Shear performance tests and theoretical analysis of self-tapping screw connection in light gauge steel-timber composite structures

Self-tapping screw connections effectively inhibit wood cracking and enhance the transverse tensile and longitudinal shear capacities of timber, and are widely used in steel–timber composite structures. The interfacial slip behavior is a key factor influencing the mechanical performance of such composite members. This study investigates the shear performance and degradation mechanisms of light-gauge steel–timber connections using self-tapping screws. Monotonic and cyclic loading tests are conducted on single-screw connections fabricated with fast-growing poplar plywood and oriented strand board (OSB). The effects of wood type, panel thickness, and steel plate thickness are systematically examined. Results show that the dominant failure mode is the ductile embedment of the screw head into the wood panel. Compared with poplar plywood connections, OSB connections exhibit increases of 7.8 % in bearing capacity, 5.1 % in initial stiffness, and 12.6 % in ductility, owing to a more homogeneous microstructure. Increasing the steel plate thickness from 1.2 mm to 2.0 mm significantly enhances the initial stiffness by 46.3 %, extends the yield plateau, and raises the ductility coefficient by 151 %. Under cyclic loading, the connections display pronounced degradation, with the bearing capacity decreasing by 24–36 % compared with monotonic loading, the average strength degradation reaching approximately 65 %, and the stiffness degradation coefficient attaining 45 %. Furthermore, a modified theoretical model accurately simulates the nonlinear load–slip behavior, demonstrating its good applicability for the analysis of such connections. This work provides key parameters and a theoretical basis for the refined simulation and performance evaluation of light-gauge steel–timber screw connections in lateral-force-resisting and seismic design.