel. See BALANCE WHEEL. drum bearing wheels of a drum or combined center and drum bearing span. Triangular Truss. See WARREN TRUSS. Transition Length. The tangent length within Trunnion. As applied to a bascule bridge. The which the change from a normal to a superele- assemblage consisting essentially of a pin fitted vated roadway cross section is developed. into a suppoiting bearing and forming a hinge Transverse Bracing. (Transverse System.) The or axle upon which the movable span swings bracing assemblage engaging the columns of during an opening - closing. cycle. trestle and viaduct bents and towers in perpen- Trunnion Girder. The girder supporting the dicular or slightly inclined planes and in the trunnions on a bascule bridge. horizontal or nearly horizontal planes of their sash braces to function in resisting the trans- T.cuss. A jointed structure having an open built verse forces resulting fr.'m wind, lateral vibra- web construction s(' arranged that the frame is tion and traffic movements tending to produce divided into a series of triangular figures with lateral movement and deformation of the col- itscomponent straight members primarily umns united thereby. See BRACING. stressed axially only. The triangle is the truss

G-43 element and each type of truss used in bridge Uplift. A negative reaction or a force tending to construction is an assemblage of triangles: The lift a beam, truss, pile, or any other bridge ele- connecting pins are assumed to be frictionless. ment upwards.

Truss Bridge. A bridge having a truss for a V superstructure: The ordinary single span rests upon two supports, one at each end, which may Vertical-Lift Bridge. See MOVABLE BRIDGE. be abutments, piers, bents or towers, or combi- Viaduct. A bridge structure consisting of beam, nations thereof. The superstructure span may girder, truss, or arch span supported upon abut- be divided into three parts, viz.: (1) the trusses, ments with towers or alternate towers and (2) the floor system and (3) the bracing. bents or with a series of piers (cylindrical, dumbbell, rectangular or other types), or with Truss Panel. See PANEL. any combination of these types of supporting Trussed Beam. A beam reinforced by one or parts. more rods upon its tension side attached at or In general, a viaduct is regarded as having near its ends and passing beneath a support at greater height than a trestle. However, this no- the midlength of the span producing in effect an tion is inconsistent with bridge engineering inverted King post truss. The support, if a wood- practice. A viaduct may be in all respects like a en block, is commonly termed a "saddle block" multiple span bridge. but, if a cast iron or structural steel member it Vierendeel Truss. A rigid frame consisting es- is termed a "stanchion." sentially of an assemblage of rectangles and Tubular Truss. A truss whose chords and struts trapezoids with no diagonal members. Its serv- are composed of pipes or cylindrical tubes. ice in a bridge is the same as that assigned to a plate girder or a truss. Tudor Arch. See GOTHIC ARCH. Voided Unit. A precast concrete deck unit con- Turnbuckle. A device used to connect the ele- taining cylindrical voids to reduce dead load. ments ,of adjustable rod and bar members. It Voussoir. (Ring Stone.) One of the truncated consists of a forging having nut-like end por- wedge shaped stones composing a ring course in tions right and left hand threaded and inte- a stone arch. The facing or head voussoirs are grally connected by two bars upon its opposite those placed at the Lerminations of a ring sides thus proyiding an intervening open space course. through which a lever may be inserted to adjust the tension in the member. Turning Pinion and Rack. The pinion to which Wale. (Wale-Piece, Waler.) A wooden or metal the power to operate a swing span is applied piece or an assemblage of pieces placed either and the circular rack fixed upon the pivot pier inside or outside, or both inside and outside, upon which the pinion travels to produce its the wall portion of a crib, cofferdam or similar rotation movement. When a swing span re- structure, usually in a horizontal position to quires a very considerable amount of power to maintain its shape and increase its rigidity, sta- operate it, two operating pinions located at op- bility, and strength. An assemblage of wale posite sides of the circular rack or nearly.so are pieces is termed a "waling," or "strake o' wail." commonly used to distribute the operating force upon the rack and its anchorage. Warren Truss. (Triangular Truss.) A parallel chord truss developed for use in metal bridge structures, wherein the web system is usually U fcirrhed by a single triangulation of members at UBolt. A bar, either round or square, bent in an angle to each other. There are no counters the shape of the letter "U" and fitted with but web members near the center of a span may threads and nuts at its ends. be subject to stress reversals and are to be designed accordingly. Verticals-may or may not be Underpass. See OVERPASS. used.

