Revisiting the Ambient and Postfire Strength of Channel-Type Shear Connectors

Abstract

The ability of steel-concrete composite floor systems to withstand loads relies on shear connectors, which prevent or limit slip between the two materials. This paper presents an experimentally validated numerical investigation along with parametric studies aimed at evaluating the behavior of channel-type shear connectors in ambient and postfire conditions. A three-dimensional finite-element model of a push-out test was developed, which incorporated the nonlinear material properties of steel and concrete in ambient conditions as well as their thermomechanical properties to simulate heating and cooling and the effects of fire exposure. The model was validated using experimental data obtained by the authors and those from previous studies. Subsequently, a parametric study assessed the load-slip behavior of the channel-type connectors assuming different compressive strengths of concrete, slab thicknesses, connector dimensions, and maximum temperatures experienced. The failure mode in ambient and postfire conditions was observed to be affected by the length, web thickness, and height of the channel, but not by its flange thickness. The numerical results, combined with an analytical investigation of failure mechanisms, were then used to develop an improved design equation for channel-type shear connectors, which performs noticeably better than current design provisions in comparison with experimental data.