Experimental study on CFSC encased shear connectors in steel-concrete composite joints with UHPC grout

This paper presents a summary of results of an experimental investigation to assess the behavior of shear connectors encased in concrete-filled steel cells (CFSCs) that are used in steel-concrete joints with ultra-high performance concrete (UHPC) grout. In this study, a total of ten push-out specimens: including two plug-in type specimens and eight CFSC type specimens have been conducted. The slip between the steel plate and concrete and the strains for the steel studs and transverse rebar were measured and analyzed. Results obtained from the present and previously reported experiments showed that the average ultimate and residual bond strengths at the steel/concrete interface increased by 20% and 36%, respectively, as compared with specimens without confinement. Furthermore, experimental results indicated that providing a steel cell increased the ultimate strength of PBL in CFSC by 29%, as compared with unconstrained counterparts. The performance of the steel studs and transverse steel rebar were barely influenced by steel cells confinement. In comparison with the cases of shear connectors singly used, the interactions between the steel studs and PBL in CFSC decreased the shear capacity of the steel studs by 18% and increased that of PBL by 6%. A comparison between experimental and analytical results obtained from existing formulations indicated that the PBL shear capacity with confinement was underestimated when using analytical formulations that do not consider the confinement effects.