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Public Roads - Summer 1995

Bridge Research: Leading the Way to the Future

The collapse of the Silver Bridge -- connecting Gallipolis, Ohio, and Point Pleasant, W.Va. -- in December 1967 was precipitated by the stress corrosion failure of an eyebar link. As a result of this collapse, a national bridge inspection and replacement program was initiated, and research of nondestructive evaluation technology applied to bridges was stimulated.



The nation spends at least $5 billion per year for highway bridge design, construction, replacement, and rehabilitation. Although the amount of new construction and the number of deficient bridges have declined, the amount of expenditures continues to rise. This article discusses the role and value of research as part of the nation's investment in highway bridges.


The continued economic strength and growth of the United States is intimately linked to the strength and reliability of our highways and bridges. The American public is experiencing the effects of an aging and deteriorating highway system. Increased delay, discomfort, and congestion, along with reductions in safety and service, are frequent. Highway agencies are struggling to cope with the increasing demands on their highways, and deteriorating bridges are becoming more severe choke points in the system.


The Mianus River Bridge collapse in Greenwich, Conn., June 1983, resulted from a hangar pin connection failure due to excessive corrosion accumulation. This failure again emphasized that specialized bridge inspection equipment and maintenance is needed.


There is an argument that the government should play a more vigorous role in promoting new technology. Clearly, standing still technologically is, in fact, an invitation to lose the technological and competitive edge. There are many forces at work that can erode the productivity gained by past advances in technology.

Transportation is an overhead cost (about 20 percent) of all goods and services in this country. Any reduction in that overhead is a general gain, freeing resources to produce other goods and services or allowing better distribution of those goods and services for the same cost. Research is an essential part of this reduction.

Unfortunately, research is often reactive, conducted in response to emergencies. In December 1967, a "new" technical issue emerged tragically with the loss of 46 lives in the collapse of the Silver Bridge between Point Pleasant, W.Va., and Gallipolis, Ohio. Even though structures such as the Silver Bridge have been the subject of investigation for some time, the issues of fatigue, fracture, and fracture-critical members suddenly demanded an accelerated search for answers.

A few more names from the recent past -- Mianus River Bridge, Hatchie River Bridge, Schoharie Creek Bridge, and the San Francisco-Oakland Bay Bridge -- bring to mind a chain of events: a spectacular and tragic collapse, extensive media coverage, congressional inquiry and detailed investigation, and calls to make the technical issue involved a top priority in research and implementation.


The Hatchie River Bridge failure (Top) in Covington, Tenn., in April 1989 and the Schoharie Creek Bridge collapse in New York in April 1987 pointed to the need to better understand and design for scour effects on bridge piers and abutments. These failures caused the acceleration of research in scour.


In many of these cases, the problems were foreseen, and warnings were sounded by one or more alert structural engineers. However, potential solutions were delayed by either the excessive costs imposed by existing technology or the reluctance to adopt new technology. In some of these cases, improved inspection technology would have allowed the problems to be spotted in time.

As a minimum, our goal is to break that chain of failures by conducting a proactive research program that provides solutions that can be implemented prior to the catastrophic failure.

The key to improving highways in the 21st century will be the use of advanced or enhanced materials, inspection technology, design procedures, construction methods, operational practices, maintenance and rehabilitation technology, and management techniques. We must use technology that permits rapid repair and return to service with minimal disruptions to safety and traffic flow. The challenge to develop and implement this technology must be undertaken in partnership with the entire highway community -- government at all levels, universities, highway users, the construction industry, and heavy vehicle manufacturers. The highway community must shift gears in the highway program to anticipate and meet system shortcomings before they further impair service.

Thus, we need to give research and implementation a higher priority; to back that priority up with dollars; and to anticipate emerging issues and problems. Today's actions are not sufficient to address current problems and needs. But do we know or accept the value of research? Is the value of research quantifiable? Perhaps one can gain insight by examining the status of the nation's bridges, estimating the research investment for bridges, quantifying some specific cases or values of bridge research, and then drawing some conclusions.

