Study On Fatigue Of Bridge Components Caused By The Torsional Vortex-induced Vibration

Because of the frequent occurrence of low wind speed at bridge site, bridge components may suffer from frequent vortex-induced vibration, which may result in serious fatigue damage of components or even bridge collapse. Bridge engineering practice shows that the fatigue failure of steel suspenders is one of the leading damage to steel arch bridges. Base on reported wind-induced fatigue and wind tunnel tests for a steel arch bridge, this paper attempted to, carry out fatigue research on a slender H-shaped suspender with web slots, including the following aspects:(1) The damage caused by wind-induced vibration of bridges was introduced, and the reasons that vortex-induced vibration caused fatigue damage of steel bridges was analyzed, suggesting that the problem of vortex-induced vibration causing fatigue was long-standing. It is necessary to study the steel bridge fatigue causing by vortex-induced vibration.(2) Based on wind tunnel testing of a section model, this paper studied vortex-induced vibration characteristics about a stiffening girder section model from Wu Jiang bridge in smooth flow to obtain the vortex vibration characteristics about the stiffening girder in large wind attack angle and the system damping changed on the vortex-induced vibration impact; the H-shaped suspender sectional mode of Dong Ping bridge was studied to obtain vibration characteristics and response in range of wind attack angle of 360°range. It provided a basis for fatigue study of the suspender.(3) The characteristics of vortex-induced force about the current model was comprehensive analyzed, and combining with wind tunnel test data. Aerodynamic parameters was identified based on the Scanlan empirical linear model, suggesting that the aerodynamic force being excited by the structure movement governing the system vibration, while the force caused by vortex shedding was secondary.(4) Based on the principle of the P.D'Asdia numerical model and the boundary layer flow theory, the P.D'Asdia numerical model was extended to the calculation of torsional vortex-induced vibration, with vortex-induced vibration test data about the suspender section model. It is found that the model was reasonable to simulating torsional vibration in the wind attack angle less than 5°, while it should be improved when the wind attack angle was greater than 5°. (5) Using vortex-induced vibration of the suspender sectional model, torsional vibration of the real bridge under various wind attack angle was obtained. With the fatigue analysis methods in the U.S. AASHTO specification, torsional fatigue life of vortex-induced vibration was reasonable estimated, and the fatigue strength and category of the H-shaped suspender were presented.