Capacity Design of Vertical Boundary Elements in Steel Plate Shear Walls

Design requirements now appear in the 2005 AISC Seismic Provisions for Structural Steel Buildings (AISC, 2005b), referred to herein as The Provisions, for steel plate shear walls (SPSWs) that are designed such that their web plates buckle in shear and develop diagonal tension fi eld action when resisting lateral loads. Energy dissipation and ductility during seismic events is principally achieved through yielding of the web plates along the diagonal tension fi eld. Consistent with capacity design principles, The Provisions require that the vertical and horizontal boundary elements (VBEs and HBEs) of SPSWs, as shown in Figure 1, be designed to remain essentially elastic with the exception of plastic hinging at the ends of horizontal boundary elements. The commentary of The Provisions provides some guidance on how to achieve this requirement. However, the methods described in the commentary, as shown in this paper, do not necessarily lead to VBEs that meet the requirement of essentially elastic behavior under the forces generated by fully yielded web plates. This paper reviews the current approaches provided in The Provisions commentary for determination of capacity design loads for the VBEs of SPSWs and also describes how the capacity design objective may be achieved using nonlinear static analysis. Then, a new procedure is proposed that uses a fundamental plastic collapse mechanism and linear beam analysis to approximate the design actions for VBEs of SPSWs for given web plates and horizontal boundary member sizes. The proposed procedure does not involve nonlinear analysis, making it practical for use in design. VBE design loads are estimated using both the current and proposed procedures for two example SPSW confi gurations. The resulting design loads are then compared with the VBE design loads as determined by nonlinear pushover analysis.