The same eastbound movement from Rockland crosses 1.19 (miles west of Hollins) over Jones Falls. This bridge was originally no. 1 on the Green Spring Branch in the Northern Central numbering scheme. PHOTO BY MARTIN K VAN HORN, MARCH 1961 /COLLECTION OF ROBERT L. WILLIAMS.

On October 21, 1959, the Interstate Commerce maximum extent. William Gill, later involved in the Commission gave notice in its Finance Docket No. streetcar museum at Lake Roland, worked on the 20678 that the Green Spring track west of Rockland scrapping of the upper branch and said his boss kept would be abandoned on December 18, 1959. This did saying; "Where's all the ?" Another Baltimore not really affect any operations on the Green Spring railfan, Mark Topper, worked for Phillips on the Branch. Infrequently, a locomotive and a boxcar would removal of the bridge over Park Heights Avenue as a continue to make the trip from Hollins to the Rockland teenager for a summer job. By the autumn of 1960, Team Track and return. the track through the valley was just a sad but fond No train was dispatched to pull the rail from the memory. Green Spring Valley. The steel was sold in place to the The operation between Hollins and Rockland con- scrapper, the Phillips Construction Company of tinued for another 11/2 years and then just faded away. Timonium, and their crews worked from trucks on ad- So far as is known, no formal abandonment procedure jacent roads. Apparently, Phillips based their bid for was carried out, and no permission to abandon was the job on old charts that showed the trackage at its ' obtained.

Green Spring Branch • 87

f34-1748 STEEL BRIDGE, GREEN SPRING BRANCH, NCRR - 1900-1925 - At rail crossing of Jones Falls, Robert E. Lee Park. Plate bridge on granite abutments, a survival of the Baltimore and Susquehanna Rail Road route to Owings Mills (1831), later the route of the Western Maryland, and still later the Valley Branch of the Northern Central; service terminated in 1959. Now inside city-owned park surrounding Lake Roland. Ties provide a foot crossing (1977).

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E O U.S. DEPARTMENT OFTHE I ai4

A BULFINCH PRESS BOOK James Millholland (1812-1875), railway master mechanic, is particularly well known for his invention of many railway mechanisms. His association with the Philadelphia and Reading Railroad Company as master machinist spanned fifty years in the early development of the American railroad. He also founded the locomotive shops at Mt. Savage, Maryland, the center of the Cumberland and Pennsylvania Railroad. Millholland's inventions and contributions include the cast- crank axle, wooden spring, plate , poppet throttle, anthracite firebox, water grate, drop frame, and steel tires. He was also an early user and advocate of the superheater, the feedwater heater, and the injector. Several of his innovations were adopted as standard practice by the railroad industry. His son, James A. Millholland, was a railroad executive.

References • White, John H. "James Millholland and Early Railroad Engineering". Contributions From the Museum of History and Technology #252 (1968): 3-36.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

A is a bridge supported by two or more plate . The plate girders are typically I-beams made up from separate plates (rather than rolled as a single cross- section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the . In some cases, the plate girders may be formed in a Z-shape rather than I-shape. The first tubular wrought iron plate girder bridge was built in 1846-47 by James Millholland for the Baltimore and Ohio Railroad.11.1 Plate girder bridges are suitable for short to medium spans and may support railroads, highways or other traffic. Plate girders are usually prefabricated, and the length limit is frequently set by the mode of transportation used to move the girder from the bridge shop to the bridge site. j2],

Anatomy of a plate girder. Generally, the depth of the girder is no less than 1/15 the span, and for a given load bearing capacity, a depth of around 1/12 the span minimizes the weight of the girder. Stresses on the flanges near the center of the span are greater than near the end of the span, so the top and bottom flange plates are frequently reinforced in the middle portion of the span. Vertical stiffeners prevent the web plate from buckling under shear stresses. These are typically uniformly spaced along the girder with additional stiffeners over the supports and wherever the bridge supports concentrated loads. 01 ▪▪

Deck-type plate girder bridge In the -type bridge, a , steel or reinforced bridge deck is supported on top of two or more plate girders, and may act compositely with them. In the case of railroad bridges, the railroad ties themselves may form the bridge deck, or the deck may support ballast on which the track is laid. Additional beams may span across between the main girders, for example in the form of bridge known as ladder-deck construction. Also, further elements may be attached to provide cross-bracing and prevent the girders from buckling.

