Study On Performance Optimization And Mechanism Of Vortex-Induced Vibration Of Long-Span Suspension Bridge With Steel Box Girder

Long-span bridges are characterized by low damping,softening and low natural vibration frequency.However,the auxiliary components existing in the actual bridge deck also make it have typical blunt body characteristics,so the vortex-induced vibration of main girder is prone to occur frequently under the low wind speed,which will seriously affect the use of performance of main girder and the traffic safety.Aiming at the above problems,in this paper,the typical closed steel box girder section which is widely used in practical engineering construction is taken as the research object,so the vortex-induced vibration performance of main girder section and vibration suppression mechanism of corresponding aerodynamic measures were studied through numerical simulation and wind tunnel test of synchronal vibration and pressure measurement with large scale sectional model.The main content of this paper show as follows:(1)The typical cases of vortex-induced vibration of long-span bridges are briefly summarized,and analyzed the research status and main research methods of vortex-induced vibration and spanwise correlation of vortex-induced force of a long-span bridges.Finally,the research significance and main contents of this paper are proposed based on the overview above.(2)Aiming at the closed steel box girder section of long span suspension bridge,a sectional model with scale of 1:25 was designed to study the vortex-induced vibration behavior of the main girder under different wind attack angles through wind tunnel test of synchronal vibration and pressure measurement,and combined with previous relevant research results,the vibration suppression measures for the bridge are proposed based on the above research results.(3)Based on the vortex-induced vibration response results of the original design section of the main girder,representative wind velocity points were selected in the torsional vortex vibration lock-in region to study the aerodynamic time-frequency evolution characteristics of the main girder section during the whole vortex-induced vibration generation process.(4)Based on the original design scheme of the main girder,the height of the railing cornerstone and its position on the bridge section were changed through wind tunnel test of pressure measurement and numerical simulation,so as to study the influence mechanismof the railing cornerstone on the vortex-induced vibration characteristics of the main girder section of the bridge.(5)The influences of spanwise distance and vortex-vibration amplitude on spanwise correlation of vortex-excitation force at the main girder section and pressure at the measuring point are studied in time domain and frequency domain respectively based on the same step vibration pressure wind tunnel test.