Performance Evaluation of a New NSP for Estimation of Seismic Demands of Nonlinear Irregular BRB Frames

Nonlinear static procedures are commonly used to compute seismic demands of structural systems. This paper combines the modified capacity spectrum method (MCSM) and modal pushover analysis (MPA) and proposes a new nonlinear static method called MPA-MCSM. To evaluate the accuracy of the proposed method, 30 different buckling-restrained braced (BRB) structures which consist of 3-, 9- and 20-story BRB frames with irregularities in plan and in elevation are selected. Each structure was analyzed subjected to seven pairs of ground motions. As a measure for the performance assessment of the proposed method, four structural seismic demands: (1) peak roof displacement, (2) story drift, (3) story shear and (4) base shear, are computed for each considered structure. The accuracy of MPA-MCSM responses is checked against the results obtained from nonlinear time-history analysis (NL-THA). The results reveal that MPA-MCSM provides conservative seismic demands for BRB frames.