Reinforced CFST Arch Bridge Finite Element Model Updating And Evaluation Of Ultimate Bearing Capacity Of Arch Rib

Concrete-filled steel tube(CFST)arch bridge has been widely adopted in China due to its excellent mechanical performance,high economic benefits and beautiful shape.Its construction technology has always been in the lead.However,bridges inevitably suffer from the aging of materials,environmental erosion and various human factors,resulting in different degrees of damage in different parts.There is an emerging method to reinforce old long-span arch bridges by replacing bridge deck system,However,there is no systematic research on the impact of continuous loading and unloading process on CFST arch ribs in the short term.The method of evaluating structural bearing capacity by load test and non-detective testing also has its limitation.This thesis improves the particle swarm optimization(PSO)and differential evolution(DE),modifies the finite element model of the arch bridge based on the improved hybrid optimization algorithm,and evaluates the loading limit of the strengthened arch ribs based on the modified model.The main contents of this thesis are as follows:(1)This thesis proposes an optimized hybrid algorithm of PSO and DE(PSO-DE)for the problems that particle swarm optimization(PSO)and differential evolution(DE)algorithm are easy to fall into local optimum and the convergence speed is slow.The performance of this algorithm is tested by Ackley function,and the result shows that the improved PSO-DE has outstanding performance in convergence and global optimization.(2)This thesis uses PSO-DE and the first-order optimization algorithm built in ANSYS to modify the finite element model of single arch rib,analyzes the results by contrast,and finally verifies the feasibility and superiority of the improved model updating method.The result shows that this method has good stability and higher accuracy.In addition,the author writes a statement that makes the responses of ANSYS can be called automatically and circularly by MATLAB.The problem of slow data interaction between ANSYS and MATLAB is solved,thus greatly improves the efficiency of model updating.(3)This thesis analyzes the sensitivity of the design parameters through the initial finite element model of arch bridge made by ANSYS,and modifies the structural finite element model by PSO-DE based on the static response of the reinforcement and reconstruction project of Liujing-Yujiang Bridge.To verify the accuracy and static performance of the modified model,this thesis compares the measured value from the load test of the new bridge with the calculated value of the Midas model and the modified model.The result shows that the modified model has higher computational accuracy.It can reflect the actual static performance and provide theoretical guidance for safety assessment and health monitoring of this bridge.(4)This thesis makes material non-linearity analysis of CFST arch ribs based on the modified finite element model,and sets a loading combination from the bridge design specifications as a standard to load the L/2 and L/4 sections step by step.At last,this thesis evaluates the bearing capacity limit of CFST arch ribs strengthened by bridge deck replacement method on the grounds of the calculation.