Behavior of CFSC-Encased Shear Connectors in Steel-Concrete Joints: Push-Out Tests

Abstract

A concrete-filled steel cell (CFSC) is commonly used in steel-concrete joints of hybrid girders. The performance of shear connectors embedded in CFSCs has been investigated in the current study in which a series of push-out tests were performed in order to assess the mechanical behavior of a perfobond strip connector (PBL) and headed steel studs. The failure modes, load-slip relations, load-strain relations, and the influence of the push-out test arrangement on such behaviors are presented and discussed in this study. Comparisons between the current experimental results and those presented in previous studies by the authors demonstrate that the average peak bond and residual bond strength at the interface between the perforated steel plate and the concrete in CFSC are 1.0 and 1.4 times higher than those derived from the plug-in type of push-out specimens (PI type), respectively. Moreover, it is found that the steel cell confinement has little impact on the performance of the transverse steel rebars of the PBL and the behavior of steel studs. Because the confinement provided by the steel cell is able to improve the shear capacity of the concrete dowel in the PBL, the ultimate shear capacity of the PBL encased in CFSC is 31% higher than that of the PBL without confinement. It is also discovered that the ultimate strengths of the PBL and the steel studs fabricated in CFSC could not be reached at the same time. Furthermore, the experimental results are compared to the shear resistances predicted by the available analytical equations for the PBLs without confinements. It is found that the ultimate shear resistances of the PBLs under the confinement are underestimated by the existing equations.