EFFECTS OF BARS SLIPPAGE ON THE PREAND POST-HEATING FLEXURAL BEHAVIOR OF FRP REINFORCED CONCRETE BEAMS: EXPERIMENTAL AND THEORETICAL INVESTIGATIONS

Using fiber reinforced polymer (FRP) bars as an alternative to traditional steel reinforcement solves durability problems in reinforced concrete structures. This study investigated the effects of bar slippage on the pre- and post-heating flexural response of concrete beams reinforced with different FRP and conventional steel bars. A total of twenty-four control and heat-damaged concrete beams with different FRP/steel bars were loaded (in triplicates) under a four-point loading configuration to evaluate their mechanical performance and failure modes while acquiring strains in tension steel and compression concrete. A new theoretical method was proposed to predict the load capacities of the beams with consideration of slippage between the FRP bars and surrounding concrete. The results were then compared with the load capacities computed using the ACI code that assumes a prefect bond between FRP bars and concrete. The post-heated concrete beams failed at a relatively low load capacity. They also presented an increase in deflection and ductility and a decrease in stiffness and total absorbed energy. The theoretical ultimate load of the FRP-RC beams, computed on the basis of the ACI code, was overestimated relative to the corresponding measured values. By contrast, the computations based on the actual pre- and post-heating mechanical properties of the FRP bars and concrete and their bond characteristics provided reasonably reliable results