Investigation of the bending strength of glass fiber-reinforced polymer (GFRP) bars exposed to thermal stress

Nowadays, the utilization of composite reinforcement instead of steel rebars in construction is considered as an alternative and many methods are being intensively studied on composite bars. The superior tensile strength, lightness, corrosion resistance, and long service life of GFRP composite reinforcements have made them a strong competitor to steel rebars. Reinforced concrete structures constitute a large part of the existing building stock in Turkey and around the world. Therefore, composite bars have the potential to be widely utilized. This study investigates the flexural strength of GFRP composite bars after exposure to distinct thermal stress. In the study conducted, 47 GFRP bar bending specimens with a length of 150 mm and a diameter of ϕ10 mm were tested with a 3-point bending test after the thermal process was completed until GFRP bars reached the ultimate load-carrying capacities. During the experiments, GFRP bars were exposed to 9 distinct temperature loads: 22°C, 100°C, 150°C, 175°C, 200°C, 225°C, 250°C, 300°C, and 500°C, respectively. As a result of the tests performed, GFRP bars reached the highest bending load value at 200°C, which is 13% higher than the average of the reference specimens tested at 22°C room temperatures. It is seen that in possible situations such as fire, the load-carrying capacity of GFRP bars will start to decrease after 200°C, and at 500°C, the resin completely melts, and the GFRP bars lose their rigidity and strength. When the average deflection values of the GFRP bar specimens are compared for 22°C and 300°C, a 35% reduction was calculated at 300°C.