| With the rapid development of bridge construction technology in China,the record of long-span bridges is constantly refreshed,and the bridges become more flexible,the more likely it is to cause the vortex-induced vibration(VIV)problem.For example,the vortical-induced resonance problem of Xihoumen Bridge,Yingwuzhou Bridge and Humen Bridge has aroused great concern.In conventional bridge wind resistance research,the VIV characteristics are mainly carried out in the uniform wind field through the segment model,and the wind in nature is distributed in turbulent state.How to consider the turbulence effect of vortex vibration on bridges has become one of the most necessary topics in the research on wind resistance of long-span bridges.In view of this,this paper studies the VIV response and vortex-induced force(VIF)characteristics through elastic suspension wind tunnel tests of segment models in different turbulence field.Combined with ANSYS three-dimensional elastic finite element model,the distribution characteristics of VIF and its influence on VIV are analyzed.The main contents and results are as follows:(1)A three-section pressure measurement model with a height-width ratio of 1:6 rectangular section is used to test the vortex-oscillation interval,VIF time history and pressure signals at different turbulence levels by elastic suspension wind tunnel test.Based on the results of pressure test,the variation trend and influencing factors of dynamic lift spread correlation are discussed.The results show that the dynamic lift is not completely correlated along the spanwise direction in the vertical vortexes of the rectangular model,the spanwise correlation is negatively correlated with the turbulence degree,and the spanwise correlation in the rising section of the vortexoscillation interval is higher than that at the maximum amplitude.(2)Based on Scanlan’s empirical nonlinear model "Attenuation from amplitude A0 to resonance",the parameters of VIFs in two intervals of 1:6 rectangular uniform field and that in the vortex-induced regions of 3.04% turbulence were identified.The vortex-induced time history obtained by fitting is compared with that obtained by balance measurement.It is found that the amplitude fitted by Scanlan method is basically the same as that obtained by balance test,but there is a phase difference that cannot be ignored.(3)The influence of turbulence on vortex vibration was tested by streamline box girder segment model test.The results show that the vortex-induced performance of the negative incidence is better than that of the positive incidence.When the turbulence increases to 3.04%,the vortex amplitude increases by 8.87% compared with that under the uniform field,and the vortex interval is advanced.However,when the turbulence continues to increase to 5.98%,the amplitude decreases obviously.It shows that,to a certain extent,increasing the turbulence of the box girder model can promote the vortex vibration and further increase of turbulence will restrain vortex vibration.(4)Based on ANSYS calculation software,the eddy vibration response of 1:6 rectangular section with three turbulences is calculated and analyzed by full-method transient analysis.First,a single-degree-of-freedom spring oscillator model is used to simulate the sectional model,and the calculation results are very close to the test values.The finite element model of simply supported beam with scale ratio of 1:1 of segment model is established,and the eddy excitation force is applied to the simply supported beam according to the spread distribution fitting function.After correcting the influence of vibration mode,the finite element calculation results of the three wind fields are compared with the measured values.It is found that except for individual points,the error is large but basically consistent with the measured results. |
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