Half-through plate girder bridge

P late girder bridge: half-through type. In the half-through bridge, the bridge deck is supported between two plate girders, often on top of the bottom flange. The overall bridge then has a 'U'-shape in cross-section. As cross-bracing cannot normally be added, vertical stiffeners on the girders are normally used to prevent buckling (technically described as 'U-frame behaviour'). This form of bridge is most often used on railroads as the construction depth (distance between the underside of the vehicle, and the underside of the bridge) is much less. This allows obstacles to be cleared with less change in height.

Multi-span plate girder bridge

M ultispan Plate girder bridge: deck type on concrete piers. Multispan plate-girder bridges may be an economical way to span gaps longer than can be spanned by a single girder. Piers serve as intermediate abutments between the end Abutments of bridge. Separate plate girder bridges span between each pair of abutments in order to allow for expansion joints between the spans. Concrete is commonly used for low piers, while steel trestle work may be used for high bridges.

References

1. A Henry Grattan Tyrrell, History of Bridge Engineering, Williams, Chicago, 1911; page 195. 2. A J. A. L. Waddell, Bridge Engineering Vol. 1, Wiley, New York, 1916; page 409. 3. A The Building Trades Handbook, 3rd Ed., International Textbook Company, Scranton, 1914, pages 106-107.

See also Wikimedia Commons has media related to: Plate girder bridges • - the ancestor of the plate girder bridge • bridge - an evolution of the plate girder bridge • Trestle - some modern steel trestles are composed of a number of girder bridge segments. • Pin and hanger assembly DESIGN OF STEEL STRUCTURES

BY LEONARD CHURCH URQUHART, C. E. Professor in Charge of , Cornell University

Books by AND L. C. URQUHART CHARLES EDWARD O'ROURKE, C. E. AND Assistant Professor of Structural Engineering, C. E. O'ROURKE Cornell University DESIGN OF CONCRETE STRUCTURES TABLES AND DIAGRAMS FROM DESIGN OF CONCRETE STRUCTURES STRESSES IN SIMPLE STRUCTURES DESIGN OF STEEL STRUCTURES

FIRST EDITION SECOND IMPRESSION

MCGRAW-HILL BOOK COMPANY, INC. NEW YORK AND LONDON 1930 PLATE GIRDER BRIDGES 105

riveted to the outstanding legs of the angles, as shown in Fig. 64b. When the required number of cover plates becomes excessive, the form of b may be modified as shown in c and d. The maximum bridge span to which the plate girder is adapted CHAPTER V is about 135 ft., and unless the depth is unduly limited, sections PLATE GIRDER BRIDGES' such as are shown in b or c will usually furnish sufficient flange material. The section -shown in d is relatively uneconomical 55. General Forms of Plate Girders. For spans in excess because of the extra riveting and the lowering of the center of of 25 ft., the relatively large depth of beam required to carry gravity of the flange material which results in a decreased effective normal railway or loads prohibits the use of rolled depth of the girder. sections. In order to secure the necessary depth and yet main- Very often, in building construction, the depth of a beam or tain the economy of the I-beam section, a built-up beam of girder is limited to a value which is far below the economical similar cross-section may be used. A built-up beam, in which depth. In some such cases, girders of the forms illustrated in

