Study On Simplified Analysis Method And Seismic Fragility Of Curved Bridge

With the development of society,curved bridges play a more and more important role in the transportation network of modern cities.Especially,with the large-scale construction of curved viaducts and overpasses,curved bridges have become an integral part of urban transportation networks.The damage of the curved bridges in the earthquake hazard will significantly affect the traffic-carrying capacity of the urban traffic network,and delay the post-earthquake rescue and relief.The seismic fragility analysis is an important technology to understand and assess the seismic capacity of the bridge structures,and has been widely used in the areas of seismic engineering and disaster mitigation.However,comparing to the straight bridge,the curved bridge has more complex structure,and the seismic response and seismic fragility analysis of the curved bridge is more difficult.At present,the traditional finite element analysis is cumbersome in establishing the whole structure and cost a large amount of time to analyze due to the huge elements of the structure.Therefore,this method is not suitable for rapid model and damage assessment of the urban traffic network.In response to these problems,this paper studies the simplified modeling method and the seismic fragility of curved bridge.The main contents of this paper are as follows:(1)Based on the fiber section element,the curved bridge nonlinear finite element model is built by using the finite element analysis software OpenSees,the response characteristics of curved bridge under different directions and different intensity ground motions input are calculated by numerical simulation analysis.The response of key components such as the pier top,pier bottom and bearings are studied.(2)The failure criterion and the structural damage index of curved bridge are studied.Based on the analysis of the moment – curvature,displacement ductility of the pier section and the deformation of the bearings,the curvature ductility ratio of the pier bottom,the displacement ductility ratio of the pier top and the deformation of bearings are studied as parameters of the curved bridge damage index.(3)Based on spring-bar model,a simplified modeling method of curved bridge is studied by using rigid bar,flexural springs,shear springs and torsional springs.The relations between the complex finite element model and the simplified analysis model is established.Compared with the fiber element model,the computation time of the simplified curved bridge model can be shortened by 30%.(4)The seismic vulnerability of the curved bridge is analyzed by using the simplified model and choosing the displacement ductility ratio of the pier top as the damage index.The study shows that the longitudinal vulnerability of the curved bridge is greater than the transverse,and the pier height is the key parameter that affects the disaster-resisting performance of the structure.