Post-Fire Behavior of GFRP Bars and GFRP-RC Slabs

Technologies developed over the last two decades have introduced the use of glass fiber reinforced polymer (GFRP) composite bars as reinforcement in concrete structures when corrosion of the steel reinforcement is likely to occur. Fire resistance of GFRP-reinforced concrete (RC) members is a potential concern that needs to be understood and addressed because of the susceptibility of GFRP bars to degradation at elevated temperatures. In this study, the residual strength of fire-exposed GFRP-RC slabs and the GFRP mechanical properties after furnace exposure were studied. Slabs reinforced with two different types of GFRP bar were exposed to a furnace fire and sustained three-point bending, simulating the sustained service load (the moment due to dead load plus 20% of the moment due to live load at midspan), for 2 h. Upon completion of the fire test, the residual slab strength was assessed using a quasi-static flexural test up to failure. Next, GFRP bars were extracted from the selected locations of the slabs to evaluate the residual mechanical properties, including shear strength (transverse and horizontal) and glass transition temperature (T-g). The GFRP-RC slabs with both bar types did not experience apparent reduction in flexural capacity after a 2-h fire test that generated a maximum temperature of 115 degrees C at the bar surface. The GFRP transverse shear strength decreased whereas the horizontal shear strength and T-g slightly increased. (c) 2017 American Society of Civil Engineers.