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FIG. 65. Fig. 64 will not provide the necessary cross-section. By using 1 two or more webs this difficulty may be overcome. Figure 1 65 illustrates two common forms of girders that might be used (b) c) (d) (a in such instances. Girders of this type are commonly called FIG. 64. "box girders." the flanges are composed of an assemblage of rolled shapes 56. Plate Girder Bridges. Plate girder bridges are used to (usually plates and angles) riveted to a solid web plate, is called carry both railway and highway loads, and may be either of the a "plate girder." The economy of such a section results from deck or through type. having the flange material as far from the neutral axis as practical, Deck Bridges. In deck railway bridges with open floors, the and making the web only sufficiently thick fully to provide for ties usually rest directly upon the upper flanges of the girders; the shearing stresses. if the floor is to be of the solid ballasted type, or if the bridge The simplest form of plate girder is one which consists of a is to support highway loads, the slab, which may be of wood, web plate to which are riveted four angles, two at either edge concrete, or steel, is placed on top of the upper flanges. The of the web plate and on opposite faces, as shown in Fig. 64a. main girders are connected at intervals by transverse frames If sufficient flange material cannot be provided with this simple in a vertical plane, and the upper flanges are further braced section, additional material may be added in the form of plates, by diagonal bracing in a horizontal plane. Similar lateral All specifications referred to in this Chapter are those of the A.R.E.A., bracing is sometimes placed in the plane of the lower flanges, 1925 (see App. B). but usually the cross-frames are depended upon for the lateral 104 106 DESIGN OF STEEL STRUCTURES PLATE GIRDER BRIDGES 107 support of these flanges. In all but very shallow girders, the web plate is stiffened more or less at regular intervals, by vertical angles, riveted in pairs to the web plate, one on the inside and one on the outside face. Stiffener angles are also provided at each end of the span to transfer the load to the abutments. Deck girders should be spaced, center to center, not less than A5 of the span, and preferably not less than 342 of the span. In order to provide sufficient resistance against overturning,

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it is advisable to specify a minimum limit equal to the depth hra in of the girder. In railway bridges, two girders are necessary :t Ma Pla .

for each track; in highway bridges, the number of girders depends ,er

upon the span, the width of roadway, limitations in depth caused Lo by clearance requirements, and the type of floor. The general arrangement of a deck plate girder railway bridge with open floor is shown in Fig. 66. Through Bridges. In through bridges, the floor system is most

generally supported upon longitudinal stringers, which may be either rolled I-beams or built-up girders; the stringers in turn — are framed into floor-beams, and the floor-beams are riveted to the webs of the main girders, as shown in Fig. 67. As a - 108 DESIGN OF STEEL STRUCTURES PLATE GIRDER BRIDGES 109 general rule, in railway bridges, two stringers are used for each E-60. In highway bridges the spacing is dependent upon the track, one approximately under each rail. If the load is unusu- width of roadway required; sidewalks are generally supported ally heavy, if the stringer span is comparatively long, or if the on brackets outside of the girders. stringer depth is unduly limited, four stringers per track may be necessary. In highway bridges a greater number of stringers is used, the spacing depending upon the type of floor and the class of live load for which the bridge is intended. In some rail- way bridges, where a solid ballasted floor is used, the stringers are omitted and the floor slab is designed to carry the load directly to the floor-beams. This latter arrangement is also frequently used in highway bridges. As in bridges, the live load and the floor load in through plate girder bridges with floor-beams are carried to the main girders at definite points, called panel points. Due to the ease of fastening the floor-beams to the main girders, the panel lengths of plate girder bridges are made relatively short, usually from 12 to 16 ft. The shorter panel length results in a more economical Waterproofing Ba//a51 Tie Rai4 design for the stringers and floor-beams than would be the case if longer lengths were used. wit.44114.,* In narrow railway bridges carrying light loads, the ties may :$1 4140,116M0 rest directly upon the lower flange angles, or upon shelf angles placed at any point above the lower flange angles. Highway floors and solid floors for ballasted railway tracks may be sup- ported in the same manner. Typical sections of such con- structions are shown in Fig. 68. A lower lateral bracing system is used, and the upper flanges Waterproofing are braced by means of triangular gusset plates or knee braces Ballast Tie Rail which are rigidly attached to the floor-beams or floor slab, and which extend to the upper flange section as shown in Fig. 67. Stiffeners are also provided to prevent buckling of the web as in the deck bridges. These are riveted to the web plate, in pairs, at the panel points, to provide a means of connection between the gusset plates and the web, and at other intermediate FIG. 68. points as may be required. End stiffeners are also used to transfer the load to the end bearings. 57. Moments and Shears. A plate girder, whether stringer, The spacing of the girders for through railway bridges is floor-beam, or main girder, is essentially a beam. The first generally fixed by the clearance requirements, a minimum of step toward the design of a girder, therefore, is the determination about 17 ft.-0 in. being necessary for loads equivaleht to Cooper's of the maximum moments and shears, including those due to SUPERSTRUCTURES 461 preference of American designers. For the -pur- If each of the carrying numbers as a whole is fabri- pose of increasing the rigidity_ of the cable and dis- cated from several rolled sections the designation tributing the loads at the points of suspension, a of "girder" is used. series of , known as "stiffening trusses", is Beams for use in bridge construction, rolled with ordinarily appended to each of the main carry- a transverse cross-section roughly corresponding to ing cables. The hangers, or vertical members by the shape of the letter "I", and designated at "I" which the floor system is attached to the main sup-. beams, are familiar to all users of structural mem- porting cables, are also made of wire or eye bar bers. Such beams are made in various sizes and

