| With the rapid development of long-span steel bridges, how to decrease andprevent the Vortex-Induced Vibration (VIV) of these bridges has turned into one ofthe key problems on Wind-resistant design of bridges with large span.As the researchfocusfor of wind-resistant design of long-span bridges,the VIV of main deck withbridge section is mostly conducted by section model tests in wind tunnel,while thetheoretical analysis based on2D and theories of3D are almost a blank. Theexperimental investigations on VIV and spanwise correlation effecs of vortex-inducedforces (VIFs) were conducted in present thesiscombining the research project of"Experimental study on spanwise correlation of vortex-induced-forces of main deckwith long-span bridge section "(NSFC, Fund Number:51178181). A taut strip modelof the aspect ratio5:1rectangular cylinder was designed and tested under twodifferent damping ratio conditions with the purpose to study the phenomena ofmulti-mode VIV and spanwise correlation of VIFs.Finally based on the results of thetaut strip model test, the amplitude estimation formula of VIV in EuroCode wasanalyzed. This work mainly includes the followings:(1) Based on the brief review the state-of-the-art of VIV, spanwise correlation ofVIFs and multi-mode VIV of long-span bridges, consindering the spanwisecorrelatons of VIFs and modeshape effects on VIV, a taut strip model was designed toinvestigate the three-dimensional effects on VIV of bridge structures. Finaly, the mainresearch contents and technical route were presented.(2)The basic concept and influence factors of spanwise correlation of VIFs wereintroduced. The experimental data of the test of spanwise correlatiron of VIFs therectangular cylinder with aspect raio of5to1was processed and analyzed. The VIFsof the rectangular cylinder was calculated based on the pressure data of therectangular cylinder model, and the dynamic responses of VIV of the rectangularcylinder were calculated. The numerical results of VIV of the rectangular cylinderbased pressure data are agree well with the experimental results.(3) The taut strip model of the5:1rectangular cylinder was designed based onthe principles of the taut strip model. The dynamic characteristic parameters of thetaut strip mode were given in present thesis. Two different conditions were designedconsidered whether the rectangular section contained pressure tubes or not. Theexperimental results of the taut strip model test were analyzed systematically. The experimental results of the amplitudes for different mode were compared with thecalculated resultes which werecalculated with the formula of VIV given byEuroCode. A modify method was introduced to take into account the mode shapeeffects on the spanwise correlation of VIFs structures based on results of spanwisecorrelation of VIFs of rigid sectional model. The modify method was validated by theexperimental dada of the taut strip model. Finally, the spanwise correlation of VIFs ofthe stationary and oscillating taut strip model were calculated separately.(4)Inorder to identify areodynamic parameters with from stationary toresonance response curves which were obtained from taut strip model test,the generalequation solution with resonance response of the model under harmonic loads werededuced. The parameter identification methods for two kinds of VIF models, namelythe liner empiric model aof nonlinear empiric model given by Scanlan, were given.The areodynamic parameters of VIFs were identified based on the experimentalresults of the taut strip model. |
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