Residual Flexural Stiffness Calculation of T-RC Beams Considering the Effect of Fire

Abstract

T-shaped reinforced concrete (T-RC) beams are widely used in high-rise buildings due to their advantages of reduced concrete usage, low sectional stress, and decreased weight of the structure. However, the calculation method of residual flexural stiffness of T-RC beams has limited existing research. To address this knowledge gap, a comprehensive experimental investigation was conducted, comprising fire tests, dynamic tests, and static load tests on 10 T-RC beams. The aim was to analyze the effects of fire time and load ratio on the residual flexural stiffness of composite beams. The experimental results showed that the residual flexural stiffness of T-RC beams decreased with increasing fire time and load ratio. However, the impact of fire time was more significant than the load ratio. A refined finite element model of T-RC beams under high temperature and after high temperature was established by modifying the frequency data of the dynamic test and considering the impact of cracks. The model accurately predicted the temperature field and deflection change of T-RC beams under fire. Furthermore, a method for calculating the residual flexural stiffness of T-RC beams considering the effect of fire was proposed and validated against the measured values. The proposed method demonstrated a low error rate of less than 10%.