Seismic Resilience Assessment Of Long-span Deck Concrete-filled Steel Tube Arch Bridge

As a common type of highway bridge in China,deck long-span concrete-filled steel tube(CFST)arch bridge is greatly affected by earthquake disasters.In order to avoid excessive earthquake losses and casualties and ensure that the main functions of the bridge are not interrupted,it is particularly important to maintain a high level of resilience of the structure under the action of earthquakes,especially strong earthquakes.Therefore,it is of great significance to study the seismic resilience level of such structures.With reference to FEMA P-58 and the Standard for seismic resilience assessment of buildings,this paper develops the seismic resilience evaluation process applicable to long-span concrete-filled steel tube arch bridge,and takes a long-span concrete-filled steel tube arch bridge as the research object to carry out seismic resilience evaluation based on earthquake intensity.The specific research contents and conclusions are as follows:(1)Based on the design parameters of a solid bridge in southwest China,a longspan concrete-filled steel tube arch bridge is designed.The finite element model of the arch bridge is established,and the model is verified by modal analysis.The nonlinear response of the structure is analyzed by selecting suitable ground motion records under four intensities of earthquakes,namely,frequent earthquake,fortification earthquake,rare earthquake and very rare earthquake,and the structural response under different seismic levels is obtained.(2)The seismic fragility analysis of long-span arch bridge structure is carried out.To select the appropriate EDP for the arch bridge structure,the overall collapse fragility and component fragility of the bridge are studied.The main components of the whole bridge are divided into finite groups for the calculation of seismic losses of subsequent structures.For each defined fragility group,the corresponding quality grade level and evaluation basis are given.(3)The seismic loss analysis and seismic resilience rating of the structure are carried out.Based on the current seismic resilience evaluation standards in China and the differences between the bridge structure and the building structure in the aspects of function and repair logic,the seismic resilience indexes of the structure under different seismic levels were evaluated,and the seismic resilience grade of the long-span arch bridge was evaluated.Based on the above evaluation results,some suggestions are put forward to guide the seismic resilience design of long-span concrete-filled steel tube arch Bridges.(4)The results show that when the intensity of ground motion is small,the loss of non-structural components is relatively large,but the proportion of the increase of ground motion intensity is gradually decreasing.The situation of structural components is just the opposite,and the casualties start from the intensity of rare earthquakes.The structural members have a great influence on the seismic resilience of long-span arch bridge structure,which is the main factor causing the seismic loss of the structure.The influence of the structural members on the seismic resilience is highlighted in the maintenance time,especially under the action of strong earthquakes.The final rating of the structure is 1 stars,in which the maintenance time is the key index affecting the comprehensive seismic resilience grade of the long-span arch bridge.It is concluded that it is the key to realize the rapid recovery of bridge floor traffic function after earthquake.In order to improve the comprehensive seismic resilience of such structures,the seismic resilience design can focus on the structural components that have a great influence on the maintenance time.