G-44 Washer. A small metal disc having a hole in its Web Plate. The plate forming the web element center to engage a bolt or a rivet. It may be of a plate girder, built-up beam or column. used beneath the nut or the head of a bolt or as a separator between elements of a member or Wedge and Pedestals. An adjustable bearing the members of a structure. device or assemblage consisting of a wedge operating between an upper and a lower bearing Water Table. The upper limit or elevation of block or pedestal, and when installed at each ground water saturating a portion of a soil outermost end of the girders or the trusses of a mass. swing span, functioning to lift them to an ex- Waterway. The available width for the passage tent that their camber or "droop" will be re- of stream, tidal or other water beneath a bridge, moved and the arms rendered free to 'act as if unobstructed by natural formations or by ar- simple spans. Furthermore, when installed be- tificial constructions beneath or closely adjacent neath the loading girder of a center bearing to the structure. For a multiple span bridge the swing span they serve to relieve the pivot available width is the total of the unobstructed bearing from all or nearly all live load and to waterway lengths of the spans. See CLEAR stabilize the center portion of the span. When SPAN. the wedges are withdrawn and the end latching device released, the span is free to be-moved to Wearing Surface. (Wearing Course.) The sur- an "open" position. face portion of a roadway area which is in Lifting devices of the wedge and pedestal direct contact with the means of transport and type may be used under the loading girder ofa is, therefore, primarily subject to the abrading, center bearing swing span in conjunction with crushing or other disintegrating effect pro- rocker and eccentric, link and roller, or other duced by hammering, rolling, sliding or other end lifting devices at the ends of the span. physical action tending to induce attrition thereof. However, some swing spans of short length and placed in rather unimportant locations are A topmost layer or course of material applied designed to support both dead and live loads upon a roadway to receive the traffic service upon the center pivot and the ends of span are loads and to resist the abrading, crushingor indequately lifted with the result that they "end other distintegrating action resulting, there- hammer" upon their pedestals. from. Wedge Stroke. The theoretical travel distancea Web. The portion of a beam, girder or truss, wedge must move upon its pedestal to lift the located between and connected to the flangesor end of the arm of a swing span a distance equal the chords. It s serves mainly to resist shear to the vertical camber or "droop" of the arm stresses. The stem of a dumbbell or solid wall due to elastic deformation minus the portion as- type pier. sumed to be provided in the field erection opera- Web Members. The intermediate members of a tion, truss extending, in general, from chord to chord The actual elastic deformation of the arms of but not including the end posts. Inclined web a given swing span may vary considerably from members are termed diagonals. A "tie" isa the theoretical due probably to temperature diagonal in tension while a brace or strut isa variations during the periods in which fabrica- diagonal in compression. A vertical webmem- tion and erection are in progress, or to varia- ber in compression is commonly designateda tion inthefriction developed between the post, while one in tension due entirely to the elements combined to form joints and to other external forces applied at its lower end, is des- incidental irregularities. ignated a hanger. The joint formed by the in- Weep Hole. (Weep Pipe.) An open hole oran tersection of an inclined end post with the top embedded pipe in a masonry retaining wall, chord is commonly designated the hip jointor abutment, arch or other portion of a masonry "the hip" end and the vertical tension member structure to provide means of drainage for the engaging the hip joint is commonly knownas embankment, causeway, spandrel backfill or re- the hip vertical or the first panel hanger. tained soil wherein water may Accumulate.

