| In recent years,relatively rare long-span wide-body flat steel box girder suspension bridge has appeared.This type of bridge brings new research topics to the wind resistance field of bridges due to its wide and flat characteristics.Therefore,in this paper,the wide-body steel box girder suspension bridge in the mountain city of Chongqing-the Cuntan Yangtze River Bridge is taken as the background.The field measurement,wind tunnel test,numerical simulation and theoretical analysis are combined and used.The wind characteristics of the bridge site,the lattice-grid generated turbulent wind field,the aerodynamic characteristics of the wide-body steel box girder,the aerostatic force coefficients,the aerodynamic admittance function,and the buffeting response law of the long-span wide-body suspension bridge in the mountainous city under the influence of multi-parameters are studied.The main contents are as follows:(1)The wind characteristics of the bridge site in a mountainous city is measured for one year.The influence of the ?tower shadow? effect of the real bridge column on the data acquisition system is studied by means of numerical analysis,and the measured results are corrected accordingly.The measured wind profile index of the bridge site is 0.166.The wind attack angle ranges from-8° to +5°.Considering the ?tower shadow? effect,the measured annual average wind speed is 3.4 m/s and the design basic wind speed is 28.1 m/s.The pulsating wind power spectrum that meets the actual conditions of the bridge site is constructed,and compared with the existing conventional pulsating wind spectrums.It is found that the low-frequency pulsating wind component of the bridge site is significant,which is more unfavorable for the buffeting response of the long-span bridge structure.The research results provide the wind load data for the buffeting response analysis of the long-span wide-body suspension bridge in the mountainous city.(2)The characteristics of two kinds of grid turbulent flow fields is studied by the combination of wind tunnel test and numerical analysis.It is found that the grid turbulent flow field does not obey the isotropic assumption within a certain distance downstream of the grid.The unstable regions of the large and small grid turbulent fields are about 4 m and 2 m,the longitudinal average turbulent intensities of the stable zone are about 7.19% and 4.60%,and the turbulent integral scales are 0.107 m and 0.073 m,respectively.The pulsating wind spectrum of the stable zone is consistent with the Karman spectrum and is not affected by the magnitude of the incoming wind speed.The results of the study determine the reasonable test position for the aerodynamic admittance experiment and provide the pulsating wind spectrum data.(3)The effects of different aspect ratios on the aerodynamic characteristics of steel box girder are studied by numerical simulation.It is found that the drag and lift aerostatic force coefficients rise with the increase of the aspect ratio.The variation law of aerostatic force coefficients of the wide-body steel box girder under the influences of different wind attack angles,different ventilation rate of sidewalk railings,different sidewalk railing positions,different overhaul track positions and different bridge surface roughness is studied through the wind tunnel test.It provides support for the experimental study of the aerodynamic admittance function of wide-body steel box girder under multi-parameter coupling.(4)Wind tunnel tests are conducted to study the influence law of the buffeting force spectrum and the aerodynamic admittance function of the wide-body steel box girder under different grid turbulent flow fields,different wind speeds,different wind attack angles,different sidewalk railing ventilation rate and locations,different overhaul track positions,and different bridge surface roughness.The practical fitting formula of the aerodynamic admittance function of the wide-body steel box girder under the influence of multi-parameters is established,which provides a powerful basis for the refined analysis of the buffeting response of the project.(5)Based on the measured wind spectrum of the bridge site in the mountainous city,the practical fitting formula of the aerodynamic admittance function under multi parameter coupling is adopted.According to the Davenport buffeting theory,with the aid of MATLAB and ANSYS analysis software,the influence of different aerodynamic admittance functions,different turbulent degrees,different wind attack angles,different sidewalk railing positions,different overhaul track positions,and different bridge surface roughness on the buffeting response law of long-span wide-body steel box girder suspension bridge in the mountainous city is studied by the time domain numerical analysis method,and compared with the buffeting response based on the standard spectrum.It is found that the lateral displacement of the buffeting obtained by the measured spectrum is 7.4% higher than that of the standard spectrum,and the torsional displacement is 12.8% higher than that of the standard spectrum.It shows that there is an error in the buffeting analysis of the long-span wide-body suspension bridge in the mountainous city to directly use the standard spectrum,and the buffeting response of the long-span bridge structure is estimated lowly.The calculation result is unsafe. |
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