Study On Correlation Of Buffeting Force And Identification Of Aerodynamic Admittance Function Of Bridge Section Under Pulsating Airflow

With the rapid development of bridge construction technology in China,the record of long-span bridges is constantly refreshed,and the bridges become more flexible.The analysis of buffeting of long-span bridges has become an important factor in the wind-resistant design of bridges.The aerodynamic admittance function and the cross-vibration force Correlation is a control parameter for the accuracy of buffeting response analysis.Due to the complexity of the aerodynamic admittance function and the limitations of experimental technical conditions,the existing aerodynamic admittance identification methods and recognition results have the disadvantages of large dispersion and low repeatability,which has become a wind-resistant design for long-span bridges in China.Based on the pulsating wind field formed by the along-wind and vertical-wind active turbulence generater,this paper adopts the segmental model forced vibration test,the full bridge aeroelastic model test and the Ansys transient analysis numerical calculation and other research methods to study the aerodynamics admittance function,the spatial distribution characteristics of the buffeting force and the buffeting response characteristics of the rectangular section.The main contents and results of the research are as follows.(1)By studying the characteristics of the pulsating flow field formed by the along-wind and vertical-wind active turbulence generater,the flow field has a good harmonicity,uniformity and single cycle repeatability.A single frequency quasi-sinusoidal pulsating wind field and a multi-harmonic combined pulsating wind field can be formed in the wind tunnel and created favorable conditions for the experiment.(2)Based on the formed pulsating wind field,under single frequency quasi-sinusoidal pulsating wind field,six aerodynamic admittance function amplitude of thin plate section and rectangular section are identified with three differe nt aerodynamic admittance identification methods by the forced vibration segment model stiffness test.The influence of different wind field types and wind field parameters on the aerodynamic admittance function is compared,and compared with the Sears theoretical function.It is found that for the rectangular section,the identification of the resistance aerodynamic admittance in the along-wind pulsating flow field is better than other buffeting force component.In the vertical-wind pulsating flow field,the aerodynamic admittance amplitude of the lift and lift moment is more accurate,and the wind angle of attack,the pulsating wind frequency and the average wind speed of the incoming flow have a significant influence on the aerodynamic admittance amplitude.(3)Based on the along-wind pulsating flow field,the aerodynamic admittance function between the different pulsating wind harmonic components and the corresponding buffeting force is identified.By comparing the first-order correspondingly identified aerodynamic admittance amplitude and the second-order corresponding aerodynamic admittance amplitude The aerodynamic admittance amplitude curve proves the nonlinear of the buffeting force.(4)By studying the correlation of the rectangular section segment model and the aeroelastic model’s buffeting force,analyzing the different parameters’ on the the correlation,and the negative correlation are obtained between the correlation of the buffeting force and the pulsating wind frequency,space.Combining the Matlab elliptic filter,the buffeting force and self-exciting force are successfully separated.It is concluded that the self-exciting force can improve the cross-correlation of the buffeting force.By the parameter fitting of the buffeting resistance correlation,the fitting effect proves to be better with coherent function model to the buffeting force.(5)By the full-bridge rigid model test,the aeroelastic model test combined with the Ansys transient analysis numerical calculation,the buffeting response characteristics are studied.It is found that the wind speed,the pulsating wind frequency and the wind angle of attack have a significant influence on the buffeting response.With the wind speed increases,the buffeting response increases gradually.In a certain frequency range,the buffeting response increases with the increase of the pulsating wind frequency.If exceeds the range,there is a decreases trend,and the influence of wind angle of attack on the buffeting response in high frequency part is more significant than the lower.