Status of the Nation's Bridges

The 1993 report of the secretary of transportation to the U.S. Congress on the status of the nation's bridges concludes that, although bridge conditions are improving slightly, approximately 35 percent of the bridges in the United States are classified as deficient -- either structurally deficient (21 percent) or functionally obsolete (14 percent).(1-2) This compares to 37 percent, 21 percent, and 16 percent, respectively, in the 1991 report.

Structural deficiency does not necessarily imply that a bridge is unsafe. It does, however, mean that a structure is unable to carry the vehicle loads or tolerate the speeds that would normally be expected for that particular bridge in its designated system. Functional obsolescence means that the bridge has inadequate width or vertical clearance for its associated highway system. In some cases, bridges become functionally obsolete because of highway improvements on the approaches to the bridge, such as lane additions or widening of approaching roads. In other cases, a bridge may be classified as functionally obsolete through a redefinition of desired standards.

As shown in table 1, the cost of repairing all backlogged bridge deficiencies that existed June 30, 1992, is approximately $78 billion. This could increase to as high as $131 billion if improvements are delayed. The cost to maintain current overall bridge conditions is estimated at $5.2 billion annually. Approximately $8.2 billion annually is required to eliminate all backlogged and accruing bridge deficiencies through 2011. (This translates to rehabilitating or replacing about 12,000 bridges each year -- about 250 per state.) Yet, current total bridge expenditure, including new construction, is estimated to be approximately $5 billion per year from all sources -- federal, state, and local -- leaving a significant shortfall if the nation is to eliminate the deficiencies in its inventory of aging bridges.

What Value Is Research?

What is the current investment in bridge-related research, and of what value is research to address the technical problems associated with reducing deficiencies in today's bridges and improving the performance of tomorrow's bridges?

Both questions are difficult to quantify for various reasons. First, many organizations support and conduct bridge-related research, making it difficult to estimate annual expenditure. Second, bridge research expenditures are usually lumped into highway-related research budgets, as was the recent $30 million annual expenditures for the now-completed Strategic Highway Research Program (SHRP). Benefits and the applicability of research to bridges vs. pavements from SHRP can be, at best, estimated. The same can be said for programs sponsored by other agencies, such as the Department of Defense, which makes a substantial contribution to address bridge-related problems. Finally, while specific examples can be cited that quantify the value of research, drawing a general conclusion can be misleading.


Collapse of a connector span of the San Francisco-Oakland Bay Bridge Oct. 17, 1989, stimulated research on the vulnerability of the nation's highway bridge to earthquakes.


The main research partners who provide financial support for bridge-related research include the Federal Highway Administration (FHWA), the National Cooperative Highway Research Program (NCHRP), the State Planning and Research Program (SP&R), and the National Science Foundation (NSF). Although no hard figures are available, I estimate that the 1991 bridge research investment from the traditional sponsors listed above is between $25 million and $30 million; approximately one-third of that estimated total is being provided through the direct research programs of FHWA and NCHRP. This estimate does not include Department of Defense agencies and other organizations, such as the National Institute of Standards and Technology (NIST), and the private sector, who play a critical role in the sponsorship and conduct of important bridge research.

"Beauty is in the eye of the beholder!" The value or importance of research is difficult, if not impossible, to quantify. Specific examples, however, can be cited. For example, 5-to-1 and 10-to-1 productivity gains have been attributed to research and development of computer-aided bridge design tools, and a savings of $235,000 resulted from a $5,000 research investment in bridge guard rails -- a 47-1 ratio!(3-4)

Examination of the bounds for the examples provided above does not provide a reliable indication of "value." For example, if one extrapolates to a $10 million research investment, the "benefit" would vary between $50 million and $470 million -- not a bad return on an investment! Obviously, this is an oversimplified approach for assessing the value or benefit and should not -- and cannot -- be assumed to be the value of research. In fact, implementing research in many cases leads to increased costs, apparently reducing the dollar value of research although other benefits -- increased safety, reduction in loss of life, and reduced delays -- would be realized.

