Experimental investigation on fatigue behavior of composite beams with different studs arrangements

Abstract

Connections between steel beams and concrete slabs that reduce the number of shear connectors by using studs with a larger size or partial shear connections could be advantageous by reducing installation time and provide additional working space for construction workers to move on the top steel flange. In this paper, steel and concrete composite beams with different headed stud shear connector arrangements were tested under fatigue loading to evaluate the crack patterns in concrete slabs, deformations, and strains in the composite sections and shear connectors. These arrangements included full shear connections achieved by 22.2 mm and 15.9 mm diameters headed stud connectors arranged in one and two rows, respectively, and a partial shear connection with two rows of 15.9 mm diameter shear connectors. Distributing the required resistance of shear to a larger population of smaller studs produced more beneficial behavior over that of a smaller population of larger diameter studs. The concrete slab fully shear connected by the one-row arrangement experienced longitudinal cracks during fatigue loading, which led to more stiffness degradation and strength deterioration, while such cracks were eliminated in the two-row arrangement. Therefore, 77.1%, 177.7%, and 152.5% increase in the incremental deflection, slippage, and studs’ strains, respectively, were obtained for this specimen. Moreover, reductions of 83.0% and 66.7% were obtained in the composite action in terms of the cyclic slippage for the specimens with the one- and two-row arrangements, respectively. Final residual static tests up to failure were conducted to explore the residual behavior of the fatigued specimens. Degradations in the residual stiffness and strength of the fatigued specimens occurred and more partially composite effects were obtained, which led to higher residual strains in the headed stud connectors and extreme fibers of the composite sections of 12.6% and 16.6%, respectively.