Summary Paper
Feasibility Study of Standard Sections for Segmental Prestressed Concrete Box Girder Bridges
Felix Kulka Consulting Engineer (At time study was conducted, Mr. Kulka was President of T. Y. Lin International, San Francisco, California)
S. J. Thoman Structural Engineer T. Y Lin International San Francisco, California
egmental prestressed concrete box type, both precast and cast in place, S girder bridges were introduced in were built successfully in the United North America in the late sixties and States and Canada during this time, and early seventies, following their suc- the approximately 70 projects which cessful entry into the European market have been designed to date indicate during the post World War II recon- that the segmental prestressed concrete struction period. Several bridges of this box girder bridge is a very viable alter- native for medium to long span bridge strictures in North America. NOTE: This Summary Paper is a condensation of the results of an investigation commissioned by the Fed- At the same time, it is recognized that eral Highway Administration on the feasibility of using the design and construction of seg- standard sections for segmental prestressed concrete mental bridges still largely follow prac- box girder bridges. The study was initiated in 1980 and completed in July of 1982. The full length report, tices in Europe and that a closer iden- entitled - Feasibility of Standard Sections for Seg- tification with American construction mental Prestressed Concrete Box Girder Bridges" practice is in order. Standardization of {FHWA RO-82;024) by F. Kulka, S. J. Thoman, and T. Y. Lin is available from the National Technical In- certain aspects of segmental box girder formation Service, Springfield, Virginia 22161. bridges appears to he one way to ex-
54 Synopsis Presents the highlights of a study which investigated the feasibility of developing standard sections for segmental prestressed concrete box girder bridges. The report is based on an extensive survey of segmental box girder bridges in the United States and Canada. Recommendations are given for specific items that could be standardized, while also discussing areas which might not be appropriate to standardization.
pand their economical use by instilling specific areas which should be standar- confidence among bridge engineers dized are listed and discussed in the and by producing a cost effectiveness report, as are those which are not cur- through uniformity in design, thus rently subject to standardization and permitting precasters and contractors to those which are questionable. invest in forms and equipment on a broader basis than is done today. Scope of Study This report deals with the feasibility of standardizing segmental prestressed Standardization of highway construc- concrete box girder bridges in the tion elements is a long-standing prac- United States. The study relied heavily tice in the American highway industry. on a survey of bridge engineers in the Development of the AASHTO-PCI I- United States and Canada, which pro- girders is one example; precast con- duced valuable information on all crete culverts, traffic barriers, and piles bridges of this type. Statistical studies are other examples. It is fairly well were conducted to determine correla- agreed that standardization has merits tions and uniformity of significant pa- in cost savings, reduction of construc- rameters, particularly with respect to tion time, and improved product qual- geometry. ity. Analytical design studies, mainly to It was felt that for standardization of determine the economical use of mate- box girder sections to succeed, a uni- rials, were made to augment the statis- form approach should be used in order tical analyses. The results were to permit bridge engineers to design evaluated both qualitatively and quan- such sections with a sufficient degree of titatively, and an advisory technical re- uniformity and to allow precasters and view committee was formed to review contractors to bid and build them as the content of the study and its recom- they would any other advanced type of mendations. structure. The report takes the position that The object of this study, then, was to standardization of segmental pre- consider all the advantages and disad- stressed concrete box girder bridges is vantages of standardization and make possible and should be initiated. The appropriate recommendations for future
PCI JOURNAUSeptember-October 1983 55 development. In doing so, care was State of the Art of taken not to let standardization limit Box Girder Bridges competition, rather, standardization was approached with a view towards Cast-in-place, conventionally formed exploiting all the alternatives, thereby box girder bridges had been used in improving design and increasing com- North America for many years when, in petition. The scope of the study in- the late sixties, segmental box girder cluded: construction was introduced to the 1. An assessment of the state of the continent. This type of structure was a art of segmental bridge construc- European development of the post- tion. World War II era, when the reconstruc- 2. Development of design constraints tion of war-torn European countries as affected by construction limita- demanded methods of construction tion s. which would overcome the scarcity of 3. An analysis of costs and benefits of labor and which would produce many standard sections. structures in the shortest possible time. 4. Development of specific recom- The development of cast-in-place seg- mendations concerning the feasi- mental construction is generally attri- bility of standard sections for seg- buted to Germany, while precast seg- mental prestressed concrete box mental construction is primarily a girder bridges. French innovation. Since the volume of construction was large and there was sufficient invest- Study Approach ment available, the box girder became It was felt essential that the recom- popular even though it is not necessar- mendations concerning possible stan- ily the most economical section for all dardization be based on experiences conditions. The box girder can, how- with existing practices rather than on ever, safely accommodate spans up to arbitrary judgments. 800 ft (244 in) and resist a wide range of Accordingly, a questionnaire con- stresses. Furthermore, its resistance to cerning prestressed concrete segmental torsion made the box girder particularly box girder bridges was sent to bridge suitable for cantilever construction, engineers in all states and territories which proved to be a good method for plus the provinces of Canada. The sur- rapid construction and for achieving vey included bridge site, state of com- long spans without the use of falsework pletion, cross section, design and de- or shoring. tails, construction, costs and other per- The Lievre River Bridge in Quebec tinent information. The response was (completed in 1967) was the first pre- excellent, and the information collected cast prestressed segmental bridge built provided a good sampling for further in North America. This was followed in-depth studies. shortly by the Bear River Bridge near The data obtained were categorized Digby, Nova Scotia. The first major and statistical studies were made to segmental box girder bridge in the evaluate significant parameters, leading United States was the JFK Memorial to a rational assessment of the state of Causeway in Corpus Christi, Texas the art of segmental bridge design and (completed in 1973). construction. Analytical studies were As a result of a fairly active program performed in cases where data were not of promotion, more than 50 segmental available, permitting the establishment bridges have been constructed in North of qualitative and quantitative relation- America since that time. Their record ships. with respect to economy and successful
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