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TRANSPORTATION |
Number E-C007, March 1999 ISSN 0097-8515 |
FIFTY YEARS OF TRB BRIDGE COMMITTEES By and C. P. Siess
I. M. Viest
IMV Consulting
P.O. Box 132
Hellertown, PA 18055
telephone: (610) 865-1041
fax: (610) 865-1041
University of Illinois
401 Burwash Avenue, No. 132
Savoy, IL 61874
telephone: (217) 352-0989
fax: (217) 351-1728
e-mail:
TABLE OF CONTENTS
FIFTY YEARS OF TRB BRIDGE COMMITTEES
The paper "Fifty Years of TRB Bridge Committees," by I.M. Viest and C.P. Siess, traces the history and accomplishments of committees in the bridge and structures area of TRB since the first committee was formed in 1949. The paper was submitted for the 1999 TRB Annual Meeting, underwent a full TRB peer review, was presented by Viest in Session 403 of the Annual Meeting, and was recommended for publication. Since the paper was not of a "typical" nature suitable for a TR Record, it was decided that it be published electronically within the TRB web site. Our thanks go to the authors for documenting this aspect of the history of the Transportation Research Board.
FOREWORD
ABSTRACT
INTRODUCTION
ORGANIZATION
ACCOMPLISHMENTS
Publications
Bridge Research
TRB Bridge Engineering Conferences
TRB Bridge Management Workshops
ACKNOWLEDGMENTS
REFERENCES
The first Bridge Committee in the Highway Research Board (HRB) was organized in 1949 in the Department of Highway Design. Today, 11 committees in the Transportation Research Board (TRB) deal specifically with the design, construction and maintenance of bridges and related structures. Historical development of the organization of bridge committees is described first. Discussion of their accomplishments follows, under the headings of annual meetings, publications, research, conferences and management workshops. It is concluded that TRB bridge committees serve today as the principal catalyst for bridge research in the United States.
The Transportation Research Board organization includes 11 committees dealing with the design, construction and maintenance of bridges and related structures. The Structures Section, primarily interested in design, has seven committees and one task force. There are two committees concerned with bridges in the Construction Section, and one each in the Soil Mechanics and Maintenance Sections. A historical listing of the TRB bridge and related committees is presented in Table 1.
Starting with one committee of six members, the membership of the bridge and related committees has grown over the past 50 years to about 250. Overall, more than 800 individuals have served through 1998. A listing of 770 committee members that contains information on years of service and assignments is available on request.
On October 31, 1949, Glenn S. Paxson, Bridge Engineer of the Oregon State Highway Commission, wrote the following in a letter to Professor Chester P. Siess of the University of Illinois:
The Highway Research Board is organizing a Committee on Bridges in the Highway Design Department. I have been appointed as chairman of this committee. One member of this committee should represent the viewpoint of the Universities, and I would like to have you serving in this capacity. I believe the committee can do a very worthwhile work in encouraging research along highway bridge lines and in providing opportunity for the publication and dissemination of the resulting information.
For several years prior to 1949, Professor Siess and other interested individuals had attended the annual meetings of the Bridge Committee of the American Association of State Highway Officials (AASHO), also attended by the Bridge Engineer from every state. The purpose of these meetings was to develop an annual update of the AASHO Bridge Specifications, published in a book form at four-year intervals. Changes adopted between the publication years were issued as annual interims. The "interested individuals" came mainly from academia, federal government and industry. They provided the committee with factual information, often resulting from their own research. The feeling developed among these outsiders that it was desirable to establish a forum concerned with research on highway bridges, which would be open to all interested individuals. The Highway Research Board was the logical home for such a forum. The Committee on Bridges was established in the Department of Highway Design.
The new committee had five members, in addition to chairman Paxson:
The Committee on Bridges held its first meeting on May 2 and 3, 1950, in Washington, D.C. Present were members Archibald, Erickson, Paxson and Siess, three other interested engineers (F. Burggraf, C. N. Conner and G. S. Vincent) and Wray. The following four items were approved as the objectives of the committee:
The Committee developed plans for a session on the subject of highway structures for the January 1951 HRB annual meeting. The session included papers on experiments with heating bridge decks and pavements,1 design and construction of precast concrete bridges,2 high-strength bolts for steel structures,3 a theory describing the behavior of a certain kind of underground conduit4 and the first report of the new committee.5 The next committee meeting was scheduled for the annual HRB meeting, which became the standard practice.
