Non-stationary Buffeting Displacement Response Analysis In Time-domain Of Long-span Suspension Bridge

With the gradually increasing of bridge span in recent decades, the stiffness ofbridges is become smaller and smaller. Wind-induced vibration is highlighted daysand days, the wind resistance design of bridge has become the essential part of thedesign of bridges. The calculation and analysis of bridge buffeting response has beenmature after many years of development, however, it's indicated that the fluctuatingwind speed has the characteristics of non-sationary in complex terrain of mountainand wind environment by the observation and measured wind speed datas. That is tosay, it cannot be regarded as a stationary random process to calculate the buffetingresponse. The traditional stationary buffeting response analysis cannot meets thebridge response analysis in such wind environment. In this paper, the non-stationarybuffeting response in complex wind environment is researched, the wind is regardedas a non-stationary random process, and the buffeting response of large spansuspension bridge is obtained, which has a great significance to the bridge design andsafety assessment in complex terrain such as mountain.In this research, the method of harmonic synthesis is used to produce stationaryfluctuating wind of multiple points with three-dimensional space. Based on thetheory of evolution of spectrum, the modulation function is chosed to change thefluctuating wind form stationary to non-stationary wind speed, and then the timehistory of wind load is obtained; ANSYS finite element model is established, basedon the APDL language, non-stationary buffeting response analysis program isprogramed. Wind load are added to the main girder and cable, bridge tower andbridge pier to analyse the bridge buffeting response in time domain. Finally?parametric analysis is done to researceh the influence of wind angle of deck andaerodynamic admittance, self-excited force on non-stationary buffeting response.Researches show that: there is a big difference between Non-stationary windturbulence intensity values and stationary values, which has a close realation to thechosing of modulation function. The non-stationary buffeting response of the deck ofbridge is stronger than the bridge tower, the maximum appears in the transversebridge direction nearby the cross location. The wind attack angle has a big influnenceon the main girder buffeting response in the vertical diraction, and no influence orlittle influence on the response in the cross direction and the direction of angle oftwist. Bridge tower is almost not affected by wind attack angle, while the buffetingresponse of bridge is effected significantly by the aerodynamic admittance. Afterconsidering the aerodynamic admittance, buffeting response is decreased obviously, so, it will be safe when the aerodynamic admittance is not considered in practicalengineering. Self-excited force have divergent effect, the bridge buffeting responseincreases several times after considering self-excited force, especially for girdervertical response, even play a leading role. The vertical non-stationary buffetingresponse of girder is far greater than that without considering self-excited force.Engineers should gave enough attention in practical engineering, stiffness of themainspan shoulded be improved, as far as possible, to avoid the the couplingvibration effect of wind and structure.