Resilience Analysis And Decision-Making Of Bridges Considering Aftershock Hazard

The performance-based seismic design theory has been tremendously developed during the past few decades.However,with the rapid economic growth in China,large cities and urban agglomerations have densely populated infrastructures,people and social wealth.The current seismic design is gradually transferring from simply focus on structural earthquake safety to focus on the ability of post-earthquake structures,cities and even the entire society to maintain or quickly restore functionality,namely,the Seismic Resilience Design.Research on seismic resilience analysis is still in its infancy.Due to the interdisciplinary and comprehensive application involved,it has a certain degree of complexity.There is still a long way to go before the formation of a more widely accepted seismic resilience analysis method.Meanwhile,since earthquakes usually consist of a number of seismic sequence,very few research has involved in extending the theory and method of urban seismic resilience analysis from resisting one earthquake to resisting multiple earthquakes including aftershocks.Therefore,based on the probabilistic performance seismic analysis framework,this study focuses on the resilience analysis framework and decision making of bridge considering aftershock hazard.The main research contents and conclusions of this study are as follows:Firstly,proposed the concept of generalized resilience by expanding the traditional quantitative definition of resilience based on functionality.The generalized resilience analysis and decision-making theoretical framework considering aftershock hazard is established,and the analysis methods of each part are studied one by one.Secondly,introduced and discussed the aftershock hazard analysis model based on the Omori law.The Monte Carlo-based aftershock hazard analysis method is establishing by simplifying the occurrence rate of aftershocks from non-homogeneous Poisson distribution to 0-1 distribution.In addition,the as-recorded mainshock-aftershock sequence database was established,and the difference in frequency spectrum between the mainshocks and aftershocks was investigated.Thirdly,modified the current aftershock fragility analysis framework based on specific damage states in terms of two aspects.The optimal theory-based B2B-IDA method for aftershock fragility analysis based on a certain damage state is proposed,which can significantly reduce the computational work while improve accuracy necessarily.On another hand,a deterioration finite element numerical modeling method for conventional type bridges,and a mixed damage index named MBDI as well as its quantitative method are proposed.A quasi-static test as well as a shake-table test are conducted to validate the proposed deterioration modeling method.A bridge is taken as a case study,and the aftershock fragility analysis based on specific damage state is conducted using different damage index as EDP.The results shows that the proposed deterioration modeling method is able to simulate the deterioration behavior under cyclic loading and also seismic sequence.In addition,MBDI is a more effective EDP for aftershock fragility analysis compared to other displacement-based damage indices.Therefore,the proposed method can effectively improve the accuracy of aftershock fragility analysis results.Fourthly,conducted research on the time-variant aftershock fragility analysis method.The closed-form formulas for event-dependent aftershock fragility are developed based on the Markov transition theory and aftershock fragility curves based on damage states.By combining it with aftershock hazard analysis,the Monte Carlo-based time-variant aftershock fragility analysis framework is established.The method is utilized to the case study bridge to calculate the time-variant probability the probability for each damage state,the time-variant aftershock fragility and the time-variant probabilistic seismic capacity(PSC)of the structure.It is found that during the first year after the mainshock,the PSC significantly decreased over time,which indicate that it is necessary to consider the influence of aftershocks to seismic demand during seismic design process.Fifthly,conducted research on the analysis method of post-earthquake generalized resilience recovery curves for conventional bridge.The procedure for generalized resilience recovery curves is established which 4 stages including determining repair methods,repair costs,repair time,and recovery functions.For the case study bridge.The deterministic generalized resilience recovery curves of each decision variable under different damage states and different repair methods are analyzed.It is found that the proposed method effectively solve the problem of the non-synchronization of seismic capacity and functionality recovery progress.In addition,it also successfully considers the influence of different pier repair methods on the total structural repair cost and the post-repair seismic capacity.Sixthly,carried out generalized seismic resilience evaluation and decision-making of conventional bridges considering aftershock hazard.The method for probabilistic time-dependent curves for each decision variables during aftershock seismic sequence is establish.Based on that,the generalized resilience assessment and decision-making method considering aftershock hazard is developed.The proposed method is utilized to the case study bridge.The decisions are made through the input-output relationship analysis of all the possible restoration strategies on different levels of resilience,including engineering resilience,functionality resilience,and economic resilience.The results shows that the proposed resilience analysis method effectively considers the impact of different pier repair method to the seismic capacity during aftershock sequence.In addition,the input-output based decision-making method considerably optimizes the choice in terms of repair timing and repair method,which enables to satisfy the target seismic resilience at the lowest repair cost.Finally,the conclusions of the study are summarized and the remaining questions for further investigation are highlighted and discussed.