Interfacial shear behavior in steel-concrete-steel composite structures with stud connectors after freeze-thaw cycles

Steel-concrete-steel (SCS) composite structures have potential applications in the northern cold region. To investigate the interfacial shear performance and failure mechanism of SCS composite structures with stud connectors subjected to freeze-thaw cycles (FTCs), freeze-thaw tests and push-out tests were conducted on 36 specimens to investigate the effects of concrete type, stud quantity, and FTCs. The test results showed that when the core concrete was changed from C30 concrete to ultra-high-performance concrete (UHPC), the shear capacity, shear stiffness, and ductility of the specimens all increased significantly, by approximately two times. Moreover, the failure mode of the specimens shifted remarkably from concrete splitting damage to stud breakage failure. Increasing the stud quantity or FTCs reduced the shear capacity and stiffness of the specimen, yet it exerted a minimal impact on the ductility. In addition, precise finite element models were established to investigate the effect of the relative strength between studs and concrete and the stud spacing on the failure modes and interfacial shear capacity. Based on experimental and finite element data analysis, a formula for calculating the interfacial shear capacity of SCS composite structures after FTCs was proposed. The calculation results were consistent with the test and simulation results, and this formula can serve as a reference for the design and application of SCS composite structures in cold regions.