I

Elevation and Cross Section of a Double Track Through Girder Span links, practice in this respect usually being made sections, and may be used for spans up to a maxi- to harmonize with the character of the main cables. mum of 30 ft. Not less than two beams per rail The towers may be of masonry, steel or concrete. should be used, and considerations of space render As an expedient for spanning large openings, the the use of more than four beams per rail practically preceded the type, by impossible. The beams comprising the group under which it has in a large measure been superseded for each rail should be connected by means of riveted railroad purposes, because of the greater stiffness separators spaced not more than three feet apart, and rigidity afforded by the cantilever design. For and the two groups composing a span should be bridges limited to highway or pedestrian movement, united by lateral bracing. the suspension type is serviceable and economical, Plate girders, under ordinary conditions, repre- where broad openings are to be crossed. Experience sent the most desirable type of construction for indicates that it lacks the rigidity desirable in a spans from 30 to 100 ft. in length, although in some structure designed to support railroad- traffic, par- ticularly with the heavy motive power and rolling equipment current in this day. It is only fair to state, however, that this view is vigorously opposed by some authorities, who maintain that bridges of the suspension type can be made adaptable to con- temporary railroad needs. The anchorage ordinarily consists, as in the case of the , of an "I" beam grillage, heavily encased in masonry or concrete, and deeply buried in the ground. Deck Plate Girders on Stone Masonry Abutments GIRDER BRIDGES Bridges in which the load is carried by means of cases this type of construction has been adapted to metallic units spanning the gap between two sup- spans considerably exceeding the latter figure. Girder ports constitute an important class, comprisino. the construction comprises the through and deck types, two general. types respectively defined as "beam" the track in the former case passing between the and "girder" structures. If the supporting members girders, and in the latter resting upon the top are homogeneous bodies of metal, rolled in their en- flanges. The deck type of construction provides tirety, the structure is designated as a beam bridge. the maximum lattitude, so far as clearance condi- tions are concerned, and, purely from the stand- point of the railroad is the more desirable. However,

Deck Plate Girders on Concrete Piers Through Girders Supported on Cylinder Piers 462 SUPERSTRUCTURES

waterway conditions at stream crossings and clear- or emergency repairs ; an adequate supply should be ance considerations on streets or other thoroughfares held available in railroad stock, and those salvaged frequently preclude the use of deck girders. in good condition from dismantled structures should The forces to be considered in girder design are, be stored for re-use. Girders also have a wide in general, relatively simple and determinate, shear range of adaptability to re-use, and it is frequently being primarily resisted by the webs or vertical sec- found that an old span removed from main line tions, and bending moment by the flanges, or angles track is suitable for re-erection on a branch line, either in its existing condition or with slight modi- attached to the top and bottom of the web. Plate fications. Second-hand girders should not be girder design, including the thickness and depth of scrapped unless it is clearly evident that they are web, and character of flanges, is varied to suit local unsuited to further use. conditions. In the lightest type, each flange con- From the standpoint of railroad operation, the sists of two angles ; in the heavier types the flanges deck type is preferable, in view of the practical elim- are reinforced by the introduction of vertical or ination of clearance considerations, but the adoption horizontal flange plates. of a through design is frequently dictated by water- "I" beams are peculiarly adaptable to maintenance way or other local considerations.

