The Vortex-induced Vibration And Vortex-induced Forces Spanwise Correlation Research Of Typical Cross Section

Long-span bridges have many natural modes, and each of these modes may beselectively excited by vortex shedding at different wind velocities. Therefore,investigation on the vortex-induced vibration (VIV) velocity and vibration amplitudefor each mode is crucial for pratical purpose. There have been many investigations onVIV of rectangular and H-shaped section. However, the study on the variation of VIVmaximum amplitude with the change of modal frequency, mass parameter andaerodynamic damping is insufficient. Scruton number is an important factor that willaffect the VIV locking range and vibration amplitude. But the mass parameters anddamping parameters have different influence on VIV. It is lack of the relationshipbetween Scruton number and VIV. On the other hand, in the action of actual wind, thevortex-induced forces along the axis direction of the bridge are not completelycorrelated. The correlation of vortex-induced forces (VIFs) is especially remarkablefor long-span bridges. The study of spanwise correlation has important significancefor VIV amplitude prediction. Based on the above questions, this paper mainly studiesthe following aspects:(1)The main bridge wind-induced vibration type is introduced, and a review ofexperimental and theoretical investigation concerning the VIV of bridge deck ispresented.(2)Two different sizes of rectangular section model test and H-shape sectionmodel are tested in smooth flow. The results show that rectangular section andH-shaped section vertical VIV amplitude are independent of the frequency for themodel with the same mass and structure damping.(3)The influence of mass parameter and damping parameter on VIV amplitude ofrectangular section and H-shape section are studied. It is shows that these twosections VIV amplitude decrease significantly with the increase of the structuraldamping. But the VIV amplitude is notquite very sensitive to the change of massparameter under same structural damping. Sectional flutter derivatives are used toanalyze the aerodynamic damping under different mass. It is shown that the dampingratio caused by aerodynamic damping decreases with mass parameter, which mayexplain the insensitivity of VIV amplitude to mass parameter.(4)Rectangular section model wind tunnel test is observed to have two VIV locking range and the maximum amplitude ratio of these two locking range is about2.2. The aerodynamic damping of these two VIV locking range is determined based onflutter derivatives, and the the maximum amplitude ratio obtained with harmonicvortex-induced force model considering the influence of aerodynamic damping isshown to be consistent to experimental results. It is found that the aerodynamicdamping differences lead to maximum amplitude ratio not inversely proportional withSt2.(5)The numerical simulation of VIV is conducted based on the rectangularsection and H-shape section wind tunnel test results. It shows that numericalsimulation results agree well with the wind tunnel test.(6)By cylinder sectional model test, the spanwise correlation of vortex-inducedforce is analyzed. The results show that the spanwise correlation on the90°location islarger than180°location in the different section. The vortex-induced force correlationis related to amplitude and Reynolds number.