On the afternoon of May 5, 2020, the Humen Bridge shook abnormally, and the whole bridge section was completely closed in both directions, and no traffic was allowed. On May 6th, Guangdong Communications Group reported that the vibration system of Humen Bridge was vortex vibration and the suspension bridge was structurally safe.
Anyone who has studied physics knows that bridges will vibrate at a certain frequency. On May 5th, the deck undulation was said to be caused by the guardrail retaining wall (water horse) on both sides of Humen Bridge, which was subsequently removed, but the deck still shook that night. On the morning of the 6th, the staff of Guangdong Humen Bridge Company said that under normal circumstances, such jitter has no effect on the bridge deck structure, and further analysis and research by experts are needed.
The vibration of Humen Bridge is called vortex vibration. The occurrence of vortex vibration does not necessarily require particularly strong wind, and low-speed wind is also possible, mainly because the wind speed coincides with the natural vibration frequency of the bridge structure. That's what we call * * * vibration in physics.
Zhang Xinmin, deputy chief engineer of Humen Bridge Overhaul Office, said in an interview with CCTV news on the evening of 5th that flutter and vortex vibration will occur in long-span suspension bridges under the action of wind. Simply put, flutter may cause torsion and damage the bridge structure, while vortex vibration will not affect the bridge structure, but will only affect the driving comfort. Humen Bridge is a long-span suspension bridge with flexible structure. After the vibration occurred, the water horse on the bridge deck was removed, the wind speed decreased, and the vortex vibration was much smaller. The reason why there is still vibration may be because of inertia, and the vortex vibration will be automatically eliminated.
Humen Bridge, as a suspension bridge structure, is called suspension bridge. Many suspenders are suspended from cables to hang the deck. Stiffening beams are usually arranged between the bridge deck and the suspenders to form a combined system with cables to reduce deflection and deformation caused by loads.
Suspension bridges are more flexible and suitable for windy and earthquake areas, and relatively stable bridges must be stronger and heavier in these areas. The suspension bridge is not firm, so traffic must be temporarily suspended in case of strong wind. Suspension bridges should not be used as heavy railway bridges.