Capacity design of intermediate horizontal boundary elements of steel plate shear walls

Consistent with capacity design principles and requirements of ductile behavior, the 2005 AISC and 2001 CSA seismic design codes require that the intermediate horizontal boundary elements (HBEs) of steel plate shear walls (SPSWs) be designed to remain essentially elastic with the exception of plastic hinges at their ends when the infill plates fully yield under seismic loading. However, the unexpected failure observed during the tests on a full-scale two-story SPSW suggested that the current design approach does not necessarily lead to an intermediate HBE with the expected performance. This paper presents analytical models for estimating the design forces for intermediate HBEs to reliably achieve capacity design. Those models combine the assumed plastic mechanism with a linear beam model of intermediate HBE considering fully yielded infill panels and are able to prevent in-span plastic hinges. Design forces predicted using the proposed models are compared with those from nonlinear finite element analysis. Good agreement is observed. Finally, the proposed models are also used to explain the observed premature failure of intermediate HBE.