Legend No Description Web plate B Top fl j. angle 3 Bottom fly angle 4 Top cover plate • Bottom cover pl 6 End stiff angle 7 In/ stiff angle 8 Splice plates Top Plan 9 fill. 10 Top pin shoe II Pin

461

,-... Se ction IP Bottom pin shoe Li Roller nest 14 Roller bed plate IS Sole plate 16 Masonry plate 17 Anchor bolt 18 End crass frame 19 Int. cross frame 20 Hot cross flume( 8/ Diag. crass ?Camel 22 Gusset plate Z3 Top laLL erred dottorn Plan and Se ction 24 Bottom lat tattoo! Sc Top lot plate 26 Bottom inf Ode 27 Pedestal Names of Members in Deck Plate Girder Spans

Legend No Description I Web plate 2 Top flange angle 3 Bottom flange angle 8 Splice plates 18 End cross frame 24 lateral angle or rod 26 Lateral plate 28 Main girder 29 floor beam 0 0 30 Int. stringer 31 End stringer Is' Pane/ Pa Panel 0 32 Floor beam bracket 33 Stringerpedistal 34 End of strut End Stringer Pedestal 35 Connection angle III 36 Shelf angle _ Im Note:- for names of parts not numbered compare Names of members in deck _[1.1a 1W4411111, plate girder .spans" aTilTAINFAW Top P an and Section Names of Members in Through Plate Girder Spans

SUPERSTRUCTURES 463

A Through Girder Bridge Encased in Concrete

#1 qmpFoug Isima■wt!rewoktwAin■xfrEle_i_71.1..,./Awka Akin III I all Mo Section On ¢ Of Track Sect ion

Legend Ala Decscripfion 8 Splice plates 32 floor beam bracket 35 Connection I. 37 Waterproofing, 38 Concrete protection 39 Triangle mesh Notei• 48 Ballast for names of parts not 43 Track tie numbered compare "Names 44 Inner guard rail of members in through 4S Tile drain p/ale girder spans.• 46 Trough cover plate 47 Trough web 48 Trough Lis 49 Diaphram

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■■■..– ...r....■... 0 dill.=. ..m, Mitirlildrilliff.raTil...... igiiirithaffizEsogiee—.950einasesamEasEr—:4-saer 4:1 i EillEB lT a lilt II p! 1 41PNITI - --- .,--: NV", Ali V Secfion Section On it Track Legend No Description 8 Splice plates 29 I. beam 32 floor beam bracket 35 Connection L 36 Shelf L 37 Waterproofing 38 Concrete profecio 39 Triangle mesh 40 Reinforcing rod 41 Concrete slab Note:- 42 Ballast for names of part! not 43 Track Tie compare names 44 Inner guard rail of members in through plate 45 Tile drain girder spans.'

Names of Members in Two Designs of Solid Floor Through Girder Spans 464 SUPERSTRUCTURE S

Legend Ala Description. B Splice plates 19 Diaph ram or cross frame E3 Top lateral L IV I 84 Bottom lateral L ru, Side Elevation Concrete 25 Top lateral plate PI sfrainer,-- protection 26 Bottom lateral plate 37 Wafer proofing Triangle mesh... 38 Concrete Protection Waterproofing 39 Triangle mesh 40 Reinforcing rods 2'brain pipe 41 Concrete slab Finish At Drain Pipes 40 Ballast 43 Track tie 44 Inner guard rail 45 Tile drain 50 lateral clip L

Concrete protection Triangle Waterproofing

Note:- For names of detail parts not shown see, "names of members in deck plate girder spans" ÷1".Ben' bolt 6"U.H.-8-0'CtoG .3 /2XJ%4• x 54, Finish At -Abutment Cur'iCrere protection Triangle mesh Waterproofing

