Capacity design for composite partially restrained steel frame-reinforced concrete infill walls with concealed vertical slits

This paper presents an innovative capacity-based design procedure that aims to achieve the ideal seismic performance for the composite partially restrained (PR) steel frame-reinforced concrete (RC) infill wall with concealed vertical slits (PSRCW-CVS). The proposed method adopts the direct capacity design principles and preselected preferred plastic mechanism such that the RC infill wall undergoes ductile failure prior to the other steel components in the event of a rare-level earthquake (i.e., earthquake with a 2% probability of exceedance in 50 years). Based on the ultimate resisting capacity of RC infill walls, the free-body diagrams and simplified design formulae for the surrounding steel components, including the vertical boundary element (VBE), horizontal boundary element (HBE), PR connection, and shear connectors, were proposed. To demonstrate the reasonability of the capacity-based design procedure, a five-story PSRCW-CVS structure was designed according to the proposed design method, followed by a series of nonlinear time history analyses. The overall seismic response of this example was evaluated in terms of story displacement, interstory drift ratio, residual story displacement, and residual interstory drift ratio. The proposed method yielded a more uniform interstory drift ratio distribution along the height of the five-story PSRCW-CVS structure. Structural damage was controlled by achieving the preselected preferred plastic mechanism.