Vortex-induced Vibration Performance of Double-deck Steel Truss Girder During Erection
To determine the vortex-induced vibration performance of double-main-span suspension bridge with double-deck steel truss girder during stiffening girder erection,the modal analysis on structures at different erection stages were performed by using the finite element software ANSYS.The vertical bending and torsional modal characteristics varying with erection efficiency during erection were discussed.The influences of the constraints between erection girder segments and the constraints at side-span end on the bridge dynamic characteristics were analyzed.On this basis,a rigid segment model with the geometric scale ratio of 1/48.1 was made.The vortex-induced vibration performances of double-deck steel truss girder with different wind attack angles were tested by using wind tunnel tests.The lock-in wind speeds and the maximum amplitudes of bridge at different erection stages were converted.The reference limits of vortex-induced vibration amplitudes were further converted from the allowable acceleration value of 1 m/s2.The result indicates that there are strong vibration correlations among different spans.The anti-symmetric modal of single-main-span is significantly affected by the temporary constraint stiffness between girder segments.Regarding the symmetric modal of single-main-span,the participation of side-span vibration is relative high.Therefore,the linear displacement of side-span can be limited by constraining the side-span end,thus effectively suppressing the side-span vibration.The frequencies of vertical bending and torsional modals increase,but it will exacerbate the other main-span vibration.The torsional vortex-induced vibration of stiffening girder may occur during erection,but the vertical response to such vibration is not significant.The incoming flow wind attack angles obviously influence the bridge torsional vortex-induced vibration,while having minimal effect on the lock-in wind speeds.At the later erection stages,both the lock-in wind speeds and the vortex-induced vibration amplitudes increase,while the increase of torsional frequencies makes the reference limits decrease.For the erection scheme beneficial to the flutter stability of bridge,the increase of torsional frequency has an adverse effect on the vortex-induced vibration response.
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