G-45 Weld. The process of uniting portions of one or Welded Joint. A joint in which the assembled more pieces, the elements of a member, or the elements and members are united through fu- members of a structure in an intimate and per- sion of metal. The design of a welded joint con- manent position or status by (1) the application templates a proper distribution of the welds to of pressure induced by the blow of a hammer or develop its various parts with relation to the by a pressure machine, the portions to be united stresses and the purpose which each must serve, having been previously heated to a so-called due consideration being given to factors pro- welding temperature and the junction areas/ ductive of secondary stresses through weld cleaned and purified by the application of time' shrinkage, warping and other conditions ating material, or by (2) the use of a high tem- tending weld fabrication. perature flame to preheat the metal adjacent to Wheel Base. A term applied to the axle spacing the weld location and when it has attained a or lengths of vehicles. When applied to automo- molten temperature to add molten weld metal, biles and trucks having wheel concentrations at in conjunction with fluxing material, in suffi- the ends of the front and rear axles it is the cient quantity to produce a fully filled joint length center to center of axles or the longitudi- when cooled or by (3) the use of the electric arc nal dimension center to center of front and rear to obtain a molten temperature in the metal wheels. closely adjacent to the weld location and to supply in the arc stream molten filler metal and Wheel Concentration. (Wheel Load.) The load fluxing material requisite to produce by coalesc- carried by and transmitted to the supporting ence of the structure and electrcde metals a structure by one wheel. This concentration may fully filled joint. involve the wheel of a traffic vehicle, a movable The joint produced by the apprcation of a bridge, or other motive equipment or device. welding process. See AXLE LOAD. Wheel Guard. (Fit loe Guard.) A timber piece Weld Layer. A single thickness of weld metal placed longitudinally along the side limit of the composed of beads (runs) laid in contact to roadway to guide' the movements of vehicle form a pad weld or a portion of a weld made up wheels and safeguard the bridge trusses, rail- of superimposed beads. ings and other constructions existing outside Weld Metal. The fused filler metal which is the roadway limit from collision with vehicles added to the fused structure metal to produce and their loads. by coalescence and interdiffusiona welded Whiteway Lighting. The lighting provided for joint or a weld layer. nighttime illumination along a road or bridge, Weld Penetration. The depth beneath the origi- as distinguished from sign lighting or colored nal surface, to which the structure metal has regulatory and warning lights. been fused in the making of a fusion weld. See Wide Flange. (Carnegie Beam.) A rollf.d mem- PENETRATION. ber having an H-shaped cross section, differentiated from an I-beam in that the flanges are Weld Sequence. The order of succession re- wider and the web thinner. quired for making the welds of a built-up piece or the joints of a structure to avoid, so far as Wind Bracing. The bracing systelas in girder practicable, the residual stresses producing or and truss spans and in towers and bents which tending to produce individual joint distortions function to resist the stresses induced.by wind and deformations of the structure or its mem- forces. bers. Wing Wall. The retaining wall extension of an Welded Bridge. (Welded Structure.) A struc- abutment intended to restrain and hold in place ture wherein the metal elements composing its the side slope material of an approach causeway. members and the joints whereby these members or embankment. When flared at an angle with are combined into the structure frame, are the breast wall it serves also to deflect stream united by welds. water and floating debris into the waterway of

G-46 the bridge and thus protects the approach em- wall is usually a continuation of the base por- bankment against erosion. The general forms of tion of the breast wall but may be stepped to a wing walls are : higher or lower elevation to obtain acceptable (1) Straightin continuation of the breast foundation conditions. wall of the abutment. A stub type of straight wing wall is sometimes used in connection with a pier-like or (2) U-typeplaced parallel to the alignment bent-iike abutment placed within the end of an of the approach roadway. embankment. This type, commonly known as "(3) Flaredforming an angle with the align- "elephant ear" or as "butterfly wing" serves to ment of the abutment breast wall by receding retain the top portion of the embankment from therefrom. about the elevation of the bridge seat upward to (4) Curvedforming either a convex or the roadway elevation. The top surface is bat- concave arc flaring from the alignment of the tered to conform with the embankment side abutment breast wall. slope. The footing of a full abutment height wing Working Stress. See STRESS.

