| China is at the confluence of the three plates so that our country is a seismically active country.Bridge structures are very important parts in lifeline systems,however they are vulnerable.Once the destruction of bridge structures occurs,it will seriously affect the disaster relief work.On the other hand,the large scale of construction of bridges promotes economy development.Therefore,whether it’s from the view of earthquake relief or the development of economy construction,it is necessary to do research on seismic vulnerability of bridges.This dissertation is concentrated on a concrete-filled steel tube arch bridge with a span of 460 m.To analyze the bridge’s vulnerability curves,the main tasks on this subject are as follows:1.On the basis of reviewing literature,the definition of the seismic vulnerability was introduced.And the theories and main methods for seismic vulnerability analysis of bridges were concluded.2.The construction of fragility curves was presented and summarized.The selection of seismic waves and the damage index were discussed in detail. Based on this, a decision was made regarding the curvature ductility ratio was used for the damage index of seismic vulnerability analysis.3.The finite element model of the large span concrete-filled steel tube arch bridge was established by means of the finite element analysis software ANSYS.Its dynamic characteristics were analyzed at the same time. Then Using Peak Ground Acceleration(PGA) as the ground motion intensity index,the nonlinear dynamic time history of the transverse and longitudinal direction of the bridge was carried out.4.According to the Moment-Curvature analysis,the threshold value of the damage index was quantified.5.Using traditional reliability method to establish the theoretical fragility curves, and then using numerical simulation method to prove the feasibility of traditional reliability method.6.With other conditions unchanged,the influence of seismic wave input method was discussed. |
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