Analysis Theory And Field Measurement Of Wind-induced Response Of Long-span Truss Girder Suspension Bridges In Mountainous Canyon

The paper first briefly introduced the wind resistance development process and research status of large-span truss girder in mountainous areas.According to the field measurement of the wind field and the wind-induced response of the Sunxi River Bridge,the distribution of the wind field characteristics of the mountain canyon along the bridge span was obtained.The internal relationship between the wind field in the mountain canyon and the windinduced response characteristics of the large-span bridge in the mountain canyon was established.At the same time,the buffeting force characteristics and self-excited force of truss girder are deeply studied by using high-frequency dynamic balance force measurement test and self-excited force forced vibration test.The calculation and analysis method of the buffeting response of the long-span bridge in the mountain canyon was verified by the measured results and the wind tunnel test results.And by adjusting the wind field characteristic parameters and the aerodynamic characteristic parameters of the truss girder,the influencing factors of the buffeting response of the large-span truss girder bridge in the mountainous area were studied.The main research contents of this paper are:1.In this paper,by arranging 9 propeller anemometers and 5 ultrasonic anemometers along the bridge span on a large-span truss girder bridge in a mountain canyon,the wind field distribution along the bridge span has been studied for a long time(one year).The measured results of the mean wind field characteristics(wind speed,wind direction,wind angle of attack)and turbulent wind field characteristics(turbulence intensity,turbulence integral scale,fluctuating wind power spectrum)of the wind field at the bridge location in the mountain canyon were statistically analyzed.The differences between the characteristics of the wind field in the typical period and the statistical average value of the whole year were shown,the uneven distribution of the wind field in the mountain canyon along the bridge span was analyzed statistically,and the statistical mathematical model of some wind field parameters was given.2.Based on the GNSS monitoring system,four monitoring points were arranged along the span direction of the long-span truss bridge in the mountainous area to monitor the windinduced response of the bridge for a long time(one year).Combined with the measured results of the wind field,the relationship between the wind field parameters(wind speed,wind angle of attack,wind deflection angle,turbulence degree)and the statistical characteristics of the wind-induced response of the large-span truss girder.Combined with the characteristics of the wind field during typical strong wind periods,the buffeting response of the long-span truss girder bridge in the mountain canyon during the corresponding typical period was obtained,which provides a reference for the theoretical calculation of buffeting.3.Four kinds of turbulent wind fields close to the wind field of mountain canyons were simulated in the wind tunnel by using grids(with different ventilation rates)and spires,and the variation rules of turbulence characteristics(turbulence degree,turbulence integral scale,and pulsating wind power spectrum)were analyzed.Using the active control grid independently developed by the team,a gust field(two-dimensional fully correlated simple harmonic wind field)was established in the wind tunnel,and its two-dimensional characteristics were tested.The establishment of various types of wind fields provides a guarantee for the subsequent wind tunnel test research on factors affecting the wind-induced response of truss girder.4.Based on the various turbulent wind fields simulated in the wind tunnel,the correlation between the aerodynamic admittance function and the aerodynamic force of the truss girder was studied in detail by combining the wind tunnel test and calculation analysis method.Using the concept of equivalent section of truss girder,the identification method of aerodynamic admittance of truss girder was obtained.According to the wind tunnel test results,the empirical formula of two-dimensional and one wavenumber aerodynamic admittance of truss girder and the empirical formula of span-direction coherence of truss girder were obtained.The influence of turbulent flow characteristics on the buffeting force characteristics was summarized.It provides basic data for the buffeting response calculation of long-span truss girder bridges in mountain canyons.5.By identifying the two-dimensional aerodynamic admittance of the truss girder in the gust wind field(two-dimensional fully correlated simple harmonic wind field),the calculation method of directly identifying the aerodynamic admittance of the truss girder in the three-dimensional turbulent wind field was verified.Based on the forced vibration test,the flutter derivatives of large-span truss beams in mountain canyons were identified in the simulated different turbulent wind fields,and the influence of wind field characteristics on the flutter derivatives was obtained.It provides a reference for studying the variation law of the buffeting response of long-span truss girder bridges in mountain canyons under different wind field parameters and buffeting force characteristics.6.Finally,based on the SRSS method,combined with the field measured wind characteristics,the buffeting force characteristics and flutter derivatives obtained from the wind tunnel test,the buffeting response of the long-span truss girder bridge in the mountain canyon was calculated,and the calculation method was verified by the measured response results of the typical period.The influence of wind field characteristics and truss girder buffeting force characteristics on the buffeting response of long-span truss girder bridges was calculated by changing parameters.