Overall stability of concrete-encased steel plate shear walls with rebar truss connectors under axial compression

A novel concrete-encased steel plate shear wall with rebar truss connectors, termed CSPWT, was proposed to improve the composite action between the steel plate and the surrounding concrete to develop favorable load-carrying. By forming a spatially integrated restraint system with the reinforcing mesh, the rebar truss connectors effectively restrain the relative slip and separation between the steel plate and concrete, thereby enhancing the steel-concrete composite action. Owing to the relatively thin sections, the stability performance of CSPWT becomes a governing factor in structures with large story heights. In this investigation, therefore, the overall stability performance of CSPWT was investigated through experimental testing, finite element analysis (FEA), and theoretical derivation. Two full-scale specimens with height-to-thickness ratios ranging from 15 to 18 were tested under axial compression, and both exhibited overall instability failure. Based on the validated finite element model (FEM), parametric analyses were conducted to investigate the effects of parameters on the elastic buckling load and elastoplastic overall stability performance of the CSPWT. According to the results, the height, thickness, and width of the wall, as well as the concrete strength, would significantly affect both the elastic buckling resistance and the elastoplastic overall stability capacity, while the latter was additionally influenced by the web rebar diameter, the initial imperfection amplitudes, and the rebar truss spacing. Based on the test results of the two specimens and the FEA results, formulas were proposed for calculating the elastic buckling load and elastoplastic load of the CSPWT under axial compression. Furthermore, a design method for the φ-λ n curves under axial compression was established, providing references for the axial compression stability design of CSPWT and similar composite shear walls.