Vulnerability Vulnerability Analysis Of FRP Strengthened Continuous Beam Bridge Based On Performance

As the throat of traffic,the safety construction and good operation of bridge have been widely concerned by the society.A large number of existing highway bridges in China have the problem of insufficient seismic capacity.As a lifeline project,once the bridge is damaged by earthquake,it will cause huge direct and indirect economic losses in a short time.Because of its obvious technical advantages,FRP externally bonded reinforcement is widely used in reinforcement engineering.In view of the fact that most of the researches on FRP seismic strengthening of piers use pseudo static test to analyze the hysteretic response from the point of view of the resistance of the specimens,the difference of seismic response of the specimens strengthened with FRP is not considered.Therefore,the vulnerability curve is used to evaluate quantitatively the impact of FRP reinforcement on the seismic performance of bridge structure from the perspective of probability.The main research contents are as follows:(1)This paper collects the research status of FRP seismic strengthening at home and abroad,and summarizes the existing problems and deficiencies in the previous research.At the same time,it introduces the development of vulnerability theory and its research status in reinforcement work,and puts forward the purpose and main content of this paper.(2)The theory of performance-based seismic vulnerability analysis is introduced from three aspects: seismic response analysis,division of structural performance level and establishment of vulnerability curve.This paper expounds the selection of seismic intensity index and the definition of seismic performance design parameters,compares two analysis methods(IDA method and cloud chart method)of probabilistic seismic demand model,introduces the drawing method of theoretical seismic vulnerability curve,and compares the advantages and disadvantages of frequency statistics method,linear fitting analysis method and capacity demand curve fitting method.(3)The constitutive relation of materials and the calculation theory of fiber model are introduced.Based on the existing test data,a numerical model of pier column is established by using Open SEES software.The quasi-static analysis of the numerical model is carried out,and the hysteretic curves of numerical simulation and test data are compared to verify the reliability of the modeling method.(4)Based on a continuous beam bridge,a finite element model is established according to Open SEES software.The model is compared with Midas model periodically to verify the reliability of the numerical model.The response analysis of pier column is carried out by using IDA analysis method,and the linear regression analysis of seismic demand parameters and seismic intensity parameters is carried out to obtain the probabilistic seismic demand model.The limit value of quantitative index of seismic performance level is determined by pushover analysis.On this basis,the vulnerability curve before and after strengthening is obtained to evaluate the strengthening effect of FRP.(5)The difference of exceedance probability of pier columns before and after FRP seismic strengthening under different performance levels was compared under different reinforcement ratio,reinforcement ratio,concrete strength and axial compression ratio.The vulnerability curves of the piers strengthened with FRP under different parameters are compared,which can be used to improve the old bridge.