G-47 BIBLIOGRAPHY General and Historical Wright, D. T. Evaluation of highway bridges, Allen, R. S. Covered bridges. Brattleboro, Ver- Highway Research Board Proceedings, 195'i, 146-174. mont : Greene, 1957. ASCE Transactions, Volume CT. New York : Materials ASCE Publications, 1953. Feld,J.Construction failures. New York : Aston, J. and Story, E. Wrought iron. Pitts- Wiley, 1968. burgh : Myers Company, 1939. Jacobs and Neville. Bridges, canals, and tun- Byers Company. The ABC's of wrought iron. nels. New York : Van Nostrand, 1968. Pittsburgh :Byers Company. Steinman, D. B. and Watson, S. Bridges and Hunt, G. and Garratt, G. W.od preservation. their builders. New York: Dover, 1957. New York : McGraw-Hill, 1953. Tyrrell, H. G. History of bridge engineering. Troxell, G. and Davis, H. Concrete. New York: 1st ed., 1911. McGraw-Hill, 1956. Waddell, J. A. L. De Pontibus. New York: U.S. Department of Agriculture. Wood hand- Wiley, 1905. book. Washington, D. C., 1955. Whitney, C. S. Bridges. New York: Rudge, West Coast Lumberman's Association. Douglas 1929. fir use book. Portland, Oregon : Daily Journal of Commerce, 1958. Structural Analysis and Design Withey, M. 0. and Washa, G. W. Materials of Beedle, L., et al. Structural steel design. New construction. New York: Wiley, 1954. York: Ronald, 1964. Cissel, J. H. Stress analysis and design of ele- Handbooks and Specifications mentary structures. New York : Wiley, 1948. Aluminum Association. Aluminum construction. Grinter, L. Design of modern steel structures. manual. New York :Aluminum Association, New York: MacMillan, 1941. 1957. Grinter, L. Theory of modern steel structures, Aluminum CompanyofAmerica.AT,COA Volume I. New York : MacMillan, 1962. structural handbook. Pittsburgh :Aluminum Hansen, R. Modern timber design. New York : Company of America. Wiley, 1948. AmericanAssociationofStateHighway Jensen, A. Applied strength of materials. New Officials. Standard specifications for highway York: McGraw=Hill, 1957. bridges. Washington, D.C.: American Associa- tion of State Highway Officials, 1969. Lin, T. Y. Prestressed concrete design. New York : Wiley, 1955. AmericanAssociationofStateHighway Officials.Specifications for movable bridges. McLean and Nelson. Engineering mechanics. Washington, D.C.: American Association of New York : McGraw-Hill (Schaum). State Highway Officials, 1970. Nash, W. A. Strengths of materials. New York : American Concrete Institute. Reinforced con- McGraw-Hill (Schaum), 1957. crete design handbook (working stress). SP-3, Sutherland, H. and Reese, R. Reinforced con- 2nd edition. Detroit: American Concrete Insti- crete design. New York: Wiley, 1943. tute, 1955.

