Steel plate composite shear walls with 100 MPa concrete and spiral-reinforced boundaries

Abstract

This study introduces an innovative spiral-confined concrete-filled steel plate (SCCFSP) composite shear wall that is designed to improve ductility through spiral reinforcement in boundary elements, particularly when high-strength concrete is used. The seismic behavior of SCCFSP composite shear walls was evaluated and compared against two other configurations: (1) walls with tie bars and no boundary elements and (2) walls with stiffeners and concrete-filled steel tube (CFST) columns acting as boundary elements. The test specimens were subjected to a constant compressive axial load and reversed cyclic lateral load. The test results show that the ultimate drift ratio and cumulative energy dissipation of the specimen with stiffeners and CFST columns increased by 55 % and 220 %, respectively, compared to the specimen with tie bars and no boundary elements. The ultimate drift ratio and cumulative energy dissipation of the specimen with spirals in the boundary elements further increased by 61 % and 80 %, respectively, compared to the specimen with stiffeners and CFST columns. A numerical model of SCCFSP composite shear walls was developed to establish the relationship between the ultimate cross-section curvature and spiral details, such as the effective confinement index and spiral configuration length. A design algorithm was also developed to iteratively determine the (a) minimum effective confinement index, (b) minimum spiral length satisfying axial compression ratio, and (c) ultimate drift ratio limitations. Based on numerical simulations of 176 SCCFSP wall sections, simplified formulas are proposed to calculate the minimum effective confinement index and spiral configuration length of spirals within SCCFSP composite shear walls.