Psha-Based Bridge Seismic Fragility Analysis And Conectivity Reliability Analysis Of Network

China has a large number of standard span highway simple supported beam bridges, which usually have the same classification about seismic fortification and the seismic design usually according to the unified seismic parameter zonation (USPZ) of China, the result of USPZ are always different with that of seismic microzonation using the method of probability of seismic hazard analysis (PSHA). The differences generate the irregularity of the bridges structural fragility even in same intensity zone, which make it difficult to evaluate the network connectivity. As an example, a highway network covering three zones of seismic intensity is taken to present the frame work of network seismic fragility analysis. The probability of network nodes closing corresponding to difference earthquake level are evaluated using structural fragility analysis, on the basis of that, the network connectivity for these seismic reoccurrence interval is evaluated by algorithm Order-X. The framework presented could serve for the network seismic hazard forecast and decision optimization for bridge retrofitting. The specific steps are as follows:1. According to the PSHA method, the ground motion parameters of the studied area are obtained, and the artificial seismic waves are generated by the random signal simulation based on ARMA.2. Two different nonlinear finite element models are considered, namely the fiber model and the improved I-K plastic hinge model, which are used to modeling the reinforced concrete bridge piers respectively. The fiber model and the improved I-K plastic hinge model are analyzed under low reversed cyclic loadding, and the analysis results are compared with the test values of the bridge piers to find out the difference, which was the base to adjust and calibrate the parameters of each model respectively.3. Dynamic time-history analysis was carried out to reinforced concrete bridge pier, which are based on the fiber model and the improved I-K plastic hinge model respectively, compare the difference between the two calculation results; The effects of these differences on the fragility of bridge structure and the calculation results of the connectivity reliability of road network are analyzed. The results show that:The inherent difference between the two models has little effect on the calculation results of road network connectivity reliability, demonstrate the rationality of the application about the improved I-K plastic hinge model and analyzes the advantage of the plastic hinge model in the cost of computer calculation.4. The structure model mentioned above inputted the simulated ground motion, which is generated by the first step. The failure probability of each bridge about the function of normal operation is obtained based on the different levels of performance. The failure probability of each bridge will acted as network nodes close probability into the network connectivity analysis model to get road network connectivity reliability. Reinforce the bridge contained in each line of network respectively, and the relationship between the degree of improvement about connectivity reliability of road network and reinforcement cost was analyzed to determine the priority reinforcement route, so that the decision makers can reasonably allocate resources for road network reinforcement.The results obtained in this paper have some practical significance for the traffic capacity prediction after earthquake, risk estimation and strengthening investment decision of the regional highway bridge network.