The first subdivision of the Bridge Committee is listed in the 1959 HRB Directory as the Subcommittee on Study of Friction Pile-Bearing Capacity (Table 1). It was chaired by Archibald. Five additional subcommittees were organized in 1962, after John N. Clary, Bridge Engineer of the Virginia Department of Highways, became the second chair of the Committee on Bridges. In the 1964 reorganization of HRB committees, the six subcommittees were transformed into six committees grouped as the Bridge Division. The committees of the division were named and chaired as follows:
In 1969, the last two committees were combined and named the Committee on Dynamics and Field Testing of Bridges, reducing to five the number of committees in the Bridge Division. Designated as Section C - Bridges, the division was enlarged in 1970 by the transfer of the Committee on Culverts and Hydraulic Structures, and again in 1988 and 1996 by the creation of task forces on fiber- reinforced plastics and seismic design. The name of the section was changed in 1973 to its current designation, Section C – Structures, and that of the Board, to TRB. The original Committee on Bridges, its subcommittees and all constituent committees of Section C, as well as the names and years of service of committee chairs, are listed in Table 1. The names and years of service of Structures Section chairs and staff representatives are given in Table 2. It includes data for the original Committee on Bridges.
The current (1998) Section C committees and chairs are
Table 1 also includes bridge-related committees concerned with construction and maintenance. In 1962, Kenneth R. Scurr, Bridge Engineer of the South Dakota Department of Highways, organized the Committee on Construction Practices - Structures as a unit of the Construction Section of the HRB Department of Materials and Construction. In 1970, the name was changed to Construction of Bridges and Structures. Its current chair is Ralph D. Csogi, a consulting engineer from upstate New York. The first bridge committee in the Department of Maintenance was formed in 1950 under Structures Maintenance and Management. It is chaired today by Wallace T. McKeel, Jr., Research Manager of the Virginia DOT.
Of the over 800 individuals that have served on the bridge and related committees, more than 600 were members of one committee only. Service on two committees was frequent (over 100), about 50 served on three, and at least nine individuals served on four to six different committees. The average total length of committee service per individual was seven years. Five persons served for more than 25 years, the longest service to date being 33 years. Seventy-nine members chaired one or two committees, for an average tenure of four years.
There were several other HRB and TRB committees, not included in this study, whose work involved some bridge-related topics. Perhaps the foremost among them was the Committee on Metals and Welding, in the General Materials Division. Chaired by LaMotte Grover of the Air Reduction Sales Company, it predated the first HRB Bridge Committee by two years. It included several state and federal bridge engineers, and engineers from the industry. The last listing of the Committee on Metals and Welding dates from 1961. It was replaced by the Committee on Metals in Highway Structures, established in the General Materials group in 1962.
It will be of interest to note at this point that the formation of a bridge committee had already been proposed in the first report on the organization of the original Advisory Board on Highway Research. Prepared by the Committee on Research and Research Committees, chaired by Testing Engineer of the Iowa State Highway Commission Thomas R. Agg, the report listed "Committee on Highway Bridges" as Item V. "To establish all of the data required for the design of highway bridges" was its proposed task. The report stated further that "The following will indicate the type of research required:"
The report was discussed at the meeting of the Board held in New York City on January 16, 1922, but the Minutes include no discussion or action on Item V.
The most important accomplishment of the HRB Committee on Bridges was the creation of an annual meeting place for the entire highway bridge engineering community, and a forum for presenting and debating the latest developments in the field. Other achievements to date include
The bridge and related committees have met regularly at the annual TRB meetings, bringing together state, federal and local officials, researchers, designers, consultants and industry representatives. They have organized and conducted sessions on various bridge topics as a part of the general program of the TRB annual meetings. From time to time, they have identified problems requiring solution, mainly by developing research-needs statements in their particular areas of interest, and assigning priorities to individual projects. The members of the committees were called on to review papers on bridge topics submitted to the Board. During the last decade or so, the committees scheduled presentations of short papers within the scope of their individual interests, as a part of their committee meetings.
