Flexural Performance of RC Beams Strengthened with Polyester FRP Composites

In this study, cost-effective polyester fiber reinforced polymer (PFRP) composite plates were used as external strengthening materials of conventional reinforced concrete (RC) beams. The flexural behavior of PFRP strengthened RC beams was investigated. Two RC control beams and six PFRP strengthened RC beams were constructed and tested under four-point bending. The dimension of these concrete beams used was 150 mm x 300 mm x 2000 mm. The experimental variables included thickness of PFRP (four and six layers of laminates) plates and steel reinforcement ratio (0.223 and 0.503%). The test results indicated that compared with the control beams, the strengthened beams experienced significant enhancement in ductility, ultimate load and deflection due to the PFRP reinforcement. The increase in transverse load due to PFRP strengthening was more pronounced for the RC beam with a low steel reinforcement ratio (0.223%). The ductility (calculated from both displacement-based and energy-based approach) of the PFRP strengthened RC beam with the low steel ratio was larger than that of the strengthened beams with the large steel ratio. The experimental ultimate loads of the PFRP strengthened beams were also compared with the predictions based on the equation given in ACI 440.2R-08 proposed for RC beams strengthened by synthetic glass or carbon FRP materials. This study, therefore, implied that the PFRP has potential as external strengthening materials of concrete structures.