However, one can say that a $25 million investment (my estimate of 1991 bridge research expenditures) in bridge-related research translates to a 0.3-percent investment relative to the estimated $8.2 billion annual cost required to eliminate existing and accruing deficiencies. The research relative to the total estimated national expenditure rate of $5 billion translates to a 0.5-percent investment rate. These investment rates are woefully inadequate, regardless of how value or benefit is perceived. Research can and has provided the technology to reduce existing and accruing deficiencies. Research will also provide the technology to construct more durable, maintenance-free structures. However, this technological development will be slow in coming at current investment rates.

In creating Title VI of the Intermodal Surface Transportation Efficiency Act of 1991, Congress focused, for the first time, on the important role that research plays in providing the technology to improve the efficiency of the highway system. Even so, research expenditures for highway bridges and related structures will, at best, increase by a factor of about two. Again, if research is to close the technological and funding shortfalls, additional research investment will be required.


Advanced composites will be used to extend the service life of existing construction and to provide durability of new construction. Shown here is the column strengthening of a bridge column on the Santa Monica freeway in Los Angeles. This technology uses carbon toes that are wound around the column to increase seismic resistance. The technology was developed with Technology Reinvestment Project funding and FHWA participation.

(Photo courtesy of the Univ. of California at San Diego)



We are facing ever-increasing technical and fiscal challenges to ensure that accruing problems and deficiencies in the nation's inventory of bridges can be eliminated. At best, it is difficult to quantify the value or benefit that bridge research provides to close the funding and technological gap to eliminate deficiencies. Specific examples of research can be documented to verify that research pays off. In many instances, however, research provides partial solutions that require further research. When that occurs, it becomes more difficult to quantify the value of research. In addition, benefits must include indirect factors, such as the impact that research has on reducing delays and, thus, travel time.

The value of bridge research cannot be measured by any single yardstick. It can be concluded that placing a value on research is more of an art than a science. Yet, history clearly demonstrates that the development and implementation of innovative bridge technology has been a key to the economic development of the country and, thus, leads us to the future.

From one perspective, technology is available today that can be used to reduce deficiencies in today's bridges. From a practical perspective, appropriated funding is inadequate to accomplish the job. However, if technology is to advance, allowing more effective use of limited funds, the highway community must first collectively define a "value of research" that is easily understood by the public; champion public support for the conduct of the research; and, finally, identify alternative funding strategies to support the research. The key to the future is the united voice of the highway community championing the cause of research.

Table 1 -- Status of the Nation's Bridges(1)

Bridge Inventory 575,583 (100%)
Backlog of Deficient Bridges 199,277 (35%)
Structurally Deficient 118,563 (21%)
Functionally Obsolete 80,714 (14%)
Cost to Eliminate Current Deficiencies $78B  
Average Annual Cost to Maintain Status Quo $5.2B  
Average Annual Cost to Eliminate Existing and Accruing Deficiencies $8.2B  
Estimated Current National Expenditures $5.0B  
Replacement/Rehabilitation (ISTEA) $2.7B  
Other Federal-aid, State, and Local Funds $2.3B  
Research Investment ?  


  1. The Status of the Nation's Highways, Bridges, and Transit: Conditions and Performance, Federal Highway Administration, Washington, D.C., January 1993.
  2. Highway Bridge Replacement and Rehabilitation Program, Eleventh Report of the Secretary of Transportation to the United States Congress, Federal Highway Administration Draft, Washington, D.C., April 1993.
  3. TR News, No. 153, Transportation Research Board, Washington, D.C., March-April 1991.
  4. TR News, No. 150, Transportation Research Board, Washington, D.C., September-October 1990.

James D. Cooper is the chief of the Structures Division, Office of Engineering and Highway Operations Research and Development, at the FHWA's Turner-Fairbank Highway Research Center in McLean, Va. He received his bachelor's degree and master's degree in civil engineering from Syracuse University. He is a licensed professional engineer in the District of Columbia.

Eric Munley is a research structural engineer in FHWA's Structures Division. Since 1989, he has directed the Structures Division's research program in Composite Materials and Structural Adhesives. He received a bachelor's degree in civil engineering from the University of Connecticut in 1974 and a master's in engineering mechanics from Cornell University in 1993. He is a licensed professional engineer in Connecticut.