Why do people panic when they see the bridge shaking?
First, although the shaking of the bridge is not the first time, the extent of the shaking directly determines everyone's attention. We can see directly from the video that the abnormal shaking of Humen Bridge is much stronger than that of Yingwuzhou Yangtze River Bridge, which will inevitably cause many people to worry about whether the bridge can still operate safely.
Second, as far as the current urban construction is concerned, bridges are ubiquitous traffic lines. Almost every day, we will shuttle through various bridge structures, large and small. Undoubtedly, everyone can't help but care about their own life safety.
Yingwuzhou Yangtze River Bridge: This bridge has been in normal traffic at present, and professionals have also explained that the shaking amplitude of the bridge deck is indeed within the allowable design range. The reason why the bridge deck swayed like waves was mainly caused by the specific wind conditions at that time.
Third, for ordinary people, we don't know why the bridge vibrates. After all, few people know this in daily life. However, when abnormal vibration occurs on the bridge deck, most people's first reaction will not be to care about whether there are special wind conditions that cause so-called vortex vibration at that time, and they know nothing about the safe range of bridge amplitude, so they will worry about whether the bridge can pass safely under the current situation.
What is the situation of the bridge with abnormal jitter recently?
yingwuzhou yangtze river bridge
First of all, talk about the Yingwuzhou Yangtze River Bridge connecting Fuxing Road in Wuchang District and Maying Road in Hanyang District. This main bridge is 2. 1 km long, and now the construction time is very close. Construction started in August of 20 10, and was officially opened to traffic in February of 20 14. It will only run for more than five years in 2020.
In terms of structural composition, Yingwuzhou Yangtze River Bridge has three pylons to ensure the stability of the bridge body, which not only does not block the urban landscape visually, but also enhances the safety through the selection of materials for each pylon. For example, the herringbone upper tower is made of steel tower.
As far as we know, the Nautilus Island Yangtze River Bridge did have abnormal vibration on April 26th. Some netizens who just passed by the bridge described the vibration characteristics of the bridge as a bit like wave shaking. Soon, professionals announced the cause of the bridge's jitter that day.
It turned out that the special wind condition that fell that day caused the bridge structure to swing, but the amplitude of this vibration was still within the allowable range of design. In a word, there is no safety problem in the structure of this bridge, and it has resumed normal traffic.
humen bridge
Humen Bridge is located in Guangdong Province, with a total length of 15.76 km. It was completed and opened to traffic as early as1June 1997, in which the length of the approach bridge reaches 1 16 km, and the length of the main bridge is about 4.6 km. The main bridge of Humen Bridge spans the waters of Lion Ocean in the Pearl River. There are 23 bridges of different sizes, two large overpass bridges, three tunnels and a large toll station.
On the afternoon of May 5, the video of abnormal jitter with Humen Bridge was madly transmitted. Different from the shaking degree of Yingwuzhou Yangtze River Bridge, it can be directly seen from the video that the shaking of Humen Bridge is very obvious. Although professionals have announced the cause of abnormal vibration (vortex vibration phenomenon), the structure of suspension bridge is safe.
Of course, because the abnormal vibration amplitude of Humen Bridge is really large, and occasionally there will be slight vibration with smaller amplitude, Humen Bridge has not been reopened to traffic for safety reasons, and two-way closure measures have been implemented.
Why do good bridges have vortex-induced vibration?
The expert group has given a preliminary answer to the reason why the vibration amplitude of Humen Bridge is more obvious than that of Yingwuzhou Yangtze River Bridge. We can see that water horses are constantly installed on the Humen Bridge. Because of the specific wind conditions and these water horses changing the aerodynamic shape of the steel box girder, the phenomenon of violent shaking of the bridge deck in the video, the so-called bridge vortex vibration, appears.
Moreover, the expert group also said that in fact, when the wind is small, this large bridge also has vortex vibration, but it is generally difficult to detect because of the small swing amplitude.
In fact, for all non-streamlined objects, as long as they reach a certain constant speed, they can cause eddies separated from the structure code on both sides of the object, and the essential reasons for the abnormal jitter of Yingwuzhou Yangtze River Bridge and Humen Bridge are related to this. Therefore, when we understand the real reasons behind these phenomena, we will not bring unnecessary panic to ourselves until professionals say that the bridge vortex vibration phenomenon will not affect the durability and structural safety of the bridge in the future.