A few presentations concerned with some aspects of highway bridges were made at the HRB annual meetings even before the formation of the Bridge Committee. Possibly the first was the general report of the Committee on Maintenance,6 which included a short section titled "Bridge Maintenance,"7 prepared by J. T. Donaghey. The following items were discussed: regular maintenance of bridges, proper painting and re-flooring, foundation maintenance, and design of bridges with reference to subsequent maintenance. A discussion of Donaghey's section by Owens8 emphasized the need for systematic inspection by competent inspectors, and discussed the likelihood of restoring early concrete bridges made with poor-quality concrete, as well as a few other items. The 1930s brought papers on the effect of bridges on the load limits on highways,9 high-elastic-limit steel as reinforcement for concrete,10 bridge traffic patterns11 and stability of bridge piers.12 They were followed by 17 papers during the 1940s, with topics ranging from bridge foundations13 and field tests14 to descriptions of specific bridges and bridge types.15 During the 1950s, that is, after the formation of the Committee on Bridges, the number of bridge papers presented at the annual HRB meetings jumped to 78, averaging about eight per year. The increases in the number of papers continued through the following decades. The average number of bridge papers presented thus far during the 1990s has exceeded 55 per year.
In the 1960s and 1970s, there were about six sessions per year on bridges at the HRB and TRB annual meetings. This increased to nine sessions per year in the 1980s, and 14 sessions during the 1990s. Roughly 1,200 bridge papers were presented at the numbered sessions of the TRB annual meetings since 1960. An emphasis on prestressed concrete in the 1950s was replaced with a great variety of topics covering all types of short- and medium-span highway bridges, including concrete, steel and timber construction. Innovations dealt with were, among others, weathering steel, high- strength concrete, load and resistance factor design, box girders, segmental construction and curved girders. Examination of failures was always a prominent feature of bridge sessions. During the past two decades, history and aesthetics appeared occasionally on the program. More recently, bridge management and the three Rs - repair, rehabilitation and retrofit - became the buzzwords. Seismic design, fiber-reinforced plastics and high-performance steels are counted among the most recent entries. Among the session format innovations, panel discussions have proved popular.
The following topics of presentations made at the annual meetings are intended to illustrate the scope and breadth of the areas covered. They are listed in chronological order.
Recent Developments in Precasting of Highway Bridges
Effects of Trucks on Bridge Floors in Iowa in 1922 and 1948
Composite Construction for I-Beam Bridges
Research on Highway Bridge Floors
Comparative Costs of Prestressed and Conventional Bridges
Prestressed-Concrete Bridge Costs
Prestressed Concrete in California
Endurance of a Full-Scale Pretensioned Concrete Beam
Insulated Forms for Winter Construction of Bridges
Corrosion-Resistant Low-Alloy Steel in Highway Bridges
Dynamic Behavior of Simple-Span Highway Bridges
Rehabilitation of Deteriorated Bridge Slabs
Prediction of Permanent Camber of Bridges
Bridge Expansion Joint Sealants
Fatigue Behavior of Welded Beams
Investigation of Prestressed Concrete for Highway Bridges
Steel Box-Girder Bridge Failures
Rio Niteroi Bridge Construction
Evaluation of Existing Bridges
Historic Bridges
Creativity in Bridge Aesthetics
Rehabilitation of the Arlington Memorial Bridge
Selection of Limit-State Values: Segmental Concrete Bridges
Ship and Barge Collisions with Bridges
Seismic Retrofitting of Bridges
Strengthening Highway Bridges with Carbon Fiber Materials
Laboratory Studies on Bridge-Scour Countermeasures
Bridge Construction with High-Performance Steel
Since its establishment, HRB has published information related to highway research. The first periodic publication, the HRB Proceedings, was published annually from 1921 to 1962. Over the years, a number of more narrowly focused periodicals were added. By 1963, the Proceedings were replaced by the Highway Research Record, issued at irregular intervals, and by the quarterly Highway Research News, both of which have been continued to the present. The early bridge papers were published in the Proceedings. In recent years, most of them appeared in separate issues of the Transportation Research Record, the individual issues usually containing only papers on bridges and other highway structures.
Even without papers presented at the TRB bridge engineering conferences and published in separate conference proceedings, the output of bridge papers continued to increase throughout the years. Twice as many were published in the 1960s as in the 1950s, and the output doubled again during the 1980-89 decade. Including those in bridge conference proceedings, the total number of bridge papers published by TRB through 1997 is estimated well above 1,500. The number that will be published during the 1990s is certain to exceed 500. Today, TRB is the principal organization for the dissemination of the results of bridge research in the United States.
