Shear Capacity of Reinforced Concrete Beams at Elevated Temperatures

Fire safety is an important design aspect that ensures structural integrity of a Reinforced Concrete (RC) building during fire events. As new codes are moving from prescriptive methods to performance-based methods, design engineers are in need of rational design tools to assess the capacity of RC elements during a fire event. Previous research work focused on the flexural and axial capacities of concrete elements exposed to fire. Research addressing the shear capacity of concrete elements exposed to fire is limited in the literature. An analytical method to predict the shear capacity of RC beams exposed to elevated temperatures is proposed. The method assumes that shear capacity can be derived using existing ambient temperature methods while accounting for the effect of elevated temperatures on material properties. It involves heat transfer analysis, evaluation of the material properties at elevated temperatures, and application of the Modified Compression Field Theory (MCFT) to estimate the shear capacity. A parametric study is then conducted to investigate the effects of different parameters on the shear capacity of RC beams exposed to fire. A simplified practical tool that can be used by design engineers to predict the shear capacity of RC beams exposed to elevated temperatures is proposed. Simple equations to calculate the average temperatures of the shear reinforcement and the concrete cross-section are the base for this tool. A set of design charts to determine the average temperature of shear reinforcement and concrete are also provided