Influence Mechanism of Steel-concrete Interlayer Partial Shear Connections on Mechanical Properties of Composite Girders

A reduction in composite action using a partial shear connection (PSC) in the hogging moment region of a steel–concrete bridge can mitigate the concrete tensile cracking risk while maintaining the structural ultimate bearing capacity. To date, specific mechanical effects, important for the establishment of evaluation theory, have not been studied. To this end, four girders and six push-out specimens were tested for the effect investigation. Numerical analysis with material damage plasticity models and an analytical study were conducted for parametric and mechanistic investigations. The push-out test results showed that a wrapping rubber sleeve reduced the shear stiffness of the stud by 91.9%, whereas its strength varied slightly. The girder test results showed that arranging rubber sleeved stud (RSS) connectors in the composite girders reduced the girder load-carrying capacity and bending stiffness by 17% and 12%, respectively. Moreover, the concrete tensile cracking performance was improved. The analysis results showed that, for reducing the concrete tensile stress, the RSS connector in the girder had a more favourable effect on prestress distribution than increasing the ordinary stud spacing. In addition, an evident stress concentration appeared when the stud distance was increased. According to the analytical analysis of the girder under negative bending, the concrete tensile stress is exponentially related to the interlayer stud stiffness, and the exponential is expected to be 5/3. The research revealed the detailed mechanical behaviour of the girder with a PSC and simultaneously compared the effects of the two PSC methods. This research will help establish design and evaluation methods for PSC action.