Seismic performance of CFST superimposed shear walls with different shear connections

The synergistic integration of concrete-filled steel tube (CFST) columns and composite shear walls addresses the strategic requirements of the modern construction industry’s shift toward building industrialization and intelligent construction. This paper introduces a new type of concrete-filled steel tube with superimposed shear walls (CFST-SSWs), which can be conveniently installed on-site to improve construction efficiency and quality. The column-to-wall connection significantly affects the quality of CFST-SSWs. Three full-scale CFST-SSW specimens and one full-scale cast-in-place column composite shear wall specimen with different types of end columns and shear connectors were experimentally tested under constant axial forces and lateral cyclic loads to investigate their seismic performance. The findings indicate that all specimens exhibited flexure-dominated behavior. The X-shaped crack in the CFST-SSWs only extended to the edge of the superimposed wall, whereas that of the cast-in-place concrete column composite shear wall connected to a crack in the end column, demonstrating the CFST-SSWs specimen’s superior seismic performance. Three connection types (shear studs, U-shaped rebars, and hooked rebars) provided reliable connections and ensured efficient shear transfer. The shear studs demonstrated superior performance after the specimen yielded, particularly in the post-peak load stage. Numerical models were developed to predict the CFST-SSW’s lateral stiffness. Experimental data were used to validate the model’s accuracy.