Wind-induced Vibration Response Of Flexible Aerodynamic Measures And Its Application

Large span bridge structures are prone to wind induced vibration under wind loads due to their low frequency.In order to improve the wind resistance stability of large span bridges,aerodynamic measures such as stabilizing plates,flow suppression plates,partitions,skirts,deflectors,and flow barriers are commonly used.These aerodynamic measures are generally made of steel plates and other materials,and can be considered rigid aerodynamic measures.Inspired by the flow control of elastic structures in nature,this paper attempts to introduce flexible and elastic structures as aerodynamic measures to improve the wind stability performance of long span bridges.Select typical bluff body sections and Π beam section as the research object,combined with numerical simulation and wind tunnel tests,the effects of flexible aerodynamic measures on suppressing wind induced vibration of bridges are studied,the working mechanism of flexible aerodynamic measures is explored,and the methods for suppressing wind induced vibration of large span bridges are enriched and improved.The main research contents include:(1)Taking a typical bluff body section when Reynolds number is 200 as the research object,rigid splitter plates with different sizes(L/D=1-4)and flexible splitter plates with different parameters(L/D=3)are arranged at the tail of the bluff body along the central axis,and their effects on the drag coefficient,lift coefficient,Strouhal number,and flow field distribution are analyzed.Compared to rigid splitter plates,the advantage of flexible plates is that their active flapping deformation further reduces the resistance coefficient.The flapping frequency of flexible splitter plates is consistent with the section vortex shedding frequency,and the Strouhal number can be further reduced by changing the flapping frequency of flexible splitter plates.(2)Based on the actual project,The vortex-induced vibration response of the original section of the Π-shaped main beam was analyzed when the width to height ratio was 8.35,and the results showed that the main beam had very obvious vortex-induced vibration phenomena at 0 °,+3 °,and-3 ° attack angles.The vertical bending vortex-induced vibration response was in an obvious double locking region,while the torsional vortex-induced vibration only existed in a single vortex-induced vibration region.(3)Replacing the common rigid aerodynamic measures with flexible materials,the wind tunnel test of a segmental model was conducted to record the vortex-induced vibration response curves of the model under various operating conditions,such as the flexible inverted L-plate,the flexible lower central stabilizer plate,and the flexible lower side stabilizer plate.Compared with the original section data,it is found that the installation of flexible inverted L-plates has a certain inhibitory effect on both vertical and torsional vortexes of the main beam,and the inhibitory effect on torsional vortexes is more prominent,especially under D2-2 working conditions;The flapping changes of the flexible lower central stabilizing plate and the flexible lower stabilizing plate do not significantly interfere with the vortex structure of the flow field near the main beam,and do not absolutely suppress the vortex vibration of the main beam.(4)The flow field of the original section of the main beam was analyzed through numerical simulation,and the flapping deformation of the flexible inverted L-plate under D2-2 working condition was simulated using the fluid-solid coupling method.The flow field results showed that the vibration suppression effect of this working condition on the main beam mainly had three points: the diversion effect of the flexible inverted L-plate at the leading edge weakened the separation degree of the upper and lower surfaces of the section,and the periodic pressure difference on the section was reduced;The vortex structure generated by the flapping of the flexible inverted L-plate at the trailing edge has a certain interference effect on the nearby flow field;The vortex shedding direction at the tail of the main beam under the macro flow field is changed.