Finish Al Curb Angle Names of Members in Solid Floor Deck Plate Girder Span

In plate girder bridges, the floor system is com- The is the earliest type of simple truss, posed of stringers and floorbeams, built up of plates and was patented in the United States by William and angles into an "I" section. That is, a web Howe, in 1840. In this design of truss, the diagonal plate with top and bottom flanges, composed of web members are in compression, the vertical web angles, is carried in turn by two main girders, made up of a solid web plate, top and bottom flanges, consisting of angles, cover plates, and in some cases side plates. TRUSS SPANS A truss is a framework, supported at two or more points, and designed to carry load across the inter- vening space. Such structures are built of wood, metal or a combination of the two materials, and are so designed that little or no stress acts transversely of any member. The earlier stages of American railroading were characterized by a stimulated interest in bridge de- sign, which resulted in the development of various types of bridge truss. A brief description and dia- gram of each of the principal types follows. A Deck Howe

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I!1 Details of a Through Howe Truss Span Railway Engineering and Maintenance Cyclopedia

An Authoritative Manual of Engineering, Maintenance and Signaling Including Definitions, Descriptions, Illustrations and Methods of Use of the Materials, Equipment and Devices Employed in the Construction and Maintenance of Tracks, Bridges, Buildings, Water Service, Signals and Other Fixed Railway Properties and Facilities.

SECOND EDITION-1926

Editor Elmer T. Howson Western Editor of the Railway Age and Editor of Railway Engineering and Maintenance Managing Editor W. F. Rench Formerly Supervisor, Pennsylvania Railroad System Associate Editors Neal D. Howard F. M. Patterson Assisted by Philip George Lang, Jr., (Bridge Section) Engineer of Bridges, Baltimore & Ohio System A. L. Sparks, (Building Section) Architect, Missouri-Kansas-Texas R. R. C. R. Knowles, (Water Service Section) Superintendent of Water Service, Illinois Central System B. T. Anderson, (Signal Section) Superintendent of Signals, Chesapeake & Ohio Ry.

Compiled and Edited in Co-operation with The American Railway Engineering Association and the Signal Section, American Railway Association

A. R. E. A. Committee: C. A. Morse, Chief Engineer, Chicago, Rock Island & Pacific .14. H. R. Safford, Executive Vice-President, International Great Northern—Gulf Coast Lines. C. F. W. Felt, Chief Engineer, Atchison, Topeka & Santa Fe System

Signal Section Committee: F. B. Wiegand, Signal Engineer, New York Central R. R. (West) A. H. Rice, Signal Engineer, Delaware & Hudson Company J. S. Gensheimer, Signal Inspector, Pennsylvania Railroad System

Published and Printed in U. S. A. by SIMMONS-BOARDMAN PUBLISHING CO. 30 CHURCH ST., NEW YORK, N. Y. 608 SOUTH DEARBORN ST., 6007 Euctto AVENUE, MANDEVILLE, LA. CHICAGO, ILL. CLEVELAND, OHIO NEW. ORLEANS 17TH AND H STREETS, N. W., 74 NEW MONTGOMERY ST., 34 VICTORIA ST., WESTMINSTER, WASHINGTON, D. C. SAN FRANCISCO, CAL. S. W. 1, LONDON, ENGLAND METAL GIRDER BRIDGES IN MARYLAND

Metal girder bridges were most likely introduced and first popularized in Maryland by the state's major railroads of the nineteenth century, including the Baltimore and Susquehanna, its successor the Northern Central, and the Baltimore and Ohio Railroad. As discussed, bridge engineering historians have documented the fact that James Milholland (or Mulholland) erected the earliest plate girder span in the United States on the Baltimore and Susquehanna Railroad in 1846 at Bolton Station, near present-day Mount Royal Station. The sides (web) and bottom flange of Milholland's 54-foot-long span were wholly of wrought iron and included a top flange reinforced with a 12x12-inch timber. Plates employed in the bridge were 6 feet deep and 38 inches wide, giving the entire bridge a total weight of some 14 tons. Milholland's pioneering plate girder cost $2,200 (Tyrrell 1911:195). By December 31, 1861, the Northern Central Railroad, which succeeded the Baltimore and Susquehanna, maintained an operating inventory in Maryland of 50 or more bridges described simply as "girder" spans, in addition to a number of Howe trusses. Most of these were probably iron girder bridges; the longest were the 117-foot, double-span bridge over Jones Falls and the 106-foot double-span girder bridge at Pierce's Mill (Gunnarson 1990:179-180).