B-1 American Institute of Steel Construction, Steel nance practice. Sacramento : California Depart- construction manual, 6th edition, New York : ment of Public Works, 1945. American Institute of Steel Construction, 1963. biers, H. Bridge maintenance. Proceedinn An- AmericanWoodPreservers' ssoci ati on. nual Road ; School, Purdue University, 1965, AWPA manual. Washington, D.C.: erican 22-27. Wood Preservers' Association, 1964. Johnson, S. M. Deterioration, maintenance, and AmericanWood Preservers' Association. repairs of structures. New York: McGraw-Hill, AWPA standards. Washington, D.C. : Ameri- 1965. can Wood Preservers' Association, 1965. American Welding Society. Specifications for McGovern, J. F. Maintenance of structures. welded highway and railroad bridges. New Proceedings Massachusetts Highway Confer- York : American Welding Society, 1969. ence, 1961,.63-72. American Welding Society. Welding handbook. Rogers, T. WI. Bridge maintenance practice New York : American Welding Society, 1962. (California). Proceedings Highway Research Board, 1953, 30, 355-363. Gaylord, E. H., Jr. and. Gaylord, C. N. Struc- turalengineeringhandbook.New York : Wilcox, H. N. Bridge maintenance practice. McGraw-Hill, 1968. Yearbook, American Public Works Association, Seelye, E. E. Data book for civil engineers, Vol- 1960, 221-226. ume III. New York : Wiley, 1947. Testing Maintenance and Repairs Department of Transportation and Bethlehem Aherne, J. J., Jr. Maintaining capacity of town Steel Corporation. Ultra-sonic testing inspec- bridges. Proceedings Massachusetts Highway ticn for butt welds in highway and railway Conference, 1962, 1-6. bridges. AmericanAssociationofStateHighway McGonnagle, W. J. Non-destructive testing. Officials. An informational guide for mainte- New York : McGraw-Hill, 1961. nance inspectors. Washington, D. C.: American Association of State Highway Officials, 1964. National Cooperative Highway Research Projects AmericanAssociationofStateHighway Highway Reserach Board. Bridge deck durabil- Officials. Construction manual for bridges and ity. Project 20-5, Topic 3. incidentalstructures.Washington,D.C.: AmericanAssociationofStateHighway Highway Research Board. Bridge approach de- Officials, 1966. sign and construction practice. Project 20-5, Topic 2. American'AssociationofStateHighway Officials. Manual for maintenance inspection of Movable Bridges bridges. Washington, D.C.: American Associa- tion of State HighWay Officials, 1970. Abbett. American civil engineering practice, Army Department. Principlesofbridging. Volume III. New York : Wiley, 1957. Army. Department TM-5-260,1955. 'Army Cortelyou, F. E. Proceedings American Bridge (War) Department. Roads, runways, and mis- Tunnel and Turnpike Association, 1949, pp. cellaneous pavements, repairs, and utilities. 34-43. Army Department TM-5-624, May 1947. Hoole, G: A. and Kinne, W. S. Movable and Birch, W. D. Organization and operation of a long span bridges. New York : Wiley, 1923. bridgemaintenanceprogram.Proceedings Canadian Good Roads Association, 1961, 249- Hovey, 0. E. Movable bridges, Volumes I and 262. II. New York : Wiley, 1926. California Department of Public Works, Divi- Illinois Division of Waterways. Annual Re- sion of Highways. California bridge mainte- ports, 1955-1958.

