Residual Post-fire Strength of Shear Studs in Composite Beams with Solid Slabs

Composite steel-concrete beams are employed in buildings and bridges, which may experience elevated temperatures in case of fire. The residual capacity of composite members that survive fire depends on the performance of their shear connectors. This study investigates the capacity of shear studs in composite floors with no metal deck after experiencing elevated temperatures. A 3-D nonlinear finite element model of composite push-out specimens was developed. The model was subjected to the ISO-834 standard fire followed by a cooling-down phase, after which displacement-controlled loading was applied to the model until failure. After validating the model based on experimental data, a parametric study was conducted, in which the load-slip behavior of members employing different concrete compressive strengths, slab thicknesses, shear stud heights, stud diameters, and maximum experienced temperatures was investigated. The thickness of the concrete slab was found to have a noticeable effect on the strength of shear studs before and after heat exposure. The AISC specifications, while overestimating the capacity of unheated shear studs in many cases, were found to underestimate the residual strength of shear studs when used with post-heating mechanical properties. A simplified equation was proposed for quick determination of residual strength of shear studs, which may be used for post-fire structural assessment.