Wind-induced Damage Risk Analysis Of Large Span Highway Cable-stayed Bridges

Although the research on wind resistance theory of bridges has been well established,there are still some shortcomings in the risk assessment of wind-induced damage for large span cable-stayed bridges.Generally,deterministic analysis is used to obtain the critical wind velocity or the maximum value of the response and compare it with the allowable value for wind performance assessment,but from the perspective of considering the parameter uncertainty and risk analysis based on the reliability theory,the wind performance assessment of large span cable-stayed bridges is relatively late,and the theoretical system and assessment method of bridge wind resistance risk need to be further improved.For large span bridges,wind is the main factor leading to disaster risk,Among them,wind-induced damage vibration(static wind instability,flutter instability)is particularly important because once it occurs,it will cause irreversible effects on the bridge.Wind-related disasters bring huge risk pressure to the bridge managers and also lay the risk potential for bridge users.Therefore,wind vibration reliability analysis and wind risk probability study should be carried out for large span cable-stayed bridges during operation,and wind damage vibration risk should be evaluated in time to avoid the occurrence of bridge structural instability events as much as possible.In this thesis,the Ningbo Xiangshan Port Bridge is used as the engineering background for analysis,and the study mainly includes the following aspects.(1)Analysis of structural dynamic characteristics of Xiangshan Port Bridge.The finite element model of Xiangshan Port Bridge is established by using ASNYS parametric design language,and modal analysis is carried out,which lays a foundation for static wind instability and flutter analysis.(2)Analysis of the aerodynamic characteristics of the Xiangshan Port Bridge.ICEM software was used to establish the geometric model of the main girder,and the method of regional grid division was used to establish the grid model.After that,the simulation calculation of the static three-part force coefficient of the main girder section was carried out in Fluent software,and the forced vibration method was used to extract the values of the flutter derivatives of the main girder to obtain the static three-part force coefficient and flutter derivatives of the main girder.(3)The static wind instability analysis of Xiangshan Port Bridge was carried out,and the effects of parameters such as initial wind angle of attack,wire breakage rate of the cable and cable breakage position on the static wind stability of the large-span cable-stayed bridge were investigated separately,so as to obtain the influence rule of each parameter to the static wind instability,and the most influential and unfavorable cases from these parameters were selected for the static wind reliability analysis of the bridge.(4)Wind-induced flutter time history analysis of Xiangshan Port Bridge.Firstly,the ideal flat plate simply supported beam model is used to prove the accuracy of the flutter time history analysis method in ANSYS,and then the influence of parameters such as main girder stiffness,damping ratio,cable break rate and cable break position on the flutter stability of large span cable-stayed bridge is explored separately to obtain the influence rule of each parameter flutter,which provides reference and basis for the flutter reliability analysis of large span cable-stayed bridge.(5)Establish and improve the wind-induced damage risk analysis method,introduce the reliability into the risk analysis,analyze the risk of static wind instability and the risk of flutter instability respectively,then quantify the risk loss by using the ratio of project cost and service life,and get the corresponding risk level under each case,and finally elaborate the response strategy for the wind-induced risk.