B-2 Paul, A. A. Repairs to rolling lift bridges over print #6-1952, Purdue Engineering Experi- River Lee at Cork. Paper #123. Institute of ment Station, Lafayette, Ind. Civil Engineers, 1932, London, England. Steinman, D. B. Suspension bridges. New York: Ruble, E. J. and AAR staff. Results of field tests Wiley, 1929. on bascule bridges. Structural Engineering Re-

B-3 INDEX

Paragraph Page Paragraph Page Abutment 5-8 5-25 Cracking 4-2.3f (2) 4-4 4- 2.3g(1)4-4 ' Aerial obstruction lights 5-31.4 5-101 5-31.5f. 5-107 5-1.4b. 5-4 Aluminum 5-6 5-18 5-2.4b. 5-10 Anisotropy 5-1.2g. 5-2 5-6.2a. 5-18 5-3 lc. 5-11 Crib wall 5-9.1b. 5-29 Approaches 5-23 5-78 5-9.2c. 5-30 Arch bridge 2-1.3 2-2 Cross frame-- 2- 2.2c(4) 2-11 5-16 5-53 Beams 5-12 5-37 Culverts, box 5-27 5-93 5-13 5-41 5-14.1 5-44 Deck 2-2.2c (1) 2-10 Box 5-12.2c. 5-38 Decks 5-20 5-69 Calculations 2-3.4 2-17 Concrete 5-20.2a. 5-70 Concrete 5-12.2a. 5-37 Open grating 5-20.2d. 5-11 Concrete T 5-12.1 5-37 Steel 5-20.2c. 5-71 5-14.2b. 5-45 Timber 5-20.2b. -5-71 Floor 5-14.2a. 5-44 Deflection 5-10.21. 5-31 5-14.3a. 5-45 Pile caps 5- 11.2b(4)5-34 I-Beam 5-12.1 5-37 Concrete beams 5- 12.2a(6)5-38 Prestressed concrete ______5-12.2e. 5 -38' Steel beams 5-13.2h. 5-43 5-14.2b. 5-45 5-17.2g. 5-56 Steel 5-13.1 5-41 Timber decks 5- 20.2b(2)5-71 Timber 5-14.2b. 5-45 Bascule spans 5- 32.3c(1)5-115 Voided units 5-12.1 5-37 Diagrams, shear and moment 2-3.4e. 2-21 5-12.2c. 5-38 Diaphragm 5-16 5-53 Bearings 2- 2.2c(5)2-11 Distress, movable bridges 5-32.2 5-110 4-2.3m. 4-6 Diver 5-33.3 5-118 Elastomeric pad 5-19 5-66 Dolphin types 5-25.1a. 5-81 Metal 5-18 5-60 Drainage, bridge 5-24 5-80 5-19 Bearing failures 5-7.3b. Elasticity 5-1.2e. 5-2 Bents, general 5-10 5-30 Elastoineric pad bearings 5-19 5-66 Pile 5-11 5-34 Elements of bridges 2-2 2-10 5-24 Bents, underwater investigation of5-7.5m. Expansion joint 5-21 5-71 Box culverts 5-27 5-93 Eyebars 4-2.3a. 4-2 Box girder 5-15.1b. 5-48 Concrete 5-12.2b. 5-38 5-15.2a. 5-48 Steel 2-1.6c. 2-3 5- 34.1b(3)5-119 2-1.6f. 2-7 5-13.1 5-41 Fenders, general .5 -25 5-81 Bracing______2- 2.2c(4)2-11 Fender types 5-25.1b.. 5-81 5-17 5-55 Forms, inspection 3-5 3-11 Bridge drainage 5-24 5-80 Foundation movements 5-7 5-18 Bridge elements 2-2 2-10 Frame Bridge forces 2-3.2 2-12 Cross 5-16 5-53 Bridge site organization 1-2.2 1-3 Sway 5-17 5-55 Bridge types 2-1 2-1 Fungus decay 5-3.3a. 5-11 Calculations 2-3.4 2-17 Girders 5-12 5-37 Cast iron 5-4 5-16 5-13 5-41 Cast iron bridge __ 2-1.4 2-2 Concrete box 5-12.2b. 5-...3.3 Clapper bridge 2-1.2 2-1 Steel box 2-1.6c. 2-3 Compression ______2-3.3h. 2-14 2-1.6f. 2-7 Concrete 5-1 5-2 5-13.1 5-41 Paragraph Page . Paragraph Page Hangers 5-13.2i. 5-43 Piling, underwater investigating of 5-7.5m. 5-24 Hangers, safety (in confined spaces)1-2.6b. 1-5 5-33.2. 