FLEXURAL BEHAVIOR OF RC BEAMS STRENGTHENED WITH FRP COMPOSITE SHEETS SUBJECTED TO DIFFERENT LOAD CASES

This study was carried out to experimentally investigate the flexural performance of RC beams strengthened with GFRP and CFRP composite sheets for three cases: strengthening before loading, strengthening while subjected to service loading and strengthening after unloading.. The parameters of study included level of loading and the type of FRP strengthening system. The test program consisted of seven groups of beams. The first group was unstrengthened control group. The remaining six groups were divided into two series, one was strengthened with GFRP sheets, and the other was strengthened with CFRP sheets. Each series consisted of three groups; the first one was strengthened before loading, the second group was loaded to service load, unloaded, repaired with FRP sheet then loaded to failure, and the third group was similar to the second one except that the beam was strengthened while loaded. These beams were tested in flexure and the experimental data on strength and deflection was obtained. The results show that the use of FRP sheets as an external reinforcement to strengthen or repair concrete structural members (uncracked or precracked) is very effective. The test results also reveal that the beams loaded to service load levels, unloaded and then repaired with FRP sheets and those strengthened while loaded behaved in a similar way as those strengthened before loading