Behavior of steel tube-reinforced concrete composite walls subjected to high axial force and cyclic loading

This paper proposes an innovative composite shear wall, named the steel tube-reinforced concrete (ST-RC) composite wall, with steel tubes embedded at the wall boundary elements and fully anchored within the foundation. This arrangement is supposed to enhance the wall’s seismic performance. A series of quasi-static tests were performed to examine the behavior of the ST-RC walls when subjected to high axial forces and lateral cyclic loads. The area ratios of steel tube and of concrete filled steel tube (CFST) (i.e. the ratios of the cross-sectional areas of steel tubes and of CFSTs over that of the wall boundary element, respectively), axial force ratio, and cross-sectional shape of walls were taken as major test variables. All specimens failed in a flexural mode, characterized by tensile yield of the vertical rebars and steel tubes in the boundary elements and compressive crushing of concrete at the wall bottom. The test results showed that the ST-RC composite walls had larger load-carrying and deformation capacities relative to the RC wall counterpart. The deformation capacity of the rectangular-shaped composite walls increased with an increase in the area ratios of steel tube and of CFST and decreased with an increase in the applied axial force ratio. The barbell-shaped composite wall that was configured with edge columns had much larger deformation and energy dissipation capacities than the rectangular-shaped composite walls. In addition, simplified formulation was proposed to evaluate the lateral load-carrying capacity of the ST-RC composite walls. The evaluated results showed good agreement with the test results, with errors no more than 10%.