Study On Vibration Of Wind-Vehicle-Bridge System Of Suspension Bridge With Wide-body Flat Steel Box Girder In West Valley Area

With the rapid development of highway bridge construction, more and more long-span suspension bridges in the west valley area turned up. With the increasing of main girder's width, wide-body flat steel box girder has appeared. This paper took Chongqing Yangtze river bridge as the engineering background. The wind environment of bridge site in characteristics and parameters, the buffeting response of bridge under the west mountain wind, influence of cross wind wide-body flat steel box girder aerodynamic performance, and the wind-vehicle-bridge system vibration were studied by the field measurement, wind tunnel test, theoretical analysis and numerical computation method. The main research content as follows:(1) The wind speed and direction of modified observation system was built in the beach of Yangzi river at the bridge site, wind speed and wind direction's change with height were studied. It was found that local microclimate characteristic of the bridge was evident, and the main wind direction was changed with increasing of height. Wind profile index, turbulence integral scale and turbulence spectrum were compared with the standard. Turbulence intensity offset to low frequency in horizontal direction and offset to high frequency in vertical at the bridge site. Fluctuating wind power spectrum conforming to the bridge site was put forward.(2) Buffeting response of the bridge was obvious. Wind attack angle influences on horizontal and vertical displacement greatly. Horizontal displacement of the main tower increases greatly with the wind speed. This bridge should pay special attention to buffeting response caused by fatigue damage in the design and operation. Analysis of buffeting response laid the foundation for wind-vehicle-bridge system vibration's calculating.(3) Bridge deck roughness function was proposed with the application of the random harmonic function. The new function's stable zero mean Gaussian distribution was proved in theory and numerical simulation. The power spectral density was compared with standard spectral density, correctness and feasibility of the new function was proved. The good randomness of generated surface roughness was compared with others.(4) Basing on wide-body flat steel box girder section model wind tunnel test, wind speed, the rail leak rate, bridge deck roughness, large angle of attack, distance between vehicles and vehicle number's influence on aerodynamic performance of the main girder were studied. From the flow field characteristics around, the reason and mechanism were explored. Research results showed that the wide-body flat steel box girder under different wind speed in the static coefficient of three component value was very close, and effect of Reynolds number was small, while the aerodynamic performance was good. Rail leak rate and the change of bridge deck roughness on the static three coefficient component had a big influence. When angle wind attack and bridge deck roughness changed, the torsional response of the main girder was more sensitive. Girder under large angle wind attack was prone to a wide range of large amplitude vibration of vortex. The greater of bridge deck roughness, the smaller vortex vibration response. Vortex vibration response was greater without vehicle than with vehicle on the girder. With the decrease of the vehicle distance, the vortex vibration response increased gradually.(5) Through the vehicle vibration differential equation under the action of the lateral wind,the wind-vehicle-road vibration system was analyzed. The response of the vehicle under different wind speed and vehicle speed were studied under the lateral wind, pulsating wind to analyze the wind-vehicle-bridge vibration system and the vehicle speed under different weather conditions can provide a basis to the traffic rules. By Baker accident model and the programming, the road safety traffic was calculated, driving safety speed was given.(6) According to the vehicle-bridge system vibration equation, the program of vehicle-bridge vibration system was verified and the correctness of it was proved. The system was analyzed under the different vehicle speed, vehicle spacing and bridge deck roughness. Vehicles had an impact on the whole dynamic response of suspension bridge. The response of girders decreased with growth of deck roughness and increased with the growth vehicle spacing. Basing on the measured wind environment at the bridge site, the safe driving rules under different weather conditions were given.