The Board honored six papers on bridge topics published in the Transportation Research Record. Four of the winning papers received the K. B. Woods Award,16,17,18,19 and one each the 1975 TRB Award20 and the D. Grant Mickle Award.21
During lunch in the dining room of the former Roger Smith Hotel in Washington, D.C., HRB Bridge Committee members Erickson, Paxson and Siess discussed whether the proposed AASHO Road Test, originally planned as a study of highway pavements only, could also be utilized for research on bridges. Since it was obvious that a statistically designed multivariable program was out of the question for bridges, it was decided that a few tests to determine how various bridge types behaved under repeated overloads would be both feasible and worthwhile. As a result, the suggestion for such tests was made to the AASHO Bridge Committee, chaired by Archibald, and that committee in turn requested that bridges be included. The recommendation resulted in the inclusion of 18 bridges of various types in the program.22 The Advisory Panel on Bridges at the Road Test, chaired by Paxson, enlarged the scope of the project by adding studies of impact suggested by Siess and, toward the end of the testing phase, tests on failure with increasing overloads, as suggested by the Road Test staff. Bridges that survived the principal series of a large number of repeated loads, conducted with one type and weight of vehicles on any one bridge, were subjected to a few repeated passages of higher and higher overloads until failure occurred.
The tests resulted in fatigue failures in all three types of beams included in the project: structural steel, reinforced concrete and prestressed concrete. However, they affected primarily the design of steel bridges. In 1965, the old provisions for alternating loads in the AASHO Specifications23 were replaced and expanded with new requirements for fatigue stresses.24 Several projects25,26,27 of the National Cooperative Highway Research Program (NCHRP) followed in order to obtain more detailed information for fatigue design and repair. The results, combined with a simplified design procedure suggested by the studies at the AASHO Road Test,28 led to another basic revision of the requirements for fatigue.29,30 The impact studies lead to the conclusion that it is entirely possible to obtain highly reliable experimental data from field tests of bridges.22,31 Another aspect of bridge design and evaluation for which the AASHO Road Test provided reliable and, perhaps, unique information is that of bridge overloads.22
The research pointed the way toward a fundamental improvement in the design of highway bridges: the replacement of the historic approach, based on working stresses, with a design based on the maximum strength of the individual bridge elements. The first step was the so-called Load Factor Design,32 developed for steel bridges as a project sponsored by the American Iron and Steel Institute, and later extended to reinforced concrete bridges. Load Factor Design, adopted by AASHO in 1971,33 required separate evaluation of the strength of the elements, and of the overall performance of the bridge under the effects of everyday traffic. The next step involved adding a probabilistic approach: the load and resistance factors that define the safety of a bridge were derived with the aid of the theory of probability. The resulting Load and Resistance Factor Design34 was the end product of a multiyear project conducted by the consulting firm Modjeski and Masters for the NCHRP. Many experts from state and federal highway departments, academia, consulting design offices and industry participated in this work. The AASHTO document34 contains the best available information concerning the design of highway bridges, based on fundamental knowledge accumulated from many research studies carried out over the decades after the AASHO Road Test.
Although the bridge research at the AASHO Road Test was the largest research project with their involvement, the TRB bridge committees participated in numerous other bridge research efforts. Already mentioned was the study of friction pile-bearing capacity early in the life of the first Bridge Committee. Another early example was the wind-tunnel investigation of bridge models, carried out at the Bureau of Public Roads laboratory at Langley, Virginia. The HRB Board administered the project at the request of AASHO. Since the Road Test, the NCHRP led to a direct participation by many Bridge Committee members in numerous bridge projects, such as Distribution of Wheel Loads on Highway Bridges,35 Effects of Weldments on Fatigue Strength of Steel Beams,25 Cathodic Protection of Reinforced Concrete Bridge Decks,36 Bridge Management Systems,37 Inelastic Rating Procedures for Steel Beam and Girder Bridges,38 and Development of Comprehensive Bridge Specification and Commentary. To date, the NCHRP included 80 bridge projects, of which six are in progress and six are pending. The findings were made available to the public in 41 NCHRP Reports and numerous other publications. Furthermore, a continuing involvement of the bridge committees in research was accomplished by committee deliberations, by compiling research-needs statements and by selecting papers for presentation at the annual meetings.
TRB Bridge Engineering Conferences
Starting in the late 1950s, the HRB began organizing special conferences focusing on some topic of timely interest.39 Although a few were held in conjunction with the annual meetings, most were staged separately at various locations around the country, usually during the middle months of the year. For example, the so-called HRB Western Summer Meeting convened in August 1970 in Sacramento to discuss the topic of "Improving Pavement and Bridge Performance." In line with these new activities, Lawrence F. Spaine of the TRB staff proposed in the early 1970s to organize from time to time a bridge engineering conference. He was well-aware that the small number of bridge sessions at the annual meetings covered only a fraction of the bridge research topics and, even more important, that only a few bridge engineers were able to attend the annual meetings. The first such conference was held in September 1978 in St. Louis. It was well-attended and well-received. Other conferences followed in 1984, 1991 and 1995. The fifth conference is scheduled for the year 2000, in Tampa, Florida, April 3-5.
