Research On Aerodynamic Interference Effects Of Main Girders Of The Parallel Long-Span Highway And Railway Bridges

As China has reached a new stage of development,the construction of transportation infrastructure has enterd a new historical developmen t stage.In order to solve the problem of increase of traffic volume,some large-span bridges with double-decks or separate parallel decks were built generally.However,the aerodynamic interference effects of the two adjacent bridges or the bridge with parallel decks cannot be ignored because of the small distance between the parallel girder sections.Based on the Quanzhou Bay Sea-Crossing Bridge of the Fuxia High-speed Railway(Railway Bridge)and Quanzhou Bay Sea-Crossing Bridge of the Quanzhou highway around city(Highway Bridge),the aerodynamic interference effects on the parallel large-span highway and railway bridges with three decks are studied,which include the static wind load,characteristic of vortex-induced vibration and flutter stability.The main contents of this research are as follows:(1)Firstly,the situation of the existing and under-construction large-span bridges with parallel decks are summarized.Then,the state-of-the-art on the study of aerodynamic interference effects of circular and square cylinders,high-rise buildings,and the large-span bridges with parallel decks were reviewed.Finally,the main ideas of the present thesis are proposed.Based on the Railway Bridge,the rigid segment main girder model with a length scale of 1:60 was designed and fabricated,respectively.Furthermore,the experimental setup was designed to conviencely change the horiozontal net distance between the railway bridge deck a nd highway bridge decks.The following factors,namely the horizontal net distance D/B(D is the net distance between the railway bridge deck and the windward deck of the highway bridge,and B is the width of the railway bridge deck),the vertical distance L/H(L is the vertical distance between the geometry center of railway bridge deck and geometry center of the highway bridge decks,and H is the height of the railway bridge deck),wind attack angle,and the damping ratios,are considered in this study.(2)The aerostatic coefficients of the railway bridge girder section under the aerodynamic interference effects on the parallel large-span highway and railway bridge girder sections with three decks are studied by wind tunnel test and numerical simulation,respectively.The following factors,namely the horizontal net distance D/B and the vertical distance L/H are considered.(3)The aerodynamic interference effects on vortex-induced vibration(VIV)of the parallel long-span highway and railway bridge girder sections with three decks are studied by wind tunnel test.The following factors,namely the horizontal net distance D/B and the vertical distance L/H,wind attack angle and damping ratio,are considered.(4)The mechanism of the VIV of the railway bridge girder section are studied by wind tunnel test and numerical simulation,respectively.According to the mean and fluctuating pressure coefficient,lift spectrum analysis obtained from the wind tunnel test and static instantaneous vorticity obtained from the numerical simulation,the mechanism of the VIV of the single railway bridge girder section and the railway bridge girder section under the aerodynamic interference effects are investigated.(5)The flutter stability of the single railway bridge girder section,highway bridge girder sections with double decks,and the parallel highway and railway bridge girder sections with three decks are studied,respectively.The following factors,namely the horizontal net distance D/B and the vertical distance L/H,wind attack angle and damping ratio are considered.