Improvement Of Energy Balance Based Multi-Mode Pushover Analysis Method

Performance-based Seismic Design represents the development tendency of modern earthquake resistant design. Nonlinear static analysis method (Pushover analysis) is the key analysis method, which has caused many attentions of researchers and engineers and been widely used in the practical engineering due to its conceptual simplicity, computational efficiency and satisfying accuracy. However, the previous research showed that the conventional pushover curve may reverse in higher modes. Thus, energy balance based pushover analysis method was proposed to overcome this problem. In this paper, an improvement of the energy balance based multi-mode pushover analysis (EMMA) method is focused with two-stage load patternsFirstly, the research status, basic formulations, implementation steps and load patterns of the nonlinear static analysis methods are introduced, and the difficulties of pushover analysis method is also discussed.Secondly, four kinds of typical nonlinear static analysis methods are presented, including the equivalent linearization method, N2Method, modal pushover analysis and energy balance based multi-mode pushover analysis method. Then, the seismic response of a9-story plane frame building is evaluated by the above4nonlinear static analysis methods, whose results are compared with those by the nonlinear response history analysis. The merit and demerit of the four methods are also discussed.Finally, the energy balance based multi-mode pushover analysis (EMMA) method is improved by considering the redistribution of inertia forces after yielding structural components. On one hand, the proposed method keeps the advantage of EMMA method to estimate the higher modal responses with elastic assumption for computational efficiency. On the other hand, the variation of inertia forces as structure yields is taken into account. The errors of the proposed method and the original one are investigated and compared by calculating a9-story plane frame structure and a20-story space frame structure under four different ground motions, from which the contribution to the accuracy of the proposed method is demonstrated.