Seismic Performance Assessment Of Continuous Beam Bridge Based On Total Probability Method

In the seismic performance evaluation of reinforced concrete continuous girder bridge,there are problems such as inappropriate choice of Engineering Demand Parameters(EDP)and ground Intensity Meature(IM),insufficient consideration of the effect on structural randomness,and insufficient applicability of decision indicators.Through reinforced concrete member tests,structural stochastic finite element analysis,combined with actual bridge engineering data and Chinese engineering codes,a seismic performance evaluation method of continuous girder bridges is carried out under the framework of Performance-Based Earthquake Engineering(PBEE).The main research works and conclusions are as follows:(1)Considering the three non-linear superposition laws of deformation and energy accumulation in the damage model,the Park-Ang damage model was reconstructed.Based on the low-cycle fatigue test,the energy accumulation damage function was optimized by the application of symbol regression algorithm..This modified damage model was compared with other six modified Park-Ang damage models,which proved that the new model was used as the EDP of reinforced concrete columns with better accuracy and applicability.(2)Considering the bending,shearing and bond-slip effects of reinforced concrete columns,a standardized finite element modeling method was used to determine the parameters of the modified Park-Ang damage model.Through mixed programming of Open Sees and MATLAB,the automatic batch calculation process of model parameters and finite element simulation was realized.20 sets of static loading test and simulation data were compared,and the results show that the modeling method proposed in this paper has high accuracy.(3)Taking the reliability factor as the weight to fuse the test samples,the genetic algorithm is used to analyze the random laws of reinforced concrete members’ materials and geometric parameters.Taking the reinforced concrete column as the research object,a random finite element model was established by Monte Carlo method for static loading analysis,and compared with the experimental data.the results showed that the fitting accuracy of simulation results that considered random is 88% higher than that without considering randomness,which provided a basis for considering randomness in the finite element modeling of reinforced concrete structures(4)Taking a reinforced concrete continuous girder bridge as an example,a finite element model was established considering the randomness of the structure and seismic ground motion,and the stochastic finite element analysis was carried out by the Monte Carlo method.Based on the results of finite element analysis,using machine learning and symbolic regression fusion method,the functional relationship between composite IM and EDP of various components was established.A probabilistic seismic demand analysis(PSDA)was performed by the modified cloud-strip method,then the fragility function of the components was obtained.The results showed that the composite IM based on the machine learning and symbol regression fusion method had a 60% to 70%reduction in the logarithmic standard deviation of the fragility curve compared with the linear composite IM in the existing literature,which verified the efficiency,practicality,proficiency,and sufficiency of the method.(5)Under the research framework of Performance Based Earthquake Engineering(PBEE),and according to Chinese standards such as " Standards for Technical Condition Evaluation of Highway Bridges ",the repair measures,costs and labor consumption of 13 types of components in various damage states were summarized.Based on the component vulnerability function,the structural repair cost and repair time were calculated and analyzed by the superposition principle,and the vehicle loss and casualty were calculated by the causal relationship probability analysis method.Taking a reinforced concrete continuous girder bridge as an example,the above decision-making indicators were calculated and analyzed,the analysis results show that the repair cost and repair time were mainly concentrated on piers,abutments,concrete guardrails,and cone slopes.Although the casualties and vehicle losses were small,they could not be ignored.