Research On Damage Identification Method Of Cable-stayed Bridge Based On Power Spectrum Sensitivity Analysis

The health status of Bridges is affected by complex and changeable environment and aging of materials,which seriously threatens the safety of people’s lives and national property.At present,there are still limitations in damage identification for large Bridges.It is of great research significance and engineering application value to develop an efficient structural damage identification method and apply it to actual bridge engineering.In this paper,the cablestayed bridge structure is taken as the research object,and a cable damage identification method based on response power spectrum and sensitivity analysis is proposed.The main research work is as follows:(1)According to the structure form of the cable-stayed bridge and the nonlinear problem of the structure,the finite element model is established.Transient analysis method is used to obtain the structural response under vehicle load,and then the corresponding power spectrum is obtained.(2)Considering the redistribution of internal forces in the cable-stayed bridge system caused by cable damage,the damage parameters were determined.When a cable is damaged,the stress system of the structure becomes unbalanced,which leads to the change of the internal force of the whole cable system to reach a new equilibrium state.Based on this phenomenon,the axial strain matrix of all cables in the cable-stayed bridge system is constituted as the damage parameter.(3)Based on the sensitivity analysis method,the damage identification method based on the combination of response power spectrum and sensitivity analysis is studied.Aiming at the power spectrum,it was solved from the aspects of structural dynamics and signal processing.Combined with the sensitivity analysis method,the sensitivity equation based on the response power spectrum to the damage parameters was established.The finite difference method was used to solve the equation and get the damage parameters,so as to realize the damage identification of the stayed cable.Taking the finite element model of cable-stayed bridge as the research object,the damage identification of single cable damage condition and combined damage condition is carried out.The results show that this method can accurately identify the damage location of the cable,and basically determine the degree of the damage.(4)To solve the power spectral sensitivity equation,a set of program is designed to realize the interaction design with the finite element analysis software.Solving the sensitivity equation is an iterative process,and each iteration requires redefining the axial strain parameters of the cable system and recalculating the power spectrum sensitivity equation.Therefore,a set of program is designed and developed to realize the iterative process of equation solving by using the method of program call and data transmission,which improves the calculation efficiency.(5)Based on the actual project of Baoding Juli Bridge,the finite element model is established,and the model is modified through the bridge cable force and modal experiments.The influence of cable damage on the power spectrum of structural response is analyzed,which further demonstrates the effectiveness of the proposed response power spectrum in the application of damage identification of cable-stayed bridge structures.