Perhaps because girder bridge construction technology was not difficult and became readily standardized, few descriptions of nineteenth century deck girder or plate girder construction in Maryland have been located. One such account, however, serves to illustrate how plate girder bridges, initially employed on railroads, became useful to Baltimore City engineers by the 1890s. In 1892, Frederick H. Smith, the prominent Baltimore Bridge Company partner then serving as a consulting engineer to the city, reported that the Campbell & Zell firm had been retained to build a new Lexington-Douglas Street bridge, which was to be "a deck bridge consisting of fourteen plate girders 78 feet long, reaching from wall to wall, and having curved tops upon which are riveted heavy floor plates carrying a granite block roadway 42 feet wide, and two granolithic sidewalks, each 14 feet wide, with heavy steel handrailings along their outer sides and granolithic gutter kerbing along their inner sides." Smith noted with some embarrassment that 13 of the 14 girders were in place, but the "scow with the one remaining girder is stranded in the mud a short distance below the bridge where she has been now for more than a week awaiting the tides" (Baltimore City Commissioner 1892:489).

Girder bridge construction on the Baltimore and Ohio Railroad received a boost between 1901 and 1908, when former Pennsylvania Railroad Chief Engineer Leonor Loree took charge of a major rebuilding of the B&O main and branch lines. Aiming to refit the railroad so that it could safely run 2,500-ton coal trains behind heavy locomotives, Loree ordered construction of a combination deck girder and through truss bridge at the Ilchester tunnel, a seven-span deck plate girder bridge over the Monocacy River, a girder replacement for the old Bollman truss over Tuscarora Creek, and steel plate girder center spans for several trestles along the

110 BRIDGE ENGINEERING

BY HENRY GRATTAN TYRRELL, C. E. Graduate of Toronto University BRIDGE AND STRUCTURAL ENGINEER Author of "Mill Building Construction" (1900) "Concrete Bridges and Culverts" "Mill Buildings" (1910), etc., etc.

PUBLISHED BY - THE AUTHOR CHICAGO, 1911 NEERING. TUBULAR AND PLATE GIRDERS. 195 • over French river, at Rum. important bridges have been npetent engineers, employed )wners, and construction and the plans on a tonnage basis, lroad in the United States, CHAPTER XI. netal bridges, not including an aggregate length of over TUBULAR AND PLATE GIRDER BRIDGES. very three miles of railroad. 262. The first wrought iron girder bridge, which had a idges over the Missouri and span of only 3172 feet, was built by A. Thompson in 1841, elow St. Paul. Not less than to carry a highway over the Pollock and Govan railroad near simple spans exceeding 400 Glasgow, Scotland. It was 2572 feet wide, with six lines of least twenty-five have spans girders. In 1846 William Fairbairn of England erected a pony -ther been demonstrated that tubular girder over the Leeds and Liverpool canal with a le in lengths up to 800 feet span of 60 feet, to carry two tracks of the Blackburn and

s, trusses, girders, trestles, etc . for rail- Bolton railway. In the same year a tubular plate girder bridge ,ondon Engineering, June 8, 19811; Street 1; Canadian Electrical News, May, 1901; was built by James Millholland, on the Baltimore and Ohio mete, Sept. 12. 1902. and Feb. 24, 1905; railroad near Bolton depot, with a span of 50 feet. The sides and bottom of the last bridge were wholly of wrought iron, but the top flange was reinforced with a 12x12 inch timber. The plates used by Mr. Millholland was 38 inches wide and 6 feet -deep, the whole bridge weighing 14 tons and costing $2,200. hese small spans were the first of their kind, and the begin- !Ming of plate girder bridges, which are now so common on merican railroads. 263. Experiments made by Mr. Hodgkinson in 1842, to determine the strength of cast iron and wrought iron beams, disclosed the weakness of the former, and it was proposed that cast iron girders should in the future be trussed with wrought iron bars. The first bridge of this kind was at Tottenham, over the river Lea, the work of G. P. Bidder. The uncertainty in r eference to the strength of those materials caused George Ste phenson, when preparing to bridge the Menai. Straits, to