Behavior of stud connections in steel-concrete composite structures under freeze-thaw cycles

Freeze-thaw cycles (FTCs) significantly affect the safety and serviceability of steel-concrete composite structures in cold regions. In this study, the behavior of stud connections in steel-concrete composite decks subjected to FTCs is studied. The failure modes, shear strength, shear stiffness, and load-slip responses of the stud connections after FTCs are experimentally investigated, considering the influences of the number of FTCs, water-to-binder (W/B) ratio, stud diameters, and freeze-thaw medium (FTM). The results indicate that after FTCs, the failure mode of the stud connection is primarily governed by the concrete slab due to significant material degradation. Exposure to 50 and 100 FTCs results in shear strength reductions of 26.0% and 34.0%, respectively, with further degradation observed when seawater is used as FTM. Reducing the W/B ratio is shown to be a promising strategy for enhancing the shear performance of the stud connections after FTCs, while increasing the stud diameter demonstrates a relatively limited effect. Additionally, finite element models are developed and validated, and a parametric study is conducted to investigate the effects of concrete material properties. Furthermore, analytical equations are proposed to provide a useful reference for estimating the interfacial strength and stiffness of composite connections after FTCs, and their applicability is evaluated through comparisons with the experimental results.