Shear behavior of stud connectors in steel bridge deck and ballastless track structural systems of high-speed railways

Steel bridges with ballastless tracks have been increasingly used in high-speed railways (HSRs). This kind of steel bridge deck and ballastless track structural system can be considered a steel and multilayer concrete composite structure (SMCCS). However, rare information is available about the shear behavior of stud connectors embedded in the SMCCS. To address this research gap, it was extensively investigated through push-out tests and finite element (FE) analyses in this research. Three groups of experiments including a total of nine push-out specimens with single-layer or double-layer concrete slabs were performed, and the failure mode, load-slip curve, shear capacity, and shear stiffness were presented and discussed. Refined three-dimensional nonlinear FE models were established and verified using the push-out tests. Based upon the FE models, the shear behavior of stud connectors in the SMCCS was further studied, and the effects of key variables on the shear behavior of studs were discussed. Moreover, the design shear capacities of stud connectors calculated using the current design codes were evaluated, and the design recommendations were presented. The results indicate that double-layer concrete slab and group effect will reduce the shear performance of studs. The stud diameter and yield strength have a significant effect on the shear behavior of studs. The shear performance of studs improves with the increasing stud diameter and yield strength. Lower shear strength of the concrete-concrete interface will cause the interface cracking of the push-out specimen, which occurs before the stud shear failure. The results can provide essential data for future analysis and design of steel bridges and ballastless tracks for HSRs.