Mitigation On Wind Loads Of Girders Of Longspan Bridges By Using A Flapping Flow Control

The development of long-span bridges can enhance regional connections and greatly promote local economic and social development.However,as the span increases,the stiffness of the main structure of the bridge decreases,the flexibility increases,the damping decreases,and it is susceptible to wind loads.The bridge has a large wind-induced vibration,and the cross-sea bridge is even more serious.The wind effect of the main beam of the long-span bridge is one of the most prominent dynamic effects at present.The flutter can cause serious damage or even damage to the long-span bridge.Although the vortex-induced vibration will not cause the bridge to break,but the frequency is high,Brings potential structural fatigue damage.Therefore,how to reduce the wind load and reduce the dynamic effect of wind load on the bridge is a hot issue in the study of wind resistance of bridges.In this paper,the following research work is carried out on wind load control of main beam of long-span suspension bridge:In the first step,a rectangular section model and a main beam model based on the Danish Great Belt Bridge are designed respectively.The geometric shape and flap angle of the corresponding flap flow control are designed for the two models.The test platform and design model of the fixed model test stage are built.Wind tunnel pressure test,determine PIV test plan and working conditions.Secondly,the wind tunnel test with the flap plate model is carried out.By changing the front and rear flap angles and their combinations,the wind angle of attack with large wind-induced response of the uncontrolled model is obtained.It is also proved that a reasonable change of the front flap angle in this interval can effectively reduce the potential wind-induced response.Finally,the wind tunnel test of the main girder model with flaps is carried out.A fixed length triangular flap is selected.By changing the front and rear flap angles and their combinations,it is proved that the asymmetric cross section bridge has an asymmetric peak interval.And once again verify that the flap has a good control effect.Further,the front flaps in the upper and lower asymmetric main girder wind load flap control play a major role.