Study On Prediction Model Of Vortex-Induced Vibration Of Bridge Structures

Long-span bridges are flexible structures with low damping and light weight,and they are sensitive to the vibrations caused by wind. Vortex-induced vibration is one of wind-induced vibrations which are often observed at low speed wind for long-span bridges. Vortex-induced vibration is not destructive and divergent, but it occurred at low wind speed and high frequency, and they may lead to fatigue cracks and rod damage and the amplitude is large enough to affect driving safety and comfort. Vortex-induced vibration has occurred on some bridges at home and abroad. And it has become one of the key issues in bridge wind-resistant designs. At present, study methods of vortex-induce vibrations are theory analytical model, wind tunnel test and numerical simulation.In this paper, the main study are vortex-induced vibration theoretical models, the main contents are as follows:1. This chapter reviewed the status of study on vortex-induced vibration of long-span bridges and introduced the main study methods of vortex-induced vibration of bridges.2. This chapter introduced the vortex formation, development, loss, and some vortex-induced vibration models. Then, based on the P.D'Asdia & S. Noe*model, the two-dimensional time domain vortex-induced vibrations analysis program was developed to calculate the vortex-induced vibration response of the suspended elastic cylinder with different damping ratios. The vortex-induced vibrations responses of a rectangular cross-section with the B/D is 5 (D is the height of section, B is the width of the section.) and Great belt bridge girder section model were calculated by the analysis program developed in present paper. The computational results are agree well with the literature results and the wind tunnel test results.3. This chapter introduced the near-earth wind characteristics and the turbulence effects on vortex-induced vibration, then based on P. D'Asdia & S. Noe*model builting the vortex-induced vibration analytical model under turbulence flow, and using this model to solve a elastic suspension cylinder vortex-induced vibration responses of different turbulence under sinusoidal flow .The results show that,under sinusoidal fluctuating wind, the critical wind speed of vortex-induced vibration is higher than the speed uniform flow, the lock-in range is narrower than the range under uniform flow and the vibration amplitude decreases with the turbulence intensity increases.4. This chapter introduced the main research methods of atmospheric boundary layer and numerical simulation of turbulent wind spectra, and with the simulated wind time history simulated by harmonic synthesis. The VIV responses of the elastic suspension cylinder under different turbulence winds were calculated. The results show that,the VIV occurs under low turbulence flow and the vortex-induced vibration disappeared with the turbulence intensity increases5. With Shangdi cable-stayed bridge in Beijing as an example, the VIV responses of the stay-cable with different damping ratios were calculated with the model given in chapter 2. The experimental research on vortex-induced vibration of cables was conducted through wind tunnel tests with different damping ratios. At last theoretical analysis and wind tunnel test results were compared and analyzed. The results show that the numerical results are agree well with the experimental results generally.