Performance Analysis of Frames with Cyclic Loading Pushover Method Based on Multi-modal
|Keywords||Performance-based seismic design Cyclic loading Pushover Analysis method based on multi-modal Nonlinear Dynamic Time-history Analysis Single-degree of freedom system The Hysteretic Energy|
The plastic deformation might be developed in the elements or structures of seismic frame under the strong earthquake action. As a simplified analysis method of nonlinear response of the structure, pushover analysis has been become one of the most widely used method in performance-based seismic analysis. One-way loading mode is only considered in traditional pushover analysis and sequential loading until structure damage to obtain the equivalent SDOF system capacity spectrum, combined with seismic demand spectrum to evaluate the seismic performance. The loading modes of traditional Pushover method are unilateral loading modes, which can not take full account of the cycle loading history, duration and cumulative damages. For the traditional Pushover method having the above-mentioned shortcomings of the important factors in seismic response, the cyclic loading pushover method to simulate the real ground motions and the method of determining target displacement during cyclic loading are suggested. In this paper, cyclic loading Pushover analysis method is proposed on the traditional Pushover method, because cyclic loading Pushover analysis method can consider the cycle loading history and indicate the cumulative damage of structure. The analysis steps are: the framework of multi-degree of freedom system is converted to equivalent single degree of freedom elastoplastic systems respectively in accordance with the first and second modes. The original MDOF and the equivalent SDOF are analysised by nonlinear dynamic analysis method respectively. The equivalent peak time-history displacement calculated by time-history displacement from the equivalent SDOF is composed and linearized to be the time-history displacement which to be used in the cyclic loading Pushover analysis method based on multi-modal. The results show that the curves of the equivalent peak time-history displacement of structure are similar to the peak time-history displacement of the original structure. The summits of time-history displacement curves considered the second mode are more precise than only considered the first mode in a higher level of structures. This article adopts SAP2000 structural analysis software to realize multi-modal cyclic loading Pushover analysis method and introduces the link unit that provided by SAP2000. Because it has non-linear element hysteresis behavior, link unit provided by SAP2000 is used to simulate the nonlinear characteristics of structural elements. Pivot hysteresis model used to be component restoring force model can be achieved relatively good results. The displacement and hysteretic energy dissipation of the plane frame structures are acquired from the multi-modal cyclic loading Pushover analysis, traditional Pushover analysis and dynamic tine-history analysis. By comparing the results of the three analysis methods, the cyclic loading Pushover analysis method considered two modes proposed in this article can be better evaluated seismic performance of structures under the cycle loading earthquake. The conclusions of performance analysis of frames by the method of Pushover with cyclic loading based on multi-modal in this article will provide a reference for nonlinear static analysis method in seismic analysis.