Error Estimation of Nonlinear Equivalent Static Analysis for 3D-BRB Frames

Abstract

Capacity Spectrum Method (CSM) as a nonlinear equivalent static method is one of the practical procedures which is usually used to estimate the seismic demands for design and evaluation of structural systems. This paper proposes a nonlinear equivalent static method called MPA-MCSM which combines the Modified Capacity Spectrum Method, MCSM, and the Modal Pushover Analysis, MPA. The accuracy of the developed algorithm is investigated for response prediction of Buckling Restrained Brace (BRB) frames with irregularities in elevation. The accuracy assessment of the proposed method is evaluated based on the computation of four seismic demands; peak roof displacement, story drift, base shear and story shear for each considered structure. The accuracy of MPAMCSM responses is checked against the results obtained from nonlinear time-history analysis. Thirty different models consist of 3-, 9- and 20-story structures subjected to 7 pairs of ground motions were analyzed. The results reveal that MPA-MCSM provides conservative seismic demands and has a good accuracy for BRB frames.