Wind Characteristics At Bridge Site Over Mountainous Terrain And Wind-induced Vibration Of A Long-span Bridge With High Piers

With the rapid development of China’s economy,the construction of traffic facilities enters a new stage of development and the focus of transportation infrastructure construction is projects across mountain valleys and across bays at present and in near future.In order to adapt to the mountainous terrain,the long-span bridges with high piers become the first choice for mountain bridges.Wind characteristics over mountainous terrains,wind load and wind-induced vibration are one of the key issues affecting the wind-resistant design of long-span bridges in mountainous areas.Based on the Xiangjiang Bridge on the new Wengma Railway in Guizhou,the researches on the reasonable transition section of the terrain model,the wind-induced vibration during the construction stage of long-span bridges with high piers,and the wind barrier selection of long-span bridges with high piers in the mountain area were carried out.The specific research contents are as follows:(1)Computational Fluid Dynamics(CFD)simulation was adopted to calculate the two-dimensional wind fields of combinations of Witozinsky curves with different virtual inclination angles and horizontal lines.Four factors including the increase ratio factors of wind speed,average wind attack angles of different curves,increase ratio factors of longitudinal turbulence intensity and vertical turbulence intensity were analyzed comprehensively by weight solution based on the correlation degree to determine the reasonable transition section form on the edge of the terrain model.(2)Based on the Xiangjiang Bridge on the newly-built Wengma Railway,fabricate a wind tunnel test model with the center of the bridge mid-span with a geometric scale ratio of 1: 1500 and the simulation range of the terrain model is R=4000m.The three-dimensional transition sections were made according to the optimal transition section form.The transverse wind speed,wind attack angles at bridge deck level,the wind profiles at different locations and the turbulence intensity profiles with and without transition sections were compared through winf tunnel tests.(3)The three-dimensional numerical simulation was used to simulate the wind fields with and without transition sections and the numerical results were compared with these of the wind tunnel test.Then,further evaluation and comparison of the effect of the transition section on the accurate simulation of the average wind characteristics at the bridge site were conducted through the flow field visualization.(4)An aeroelastic model of the Xiangjiang Bridge in the maximum double cantilever stage was designed and fabricated.On the tapered pier,pressure measuring holes were set in measurring sections at different heights away from the ground.The variations of the force coefficients and surface pressure coefficient distribution of the high pier in uniform flow and turbulent flow fields were studied.By analysing data obtained from the pressure measuring process,the variations of force coefficients and surface pressure coefficient distribution with wind speed and height were obtained in uniform flow and turbulent flow fields.The Root Mean Square(RMS)values of the force coeeficients in axial direction were calculated to provide reference for accurate time-domain buffeting analysis.(5)Wind tunnel test and numerical simulation were adopted to conduct the aerodynamic optimization of wind barriers on the long-span bridges with high piers in mountainous areas.The wind reduction effect and aerodynamic force coefficients of bridge section model under different wind attack angles of eight wind berriers with different forms and porosities was studied.Then,weight solution based on the correlation degree was adopted to assess the wind reduction effect and aerodynamic force coefficients,determining the optimal wind barrier form under large wind attack angle.