Fatigue Tests on Steel–Concrete Composite Beams Subjected to Sagging Moments

Abstract

Current shear stud fatigue capacity recommended for design of shear connectors is based on experimental data from push-out tests, and there is a need to experimentally evaluate the fatigue performance of shear connectors in steel-concrete composite beams. Therefore, this paper presents the results of four composite beams tested under fatigue with different degrees of shear connection. The fatigue testing was carried out to a million cycles under bending with two different amplitudes. The residual strength of steel-concrete composite beams was evaluated by performing static tests until failure after the completion of the fatigue tests for each of the specimens. The testing measurements included midspan deflection, slippage between the steel beam and concrete deck, shear connector strains, and strains in the concrete deck and bottom steel flange. Based on the experimental results, degrees of the shear connection between the steel beam and the concrete deck played a major role in controlling the longitudinal fatigue cracks in the concrete deck. The residual deflection and plastic slippage increased as the fatigue of cycles increased. This is caused by the damage in the concrete deck that developed around the shear studs, which led to a reduction in the composite stiffness. The shear connectors’ strain ranges gradually increased due to the accumulation of damage as the number of cycles increased. Based on the results of this paper, it is concluded that the current shear stud fatigue design curve predicts a lower fatigue life for the shear connectors.