Shear stability and resistance design of novel vertically-flexible stiffened steel plate shear walls

Steel plate shear walls (SPSWs) have been widely employed in practical engineering projects. The steel plates inevitably endure axial loads due to the gravitational forces and structural settling. However, vertical pre-compressive loads have detrimental effects on the buckling behavior and shear resistance of the steel plates. Instead of strengthening the SPSWs to resist the vertical loads, a new type of vertically-flexible stiffened steel plate shear wall (VFS-SPSW) is proposed to minimize these adverse effects. The incorporation of hollow steel tube reduces the vertical compressive stiffness of the VFS-SPSW, leading to a decrease in the proportion of axial compressive loads transmitted to the steel plate wall from the boundary frame. Consequently, this feature facilitates the installation of VFS-SPSW without the necessity of awaiting the completion of the upper structure. In this paper, finite element (FE) analysis is conducted to obtain a threshold out-of-plane bending stiffness ratio for the stability of the VFS-SPSW. Subsequently, a formula for threshold out-of-plane bending stiffness ratio is proposed, including parameters of the ratio of torsional to bending stiffness and aspect ratio of the subpanel. Then, the anchoring mechanism of hollow steel tube to the tensile field of the steel plate is investigated. The threshold in-plane anchor stiffness ratio is defined to ensure the full development of the tension field in the steel plate. A formula for predicting this ratio is proposed by theoretical and numerical analysis. Finally, the reduction factor of vertical compressive stiffness for the VFS-SPSW at the threshold in-plane anchor stiffness ratio is calculated. The results indicate that the vertical compressive stiffness of the VFS-SPSW, which meets the threshold stiffness design requirements, can be decreased to below 50% of the traditional stiffened SPSW, while ensuring that the reduction in ultimate shear stress remains within the limit of 5%.