SEISMIC STRENGTHENING OF REINFORCED CONCRETE BRIDGE PIER WITH FRP COMPOSITES

摘要

In-situ lateral load tests were conducted on Interstate 15 to determine the strength and ductility of an existing concrete bridge. The bridge was designed and built in 1962 for gravity and wind loads; as such, it did not possess adequate reinforcing details for seismic resistance. The purpose of the tests was to examine the improvements that can actually be achieved using a carbon Fiber Reinforced Polymer (FRP) composite retrofit. Three tests were conducted; the first test was on an as-built bent (Bent #5); the second test was on an as-built bent (Bent #6) which was retrofitted with FRP composites for seismic strengthening; and the third test involved repair of Bent #5, FRP retrofit and testing. The paper presents analysis of the results of the as-is (Bent #5) and retrofitted (Bent #6) tests. The design of the FRP composite was developed based on rational guidelines for the columns, cap beam, and cap beam-column joints to provide a specific displacement ductility. Agreement between analytical and experimental results was observed which included the peak lateral displacement of the bent, the peak lateral load, and the locations of the plastic hinges. The FRP composite was able to strengthen the cap beam-column joints effectively for an increase in shear stresses of 35 percent, while the peak lateral load capacity was increased by 16 percent. The displacement ductility was improved from 2.8 for the as-is bent (Bent #5) to 6.3 for the retrofitted bent (Bent #6), which exceeded the retrofit objective of doubling the ductility. The tests demonstrated that reinforced concrete (RC) bridge bents which were designed without any seismic detailing can be rehabilitated effectively with FRP composites. The advantages of FRP composite rehabilitation include cost effectiveness, fast construction, minimum traffic disruption, and superior strength per unit weight.