Study On Wind-induced Vibration Characteristics Of H-shaped Suspender With Small Aspect Ratio Considering Incoming Flow Characteristics

In recent years,the pace of construction of long-span bridges in my country has been accelerating.H-shaped suspender are widely used in long-span arch bridges or steel truss bridges due to their strong bending resistance and convenient manufacturing and construction.However,the H-shaped suspender is light in weight,soft in structure,small in damping ratio,and its blunt aerodynamic shape will cause significant flow separation.It is easy to be affected by the natural wind of the wind direction angle in the range of 0°～360°,and it is very prone to wind-induced vibration phenomena such as vortex-induced vibration(VIV),galloping and flutter.This paper conducts the following research on the H-shaped suspender with small aspect ratio(B/D=1.9):(1)Based on the test results of the H-shaped section model,it is found that the structural damping ratio and structural mass have a significant impact on the wind-induced vibration characteristics of the H-shaped suspender model: increasing the structural damping ratio or structural mass can effectively suppress the occurrence of VIV under the wind attack angle of0° and the increase of the damping ratio makes the onset wind speed of the torsional flutter at the 40° wind attack angle further lag behind.The difference is that the torsional soft flutter at the 30° wind attack angle can be effectively suppressed by properly reducing the structural mass.At the same time,it is found that At the same time,it is found that the incoming turbulence with different turbulence intensity and different turbulence integration scale has a certain inhibitory effect on the eddy vibration under the wind attack angle of 0°,and the influence degree of the turbulent flow intensity is stronger than that of the turbulence integration scale.(2)According to the test results of the H-shaped section aeroelastic model,it is found that increasing structural damping ratio or setting a turbulent wind field can effectively suppress galloping at 0° windage angle and torsional soft flutter at 30° windage angle,Increase the flutter critical wind speed of the H-shaped suspender.Conducted 20 groups of wind vibration tests with different web and flange opening ratios,and found that the opening ratio of the flange was8.1% or 16.2%,and the opening ratio of the web was 0 or 31.9%,which can be used as an improved H-shaped suspender.The aerodynamic measure scheme for galloping in the crosswind direction;the flange opening ratio of 24.9% can significantly eliminate the flutter instability at a windage angle of 30°,and improve the aerodynamic stability of the H-shaped section aeroelastic model.(3)Using CFD numerical simulation technology,it is verified that the uniformity of the wind field between the airfoil support devices in the new wind tunnel is good,and there is no obvious vortex shedding,and the support is effectively adjusted by adjusting the angle of the support relative to the incoming wind.The boundary layer thickness of the inner wind field is reduced from 20 cm to 6～8cm.In addition,comparing the two-degree-of-freedom coupling device used in the traditional wind tunnel test with the three-degree-of-freedom coupling device in this paper,it is found that different degrees of freedom coupling technologies have obvious effects on vibration phenomena,which are manifested as torsional vortex vibration and torsional flutter respectively.Comparing the vorticity evolution and instantaneous pressure contours of the two three-degree-of-freedom coupling cases with large differences in the strong axis stiffness,it explains the obvious difference in the torsional amplitude at high wind speeds.