Effect of High-Temperature Exposure on the Residual Capacity of Steel-Concrete Shear Connectors: Experimental Study

Composite steel-concrete beams are widely used in flooring and decking systems in buildings and bridges due to their efficiency. High-temperature exposure is a major hazard that can affect the composite action of such beams and, hence, their capacity to carry loads. An experimental program is conducted to investigate the effect of heat exposure on the residual carrying capacity of different types of shear connectors. A total of 8 specimens made of different configurations of shear studs and shear angles were tested till failure at room temperature and after high-temperature exposure. An electric furnace is utilized to apply controlled high temperature around the specimens and then the residual capacity was evaluated using direct shear force through push-down tests. The experimental results showed consistently that high temperature reduces both stiffness and capacity of the shear connector. When compared to predictions from building codes, the Eurocode was found to severely underestimate the residual capacity for shear connectors by nearly 50% for the shear studs and nearly 20%-28% for the angle connectors. The American standards also did underestimate the residual capacity by however a lesser percentage than the Eurocode. The reason for this underestimation can be attributed to the fact that the room-temperature design equations are already conservative and that the effect of temperature is overestimated using a single lumped reduction factor for the material strength. The experiments are also modeled and reproduced using high-fidelity coupled-field finite-element model where sequential thermal-structural analysis is conducted and the temperature-dependent nonlinear characteristics in both material and deformational properties are incorporated. The findings from the numerical analysis agreed with the experimental results.