More than 250,000 deficient or obsolete structures, such as bridges and parking garages, need repair, retrofit or replacement in the U.S. alone. This need has stimulated development of a number of composite enabling technologies. Exhibiting corrosion resistance, light weight (approximately one-fifth the weight of steel), high strength and ease of installation, composite materials are gradually being accepted as alternatives to traditional materials to reduce dead load and extend structure life. Glass, glass/aramid hybrids and carbon fibers, used with epoxy resin, continue to find application as cost-effective column-wrapping and jacketing systems for seismic and structural upgrading (see “Composites Repair”). Fiberglass composites are finding niche applications in areas such as stay-in-place concrete forms, reinforcing rebar, bridge decks, wind fairings and enclosures as well as entire bridges.

 Carbon fibers are finding other niches as well, particularly in precast concrete products, such as those provided by Chomarat North America (Anderson, S.C.) for architectural cladding, insulating sandwich panels, hardwall panels and double tees.

Governments and engineering associations worldwide are cooperating to standardize workable international design parameters, and the composites industry is forging critical alliances with the civil engineering community and associations. A notable example is the American Concrete Institute (ACI), which recently (September 2008) published three new guides for concrete reinforcement: ACI 440.2R-08: Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures; ACI 440.5-08: Specification for Construction with Fiber-Reinforced Polymer (FRP) Reinforcing Bars; and ACI 440.6-08: Specification for Carbon and Glass Fiber-Reinforced Polymer (FRP) Bar Materials for Concrete Reinforcement.

Bridge decks, a continuing focus of composites development, have been dominated by glass-fiber-reinforced pultruded components. A notable recent entry is the ZellComp two-piece bridge system, developed by ZellComp Inc. (Durham, N.C.). This system avoids several installation issues associated with previous one-piece solid or sandwich panel composite deck designs. Modular, flat bottom sections with vertical T-section flanges go down first and are easily fastened to the superstructure with shear studs or structural clips. Then, top sheets go down in narrow-width sections that make it easy for installers to fasten them mechanically through the T-shaped flanges. ZellComp bridges have been installed to date in Tangier Island, Va. and in Bradford, Vt.

Notably, the American Association of State Highway and Transportation Officials (AASHTO) has just released a new document, The Guide Specifications for Design of FRP Pedestrian Bridges, 1st Edition, which applies to FRP composite bridges intended to carry primarily pedestrian and/or bicycle traffic. The new document provides specifications relating to the use of FRP for design loads and design details.