Current engineering practice uses nonlinear static pushover analysis to evaluate seismic response of any lateral load resisting system. In the pushover analysis, both the force distribution and the target displacement are based on the assumptions that the response of the structure is controlled by the fundamental mode of vibration and the mode shape remains unchanged. Both of these assumptions have limitations and may affect the accuracy of the analysis results. Recently, modal pushover analysis procedure has been developed to improve conventional pushover procedures by including higher-mode contributions to seismic demands. Similar to the conventional pushover procedure, the modal pushover analysis method is simple and computationally attractive. However, for any structural system, the accuracy of the modal pushover analysis procedure must be evaluated to identify any conditions that might be applied for seismic evaluation of that structural system. In this paper, the accuracy of modal pushover analysis procedure in estimating seismic demand in steel plate shear wall systems is evaluated. Two steel plate shear walls (one 4-storey and one 15-storey) designed according to the capacity design approach are considered in this study. A nonlinear finite element model is used for all the analyses. Results, such as interstorey drift ratios from the modal pushover analyses are compared with those from more accurate nonlinear seismic analyses.
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