The Structural Behaviour of Composite Beams in Fire Considering Interface Slip and Uplift Effects

Abstract

Fire is one of the most devastating disasters in the world. Composite construction in steel and concrete has gained popularity in recent years. The shear connection between the steel joist and the concrete slab is the structural component which enables the composite action to develop. This thesis will carefully investigate the structural behaviour of shear studs and composite beams at elevated temperatures. The major works in this study are as follows: First, push-out tests of shear studs embedded in solid slabs, composite slabs with open trapezoidal steel sheeting and steel bar truss floor slabs at several temperature levels were conducted, and three-dimensional finite element model comprising both thermal and mechanical analysis was developed, and validated with the test results. Based on the analysis on the existing test results and parametric study result, equations were proposed to predict the shear capacity and the load-slip relationship models of shear studs embedded in different slabs at elevated temperatures. Second, fire tests were conducted to study the fire performance of composite beams with steel bar truss floor slabs considering both the beams designed as full and partial shear connection at room temperature. Three-dimensional finite element model comprising both thermal and mechanical analysis was then developed considering the non-linear load-slip relationship of shear studs for the different beam-floor arrangements including solid slabs, composite slabs with steel sheeting perpendicular and parallel to the steel joist, and composite slabs with steel bar truss floor slabs. Then, an extensive parametric study was conducted with the verified model to further study the influence of shear studs. Finally, design suggestions were presented to consider the influence of shear connectors in building applications based on the analysis and comparison between the existing results and design methods in different codes.