ABSTRACT

Over 40 percent of the bridges in the United States need repair, strengthening, or replacement. Due to budget constraints, many states are forced to post load restrictions on their bridges as a temporary measure. Fiber reinforced polymers (FRP) provides an economical and practical solution for repair/strengthening of highway bridges. In Missouri, a number of bridges have been repaired/strengthened with Carbon FRP composites. The latest are three bridges located in Boone County. The bridges were constructed in the 1970s. Constant increase of traffic volume and the use of heavier trucks demanded an upgrading of these bridges to withstand HS20 truck loading. Their simply supported decks were designed according to the American Association of State Highway and Transportation Officials (AASHTO). Analysis using the current AASHTO code indicated that the reinforced concrete (RC) channels of their decks require upgrading for flexure and shear. Using FRP composites a lower cost solution was achieved due to speed and ease of their installation that involves minimal labor and reduced traffic interruption. Strengthening design was achieved using the classical approach utilizing compatibility of strains and equilibrium of internal forces. Elastic load tests were conducted on two of the bridges before and after strengthening to evaluate their performance. This paper reports on the strengthening techniques, design approach, and elastic testing of the three bridges.