STUDY ON EARTHQUAKE RESILIENCE ANALYSIS AND OPTIMIZATION FOR URBAN BRIDGE NETWORK SYSTEM BASED ON NSGA-II ALGORITHM

Urban bridges are important infrastructure that affects regional economy and social community. When subjected to strong earthquakes and other disasters, the seismic performance of urban bridge structures, especially the resilience of the transportation system composed with key bridges, are very important to social stability and regional economy development. In recent years, the seismic resilience had attracted the attention of researchers. To incorporate the recoverable performance and the resiliency measurement into the evaluation and optimization of the seismic performance of a bridge system, there are still many issues to be studied. This paper further quantitatively analyzes the post-earthquake recovery process, residual function, idle time and repair time, and their influence on the resilience index. And the performance assessment process of urban bridge system was developed. According to the different damage states of the bridge, the resiliency indexes, the repair time, the economic loss after the earthquake and the recoverability of different recovery strategies are calculated. The model of the post-earthquake recovery process is proposed for quantitatively evaluating the recovery stratigies. The resilience is included in the evaluation framework of the seismic performance of the urban bridge system, and the post-earthquake recoverability evaluation framework of the urban bridge system is proposed so that decision makers with different risk-bearing capabilities can make decisions on different recovery processes. The post-earthquake economic loss, resiliency and pre-earthquake repair/reconstruction cost are used in conjunction with the multi-objective optimization algorithm, NSGA-II, to seek a pre-earthquake resilience improvement strategy for the help of selecting maintenance or resilience improvement measures. The calculation of the proposed method is given as an example, which provides new ideas for improving the seismic resiliency of urban bridge system.