| With the rapid development of economy and the need of perfect road network,expressways gradually enter mountainous areas.Due to the influence of unfavorable terrain such as mountains,valleys and rivers,large-span continuous steel bridge has been applied more and more because of its light weight and low construction difficulty.With the gradual growth of traffic volume,the design of upstream and downstream separation is often adopted.Due to the small space between main beams of double-span bridge deck,the upstream and downstream Bridges will influence each other under the action of incoming wind.Different from the wind-induced response of single-amplitude bridge,the aerodynamic interference effect will cause the problems of vortex vibration,flutter and chattering,which can’t be ignored.Nowadays,it has become one of the most important problems in wind-resistant design of double-amplitude bridge.In this paper,the aerodynamic interference effect of the double-width steel box girder and the mechanism of the vortex vibration performance of the double-width steel box girder under different spacing are studied by the segmental model test,the full-bridge air-elastic model test and the numerical simulation calculation.The main work is as follow:1.Based on the engineering background of parallel double-width blunt steel box girder bridge with variable section,the vortex vibration performance of double-width steel box girder is studied through wind tunnel test and reasonable aerodynamic optimization measures are proposed.The vortex induced vibration(VIV)displacement response time histories of the main girder at different attack angles were measured by 1:40 scale segmental model wind tunnel test;Under the most unfavorable angle of attack,the influence of the spacing between two box girders on the VIV performance of the main girder is studied,and the influence of the railing closure form and ventilation rate on the VIV performance is further tested on the basis of changing the spacing.Through the wind tunnel test,the VIV displacement response of the model and the pressure time-history data of each measuring point on the surface were obtained.Taking a working condition every 0.5m,the mean value and standard deviation mean square error of the fluctuating pressure coefficient of the measuring points on the box girder surface with an spacing of 0.5m to 3m,as well as the correlation and contribution coefficient of local aerodynamic force and overall aerodynamic force are compared and analyzed.2.According to the results of dynamic characteristics and based on the similarity of parameters,the full bridge aerodynamic model of the variable section double width steel box girder is designed and manufactured.The mass,stiffness,modal frequency and damping of each component are verified,and the aerodynamic model of the whole bridge is determined to meet the test requirements.In a uniform flow field,a validation test is carried out on a single girder,and then the influence of spacing on the aerodynamic interference effect of a double-width steel box girder with variable cross-section is investigated.3.The 2D main beam section model is established in the pre-processing software.The model was calculated based on Fluent,and the UDF calculation program was embedded in the transient state to analyze the vortex-vibration performance of the main beam section.Finally,the results of numerical simulation were compared with the results of eddy vibration amplitude of 2d segmental model wind tunnel test,which confirmed the accuracy of the numerical calculation method,and further explored the influence mechanism of aerodynamic interference effect of double-amplitude steel box girder. |
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