5-118 Hinges 5-13.2i. 5-43 Pins 4-2.3d. 4-4 Inspection 4-2.3f. 4-4 Notebook, preparing the 3-2 3-2 5-13.2a. 5-41 Planning 3-2.3 3-2 5-15.1b. 5-48 Procedures, sequence of 4-1 4-1 5-15.2a. 5-48 Procedures, systematic 4-2 4-2 5-18.2a. 5-60 5-62 Recommendations 6-2 6-2 5-18.21. Reporting 3-2.3 3-2 Planning, inspection 3-2.3 3-2 Reports 6-1 6-1 Pop outs 5-1.4e. 5-8 Scheduling 3-2.2 3-2 Portals 5-17.1b. 5-55 3-2.3b. 3-2 Prestressed concrete bridge (beams)5-12.2c. 5-38 Types 3-2.1 3-2 Procedures, inspection 3 -2.3c. 3-3 Sequence 4-1 4-1 Inspector, duties of the 1-1.3 1-1 Systematic 4-2 4-2 Inspector qualifications 1-1.2 1-1 Procedures, safety 1-2.6c. 1-5 1-1.2 1-1 Joint,expansion 5-21 5-71 Qualifications, inspector Jointspell 5-1.4d. 5-8 Reactions 2-3.4b. 2-17 Recommendations Lateral bracing 5-17.1b (2)5-55 Categories of repair 6-2.2 6-2 Lighting 5 -31 5-100 Cost consideratian3 6-2.3 6-2 Limnoria 5- 3.36(4) 5-14 Priorities 6-2.4 6-4 Log bridge 2-1.1 2-1 Reinforced concrete bridges 2-1.6d. 2-5 Marine borers '55-3.3b (4) 5-14 Repairs, categories of 6-2.2 6-2 5-5.3f. 5-17 Reports Mechanics 2-3 2-12 General 6-1.2a. 6-1 Metal bearings 5-18 5-60 Inspection 6-1 6-1 Moment, diagrams 2-3.4e. 2-21 6-1.26. 6-1 Moments 2-3.3d. Objectives 2-16 . Uses 6-1.3 6-1 2-3.4d. 2-21 5-9 5-29 Movable bridges Retaining wall 2-1.7 2-7 Rotational forces (moments) ____ _ 2-3.3d. 2-1( 5-32 5-107 Rust 5-2.4a. 5-9 Bascule 5-32.1b. 5-108 Swing 5-32.1a. 5-107 Safety 1-2 1-2 Types of distress 5-32.2 5-110 Safety procedures 1-2.6c. 1-5 Vertical lift , 5-32.1c. 5-110 Scaling . Warning devices 5-32.3a (5)5-114 Scheduling, inspection 53--21.2". 5-33-2 Movements, magnitude of founds- 3-2.3b. 3-2 tion 5-7.4a. 5-21 Scour 5-26.1a. 5-84 Mudballs 5-1.4f. 5-8 5-26.2e. 5-87 Seepage 5-7.3d. 5-19 Notebook, inspection 3-3 3-3 Settlements Paint 5-?S 5 -95. Differential 5-7.4b(2)5-22 Pier 5-10 5-30 Uniform 5-7.4b(1)5-22 Pile bents 5-11 5-34 Signing 5-29 5-96 Piles 4-2.6 4-7 Sign types 5-29.2a. 5-96 Concrete 5-25.3b. 5-84 Simple beam, simple span_ 2-1.6c. 2-3 Prestressed concrete 5-7.5m. 5-24 2-3.3d. 2-16 5- 33.2a(3)5-118 Shear 2-3.3c. 2-14 Steel 5-10.2h. 5-31 2-3.4c. 2-19 5-11.2c. 5-35 Shear and moment diagrams 2-3.4e. 2-21 5-25.3a. 5-84 Spalling 5-1.4c. 5-6 5-33.2a(1)5-118 5 -5.4b. 5-17 Timber 5-11.2b. 5-34 Steel 5-2 5-8 5-25.3e. 5-84 Steel bridges 2-1.6a. 2-3 5-33.2a(2)5-118 Steel girders 5 -13 5-41 Pile defects 5-7.3k. 5-2 Stone masonry 5-5 5-17 L Pile settlement 5 -7.2c. 5-18 Stream bed degradation 5-26.1b. 5-85 5-7.2j. 5-20 Stress 2-3.3 2-13 1-2 ParagraphPage ParagraphPage 0" Underwater investigation 4-2.6 4-7 Stress concentrations 5-2.4d. 5-11 5-33 5-117 Stringer 5-14.2b. 5-45 Utilities 5-30 5-99 5-14.3b. 5-45 Structure evaluation 3-4 3-8 Vertical shear 2-3.4c. 2-19 Suspension bridges______2-1.8 2-7 Vibration 5-10.21. 5-31 5-34 6-119 5- 12.2a(6)5-38 Sway frame 5-17.1b. 5-56 - 5-13.2h. 5-43 6-17.2g. 5-56 5- 32.3c(1)5-115 Tension 2-3.3a. 2-13 Tere do 5- 3.3b(4)5-14 Warning devices, movable bridges _ 5- 32.3a(5)5-114 Termites 5- 3.3b(1)5-14 Water table variations ______5-7.3e. 5-19 Timber 5-3 5-11 Waterway adequacy 5-26.1c. 5-85 Tools and equipment 1-1.4 1-2 Waterways 5-26 5-84 Trusses 2-1.5 2-3 Weathering 2-1.6b. 2-3 0 i timbers 6-3.2c. 5-11 5-15 5-48 Of stone 5 -5.4a. 5-17 Steel 5-15.2a. 5-48 Wing wall 5-9.1a. 5-29 Timber 5-15.2b. 5-50 Wrought iron 5-4 5-16

1-3 *E. S. GOVERNMENT PRINTING OFFICE: I 972 0 -462 - 930