Seismic force demand on RC shear walls for direct displacement-based design

This article aims to investigate seismic force demand on RC shear walls which are designed using direct displacement-based design (DDBD) method. For this purpose, first 12 shear walls were designed using DDBD approach and then were modeled nonlinearly in OpenSees using fiber section elements. Each wall was subjected to 45 artificial ground motions and the seismic force demand, including the shear force and the bending moment, were determined along the wall height. The nonlinear dynamic analysis results indicated that the seismic force demand was significantly amplified relative to the design forces. This amplification, which was due to the higher mode effects, is mainly a function of structural period and ductility demand. To find new shear and moment envelopes for capacity design, two envelop shapes compatible with internal force pattern along the wall height were selected. Then, the required equations were presented for envelope parameters based on the regression analysis of the results. The comparison of seismic force demand with proposed and previous envelopes indicates the superiority of new proposed envelopes for DDBD approach.