The Federal Highway Administration (FHWA) says that $53 billion is needed just to maintain the current state of our bridges, of which a great percentage is rated as being deficient. To improve on the situation, $72 billion in added investment is needed. A breakdown of the number of deficient and obsolete bridges in each state is provided in this issue (see New York's Tops List of States Whose Bridges are Most in Need of Repair, 11/96).
Aside from its funding foibles, there is cause for optimism and excitement in the bridge industry. New procedures, designs and materials are pushing the industry forward. In a recent conversation with Mike Abrahams, manager of complex steel structures and movable bridges for Parsons Brinckerhoff, he shared some thoughts on what he thought were some of the major trends in today's bridge market.
The design/build method of bridge design and construction was his No. 1 issue. "We are seeing this with increased frequency and popularity, particularly with large and complex structures," he said. "We see more and more requests for proposals coming out from agencies.
"It seems to solve a lot of the institutional and administrative issues that tend to bog a project down. If it's done properly, the energies spent on the project are spent on getting the design done and getting it built." There is discussion about what is the best procedural method for performing such projects and the method of payment to consultants who submit designs for such contracts.
No. 2 on Abrahams' list is the new load resistance factor design (LRFD) specification being issued by the American Association of State Highway & Transportation Officials (AASHTO). "It is starting to work its way into use," Abrahams said. "It seems to be on a slower time table than design/build." Most states are opting to continue to use the more familiar AASHTO standard spec rather than the LRFD. To familiarize the industry with the LRFD spec, firms, such as HDR Engineering and Parsons, are developing courses on the new spec.
Abrahams' No. 3 choice is metrication. The conversion to the metric system continues to be the subject of much discussion as the industry wrestles with the choice between hard and soft conversion (see Consulting Engineers Ponder Merit of Highway Industry Metrication, April 1995). "I think [metrication] took a step back recently because the rebar spec was changed back to a soft conversion [after initially having been hard converted]," said Abrahams.
According to Abrahams, cable-stayed design is the dominant design for larger bridges, and has been for some years. "Segmental-concrete or concrete-box girders also are a popular design," he said.
In the area of bridge coatings, moisture-cure urethanes (MCUs) are finding their way into use in many areas of the country. According to Bill Brinton Jr., specification specialist with Wasser High-Tech Coatings, Kent, Wash., his company's coatings have been applied to more than 1,500 bridges in more than 30 states since first developing it's MCU in conjunction with the Oregon DOT nearly nine years ago.