What are the measures and means for bridges to resist earthquakes and winds?

Only half of the landlord's questions can be answered.

The wind-induced vibration of the bridge structure is divided into many types, such as the main girder (steel box girder) and the cable towervortex excitation vibrationIn addition, there are also different forms (or coupling) of wind-induced vibration such as cable-stayed cables and booms, such as vortex vibration, wind and rain excitation, wake vibration, etc.

A common control method, for wind-induced vibration of steel box girders, can be reduced by selecting a "good" aerodynamic shape. For example, the steel box girder section of the Xiyanmen Bridge was determined after wind tunnel test & CFD numerical simulation of different shapes and box-spaces. Of course, you can also use a damper to increase the structural systemdampingto reduce the wind-induced dynamic response.

For cable-stayed cables, booms and other components, because of their high flexibility, they are very sensitive to wind-induced vibrations. The usual control method is to use a damper, and some bridges use auxiliary cables to reduce the effective length of the cable, thereby improving the dynamic characteristics. However, there is a problem with this method, that is, it destroys the beauty of the cable load-bearing system bridge, so people have proposed other methods.

For example, adding some bulges or spirals to the surface of the cable can effectively inhibit the vortex of the cylinder from falling off and inhibit the formation of karman vortexesDrag coefficientand lift pulsation will be significantly reduced to achieve controlAmplitudeThe purpose of. These methods have been successfully applied in actual bridge structures.

In addition, there are still in theTheoretical explorationSeveral active control methods in the stage, such as blowing, suction control, traveling wave wall control, etc., these flow control methods born in the fields of aviation and bionics are currently hot and cutting-edge topics in wind-induced vibration control. The common idea of these methods is to change the solid wallBoundary conditionsto reduce the resistance of the blunt body in the flow field and achieve the purpose of controlling vibration. For example, dolphins will follow when swimming at high speedflow fieldto change the skin folds on its surface, and achieve the effect of drag reduction with "flexible boundaries".

Of course, the flow control method is used in bridge structures, and it also depends on intelligent materials and structuresMonitoring technologydevelopment.

Above, throw bricks to attract jade.