Research On Buffeting And Control Of A Long-Span Highspeed Railway Continuous Beam Bridge Under Construction During Strong Wind/Typhoon

The construction of a long-span high-speed railway continuous beam bridge,which is recently erected from Yancheng to Nantong,is taken as the engineering background in this work.Combined with large-scale finite element analysis software ANSYS and CFD analysis software FLUENT,systematic research is comprehensively carried out on hotspots of the wind-induced buffeting and vibration control of the long-span high-speed railway continuous beam bridge.The research content of this paper totally involves five aspects,which are aerodynamic characteristic research of the main beam,finite element modeling and dynamic characteristics analysis of the bridge,simplified simulation of a 3D fluctuating wind field,buffeting analysis in time domain and its vibration control study at the cantilever state,respectively.The main research contents include as follows:(1)Research on aerodynamic characteristics of the long-span high-speed railway continuous beam bridge based on CFD.The whole study is conducted based on the computational fluid dynamics(CFD)method.Firstly static tri-component coefficients and flutter derivatives of a thin flat plate are identified to verify the accuracy of the simulation models,meshes and calculated boundary conditions.Then similarly the SST k-ω turbulence model is used to simulate the two-dimensional flow field of the typical beam sections of the long-span high-speed railway bridge at the wind attack angles of-3°,0°and +3°,so as to obtain the static tri-component coefficients and eight flutter derivatives of the typical sections.Combined with the characteristics of the 2D flow field,the wind pressure and velocity distributions at the various sections under different wind attack angles are thoroughly analyzed.The identified aerodynamic parameters and characteristics of the railway bridge can be utilized for the following buffeting analysis for lack of the wind tunnel test.(2)Finite element model establishment of the long-span high-speed railway continuous beam bridge and its dynamic characteristic analysis.According to the main structural design parameters of the high-speed railway bridge,the overall structure is separated into three parts,which are the main girder system,the pier system,and the support system,thus a threedimensional finite element(FE)of the high-speed railway bridge at the bridged and maximum cantilever state are separately established in ANSYS.The first 200 order modal parameters of the bridge are obtained with the Block Lanczos method,and a more in-depth analysis of the first 20 order modals are conducted on the two models.Comparison of the typical modals between MIDAS and ANSYS is also carried out.The results can provide an accurate finite element model for the subsequent buffeting response analysis.(3)Buffeting analysis in time domain of the maximum cantilever state of the long-span high-speed railway continuous beam bridge during construction.According to the structural features and dynamic characteristics of the bridge,and considering the correlative natural wind characteristics at the bridge site,a normative spectrum is used as the target spectrum to simulate the three-dimensional fluctuating wind field of the bridge accordingly.On this basis,the wind load acting on the bridge is divided as static wind loads and buffeting forces to conduct buffeting analysis in time domain based on the Davenport quasi-steady theory.The buffeting performances of the main girder are then analyzed in depth,and the effects of different design wind speeds and attack angles of the buffeting performances at the cantilever end of the longspan high-speed railway bridge are thoroughly discussed during construction.(4)Comparative study on the vibration control of the long-span high-speed railway continuous beam bridge under strong wind/typhoon under construction.Based on the two control measures,which are wind resistance cable and temporary pier,the study on buffeting mitigation of the long-span high-speed railway bridge is carried out.The control efficiency is evaluated from the perspectives of displacement response,acceleration response and body comfort.A comparative study on the buffeting performance of the long-span high-speed railway bridge with different layout schemes of the wind resistance cables(changing its cross-section size,layout type,initial stress,angle with horizontal direction,etc.)is further conducted.Also the effect of different locations of the temporary pier on the buffeting vibration control is thoroughly discussed.Finally the proposal of a reasonable scheme for the buffeting vibration control of the long-span high-speed railway continuous beam bridge is tabled accordingly under strong wind/typhoon during construction.