Performance Evaluation of RC Beams Strengthened with an Externally Bonded FRP System under Simulated Vehicle Loads

Carbon fiber-reinforced polymer (CFRP) sheets can be used to strengthen existing RC bridge girders/decks. The objective of this study is to investigate whether transient vehicle loads present during the installation of CFRP influence the bond performance between the CFRP and the concrete substrate and, therefore, the consequent strengthening effect. A total of eight RC beams were tested. Two were unstrengthened reference beams, five were strengthened with CFRP sheets while subject to transient loads, and the final beam was strengthened with CFRP sheets while subject to only a sustained static load. The test parameters included the amplitude of the transient load, the anchorage length of the CFRP sheets, and the reinforcing/strengthening ratio. The transient loads were continued for 2 days (during CFRP cure) before all five CFRP-strengthened RC beams were tested to failure in four-point flexure. The test results were compared with those of the reference beams and the one strengthened under a sustained load. It was shown that a 1-Hz sinusoidal transient load varying between 30 and 50% of the ultimate capacity of the unstrengthened beam during the installation and curing of the CFRP sheets does not affect the structural performance of CFRP-strengthened RC beams. This result demonstrates the applicability of the fiber-reinforced polymer (FRP) strengthening technique for bridge girders that are subjected to continuous vehicle loads.