Fragility Analysis Of SDOF Based On Pushover Method

Fragility analysis of civil engineering structures has been a very popular topic both at home and abroad. Fragility analysis results of structures not only can be used to evaluate the seismic capcity of structures before nature disaster, but also contribute to compareing reinforcement schemes of existing structures. Fragility curves are widely applied in seismic fragility analysis. Nonlinear time-history analysis is considered as the most reliable method to develop fragility curves. However, the computational effort involved in this method is excessive. Then, a research project on seismic fragility analysis based on pushover analysis is performed in this paper. The main contents are as follows:1. In order to compare the differences between results with different Pushover procedures, pushover analysis and nonlinear time-histoty analysis are performed for a SDOF under generated sine wave, seismic wave fitted from code response spectrum as well as recorded EL-centro wave and Tang-shan wave. Considering results of nonlinear time-history analysis as benchmark, differences of Pushover procedures are obtained by comparing results of pushover analysis with that of nonlinear time-history analysis based on different restoring force models.2. Many recorded seismic motions are selected. Nonlinear time-history analysis and elastic time-history analysis are performed under these selected seismic waves. Pushover analysis is performed for the same SDOF based on the elastic acceleration response spectrum which is developed by elastic time-history analysis. The relationship between results of pushover analysis and nonlinear time-history analysis is investigated by statistical analysis, and the influence of uncertainties in ground motion is considered in this paper.3. SDOF structures, with mass, stiffness and yield force following normal distribution, are developed by Monte-Carlo method. Pushover analysis is performed for the developed structures. For results obtained by Pushover analysis, statistical analysis is conducted. The statistical distribution of the results is obtained.4. A method is proposed in this paper to predict the fragility of SDOF based on Pushover analysis. The fragility results predicted with proposed method and Monte-Carlo method are compared.5. Design examples of prestressed concrete continuous rigid frame bridges and corroded reinforced concrete bridges are provided to illustrate the application of seismic fragility analysis based on pushover analysis proposed on this paper.