Study On Non-Stationary Buffeting Force And Dynamic Response Of Long-Span Suspension Bridges In Mountainous Areas

With the rapid development of society,more and more long-span bridges are built in the deep mountain and canyon areas under complex wind conditions in order to meet the travel needs of more people.But with the increasing span of the bridge,the structure of the bridge becomes lighter with decreased strength,and the bridge structure is more sensitive to the wind.In addition,according to the analysis of the measured data,the wind speed in mountain area is a random and non-stationary process,which has strong non-stationary characteristics.If the traditional stationary wind speed model is still used to analyze the buffeting response of the bridge,a large error will be caused.Therefore,based on the nonstationary wind speed model of large-span bridges in mountainous areas,this paper analyzes the buffeting response of the simulated wind speed timing process,which will be of great significance to the wind resistance design and safety assessment of large-span bridges in mountainous areas.This paper mainly studies the following aspects:(1)Based on the health monitoring system of a suspension bridge in mountainous area,this paper collects the samples of measured wind speed timing process,analyzes its wind characteristics,and constructs a model of non-stationary wind speed in mountainous area.Based on the harmonic synthesis method and evolution spectrum theory,we simulate the non-stationary fluctuating wind process of the bridge,estimate the spectrum of the simulated wind speed,and compare it with the corresponding target spectrum to test its rationality.The results show that the value of non-stationary turbulence intensity is less than that of stationary turbulence intensity.(2)According to the measured wind speed data collected by the anemometer sensor of a suspension bridge and the db10 wavelet in the toolbox,this paper extracts the measured time-varying average wind speed,and analyzes the time-varying characteristics of the wind speed.It compares the fluctuating power spectrum of the measured downwind and vertical fluctuating wind speed samples with the standard power spectrum,and verifies the rationality of using the non-stationary wind speed model in the mountain area.(3)According to the simulation of non-stationary time dependent average wind speed time history of fluctuating wind speed and extraction,the wind load in time domain,based on APDL language will get wind load is loaded into the finite element model of buffeting response analysis,comparative analysis is mainly focused on the stable under the action of pulsating wind and non-stationary pulsating wind response results,discussed the different wavelet function is adopted to time-varying average wind trend term extraction,whether considering the aerodynamic admittance,the wind attack Angle change on non-stationary buffeting response.The results show that the non-stationary chattering response of the bridge is greater than that of the stationary chattering response,and the maximum value appears in the mid-span of the main beam,which indicates that the wind speed model in the complex wind field such as mountain area is reasonable to represent the superposition of time-varying mean wind speed and non-stationary pulsating wind speed.Db10 wavelet function is better than other wavelet functions to extract the trend term of time-varying average wind speed.If the influence of the aerodynamic admittance function on the chattering response of the bridge is considered,the resulting displacement value will be reduced.On the contrary,if the displacement response value is not considered,the displacement response value will be increased and the wind-resistant design of the bridge will be more safe.With the change of wind attack Angle,the response of non-stationary chattering of the structure also changes,and the torsional displacement increases obviously.Therefore attention should be paid to it in practical engineering and some measures should be taken if necessary.