Design Approach for Short-Term Deflection of Simple and Continuous Steel–Concrete Composite Beams Considering Interface Slip

Due to the slip occurring at the interface between the steel beam and the concrete slab, accurately predicting the deformation behavior of steel–concrete composite beams is rather complicated. In this paper, a mechanics-based yet simplified design approach is proposed to determine the short-term service deflection of simple and continuous composite beams. First, analytical solutions for the interface slip-induced strain of composite beams under positive moments are derived. On this basis, a multifold line is assumed to represent the distribution of the slip strain, which is then used to derive the effective flexural stiffness of the composite beams. Considering the interface slip effect and the tension stiffening effect in the reinforced concrete slab, a design equation for the effective flexural stiffness is formulated for the composite beams under negative moments. Finally, a design recommendation for the deflection calculation of continuous composite beams is proposed. By comparing the predictions with available experimental results from 57 simply supported beams subjected to positive moments, 14 simply supported beams subjected to negative moments, and 15 continuous beams, it is found that the proposed approach is more consistent and accurate than the design guidelines or models considered in this study.