Experimental Study On The Spanwise Correlation Effects Of Vortex-induced Vibration Of Large Span Bridge Girder

Large-span bridge girder with relatively light quality, small vibration frequency,low damping can happen vortex-induced vibration(VIV) easily during its operation period at commonly encountered wind speed, that causes the problems of riding comfort and the structural fatigue life. The main girder structure actually has three-dimensional characteristics, affected by the actual wind field and the mode of vibration, the vortex-induced forces(VIFs) along the spanwise girder are not incompletely correlated, the research of the spanwise correlation of VIFs is one of the main aspects of the study of VIV. This paper is funded by the project of "Experimental study on spanwise of vortex-induced-forces of main deck with long-span bridge section"(NSFC, Number: 51178181). Taking the Guangdong Jiangshun Bridge as the project background, the study on the spanwise correlation effects of VIV of large span bridge girder has been carried out. The main research work of this paper is as follows:(1)The typical cases of vortex-induced vibration and the control measures of long-span bridges are briefly introduced. The research status of VIV is summarized.The research content and route of this paper are put forward.(2)The Jiangshun Bridge 1:80 ratio section model was designed and made. With the way of simultaneous measurement of vibration and pressure wind tunnel tests of the model were conducted to identify lock-in regions of different wind attack angles and to study the spanwise correlation of VIFs and identification of aerodynamic VIFs parameters. The research results show that the spanwise correlation coefficients in VIV state are larger than that in stationary state and the spanwise correlation is mainly influenced by self excitation forces and forced forces.(3)Combining with the dynamic mesh and sliding mesh techniques, the CFD simulations of VIV of the rectangular cylinder with aspect ratio 5 and the streamlined closed box girder section of the Jiangshun Bridge were conducted, and the mechanism of VIV has been preliminarily analyzed. On this basis, the method based on CFD numerical simulation method for the identification of the vortex-induced forces parameters of the bridge girder was proposed. It is verified that the method is feasible by comparing with the experimental identification results.(4)The Jiangshun Bridge 1:80 ratio taut strip model was designed and made,wind tunnel tests with the way of simultaneous measurement of vibration and pressurewere conducted. Compared the taut strip model’s wind tunnel tests results with the section model’s, the research results show that the spanwise correlation of VIFs of the bridge girder is mainly influenced by vibration mode in VIV state.(5)The FEM method for calculation of VIV of the bridge girder based on Scanlan empirical linear model has been preliminarily proposed. The VIV time history response of the section model and the taut strip model were calculated by the FEM method. The research results show that the calculation results of FEM are agree well with the experimental results.