The Transportation Research Board sponsored all four conferences. Sixteen other interested organizations joined the TRB, either as cosponsors or as cooperating agencies (Table 3). The Federal Highway Administration cosponsored all four conferences. The principal statistics of the four conferences are summarized in Table 4. Each conference was held at a different location, thus providing an opportunity to a new group of engineers to participate, without the need for long travel. Except for the fourth conference, about one-half of the attendees were employees of state, federal and local governments, the rest coming from consulting offices, industry and academia. At the fourth conference, the proportion of the academic contingent was considerably higher, primarily because of large foreign attendance. Geographically, the four states with the largest participation are listed in the decreasing order of the number of attendees. In every case, the number of states given as residence was around 40. Excluding Canada, the number of attendees from abroad was less than 5 percent at the first three conferences, and over 30 percent at the fourth conference. The fourth was labeled as international, and held immediately after and at the same location as the annual meeting of the International Association for Bridge and Structural Engineering.
Technical reports prepared in the form of written papers were published by the TRB either in the Transportation Research Record or Conference Proceedings series. The opening session at each conference included several addresses of general nature. They were recorded in TRB Circular No. 20140 for the first conference, but no record is available for the other three conferences. Each conference had a steering committee that provided overall guidance and advice to the TRB staff charged with organizing the meeting. Overall, 65 persons served on these committees. They are listed in Table 5.
The TRB Bridge Engineering Conference at St. Louis41 was organized to facilitate an interchange of information on all aspects of design, construction, rehabilitation and maintenance of vehicular bridges, and to have specific emphasis on problems and solutions of interest to highway, railroad and transit bridge engineers, administrators and managers. The topics covered were inspection, rehabilitation and replacement of bridges in service (13 papers), fatigue behavior of bridge elements (10), problems related to bridge deck slabs (five), loading, safety and posting (nine), miscellaneous design topics (14), model studies and field tests (seven) and construction (eight). The following are a few examples of specific papers: "Extending the Service Life of Existing Bridges," "Repair of Poplar Street Complex Bridges in East St. Louis," "Dynamic Response of Bridges," "A Demonstration Project for Deicing of Bridge Decks," "Correlating Bridge Design Practice with Overload Permit Policy" and "Concrete Cable-Stayed Bridges".
The Second Bridge Engineering Conference at Minneapolis42 had the same general purpose as that at St. Louis, but its main concern was with short- and medium-span structures. It included five sessions on structural design practices, with papers ranging from "Feasibility of Computer-Aided Drafting" to "Design of the Cable-Stayed Mississippi River Bridge at Quincy, Illinois." Three sessions dealt with service considerations such as "Renovation of the Third Avenue Bridge in Minneapolis" and "Rehabilitation of Steel Deck Girder Bridges." The paper "Construction of Posttensioned Bridges in Germany" was a part of the session on construction, and "Postconstruction Evaluation of the Fremont Bridge" was presented in the session on testing and evaluation. Finally, the "Case History of Scour Problems of Bridges" was one of 15 talks given in three sessions on bridge hydraulics, which also included a panel discussion.
The Third Bridge Engineering Conference at Denver43 covered research and practice resulting from bridge studies performed under the NCHRP, sponsored by AASHTO, as well as under various federal, state and other research agency programs. "Modeling Live Load and Dynamic Load for Bridges," "Corrosion and Its Influence on Strength of Steel Bridge Members," "Expert System for Determining the Disposition of Older Bridges" and "Design of Laminated Elastomeric Bridge Bearings" are examples of such studies reported at the Conference. A session on segmental and cable-stayed bridges included, among others, the paper "Construction and Design of the Dame Point Bridge." The paper "Recent Advances in Seismic Design and Retrofit of Bridges" was one of seven presented on questions of earthquake effects. One session dealt with bridge management.
The Fourth International Bridge Engineering Conference at San Francisco44 provided an international forum for exchange of bridge research results and technical information on planning, design, construction, maintenance, repair, rehabilitation and replacement of bridges. Sixteen technical sessions dealt with management systems, design, performance and rehabilitation, materials and detailing, aesthetics, construction and long-span bridges. The participation from foreign countries included papers from Australia, Hungary, Italy, Japan, Poland, Spain and the United Kingdom. A few of the titles were "Bridge Architecture: The Good, the Bad and the Ugly," "British Practice in Arch Bridge Assessment," "High-Performance Concrete for a Floating Bridge," "Advanced Composites for Bridge Infrastructure Renewal," "Effectiveness of Hinge Restrainers as Seismic Retrofit Measure," "Bridge Bearing Replacement," "External Prestressing for Bridge Rehabilitation in Italy," "Bridge Pier Analysis for Ship Impact" and "LRFD Code for Wood Bridges."
TRB Bridge Management Workshops
In 1987, TRB held a workshop on bridge management. The reason for the workshop was partly the expressed needs of state bridge engineers and partly the preliminary findings in NCHRP Project 12-28(2) Bridge Management Systems.37 The introduction to the first interim project report in 1986 stated: "The need for an overall management concept for bridges becomes increasingly apparent. Acceptable experience and equations exist to design and construct adequate bridges, but as existing bridges weather and wear out, what rules or models govern their behavior? In the face of limited funds and knowledge of life-cycle performance, what is the best way to ensure optimum investment for the many bridges in need of maintenance, rehabilitation, or replacement?"
The workshop convened in Washington, D.C., on January 11, just before the regular TRB annual meeting. Similar workshops were held in Washington during the following five years. Group 2 and 3 Councils sponsored the first five. Group 3 Council alone sponsored the sixth. In 1993, the meeting was 22 days long, and its name changed from workshop to conference. The time and place were September 15 to 17, in Austin, Texas. TRB Committee A3C06 on Bridge Maintenance and Management sponsored the conference, in cooperation with the Texas Department of Transportation and the FHWA. The personnel involved in organizing the seven meetings are listed in Table 6. Each meeting started with opening remarks usually in a keynote address, and ended with concluding remarks, generally by the chairman of the organizing committee. The average attendance at the workshops was about 90, with a large portion of the attendees connected with state highway departments. Planning is in progress for the eighth TRB meeting on bridge management. It will convene in April 1999 at Denver.
The seven workshops held to date included well over 60 papers and panel discussions related to the general theme of bridge management. The papers fit into the following categories: issues, experiences, theories, needs, guidelines and support. The first workshop was concerned primarily with issues and experiences. To these two subjects the second workshop added modeling for future needs. The third included experiences abroad and in other fields. How to obtain and correlate information required as input into the bridge management systems was the next workshop topic. The main concerns of the 1991 meeting were various aspects of bridge deterioration. Most of the papers in that year dealt with correlation by models and theories, including the FHWA advanced theoretical framework Pontis. The sixth workshop contained reports by several states on their implementation, a discussion of AASHTO guidelines and a report on the NCHRP project. An emphasis on activities conducted in support of the bridge management systems was the new program feature in 1993.
It is clear from this brief review that the results over the past 50 years testify to the wisdom of those who established the original Bridge Committee in the Highway Research Board. Ample proof is on hand:
Furthermore, the TRB national bridge engineering conferences became a forum for more focused coverage of ongoing research and other innovative activities, and the newer workshops dealt with questions of bridge management.
However, it is also fitting to point out that some of the activities were not as effective as they could have been, and that work in other desirable areas was not pursued. An example of marginally effective activities is the periodic development of a list of research needs and assignment of priorities, as suggested by R. C. Cassano. Many worthwhile research areas were identified in this process, but very little came of most of them. If this activity is to be continued with improved prospects for effectiveness, it is necessary to establish a mechanism for further refinement of the process and a means of identifying early funding sources for a significant number of the proposed projects.
An opportunity exists in TRB to encourage greater interaction between the various bridge- related committees. R. C. Cassano, while chairing the Structures Section, convened a meeting of the chairs of all bridge-related committees in the TRB. Cassano's successors, D. B. Beal and A. S. Nowak, held similar meetings. Such meetings encourage fruitful interaction that may well result in synergistic effects.
The authors wish to express their gratitude to R. C. Cassano, D. W. Dearasaugh, Jackson Durkee, J. M. Hanson, F. D. Hejl, R. A. Imbsen, F. N. Lisle, A. S. Nowak, B. L. Post and R. A. P. Sweeney. They contributed in the form of historical materials, suggestions and comments, as well as by their encouragement of the preparation of this paper.