Looking at 2022, two tragedies occurred one after another, one north and one south.
To the north is the stampede in Itaewon, South Korea. On the evening of the 29th local time, 100,000 people squeezed into an alley in Itaewon, , and a serious stampede occurred. More than 100 people have been killed in ;
To the south is the century-old suspension bridge in Gujarat, India collapsed on the 20th, and more than 300 tourists fell into the river, which also caused more than 100 people to die in .
At first glance, the stampede in South Korea is a "man-made disaster" caused by crowds, while India is an "accident" with bridge quality problems. However, after tracing back, there are still many suspicious points pointing to India's management system itself.
Question 1: Hundreds of people are on the bridge at the same time, and the management department does nothing?
It is reported that this suspension bridge has a history of hundreds of years and was once an old wooden suspension bridge. After seven months of luxurious repairs of up to 20 million rupees (about 1.76 million yuan), it reopened on October 26 local time. As a result, something happened on the 29th.
As soon as the incident happened, someone said first: It must be a tofu project! Indian contractors took the kickback!
There is indeed news that the company responsible for repairing suspension bridge is mainly engaged in clocks and home appliances. It has nothing to do with roads and bridges except commuting to and from get off work. Indian police also arrested several relevant personnel as a result.
But in fact, after analyzing the entire pile incident, this company is really a bit "unfair", because even if the corruption is cracked down on, the bridge will still collapse after exceeding the carrying capacity. This thing is actually not as solid as we imagined.
First of all, under each bridge, it is almost empty. Needless to say, suspension bridge , but even a bridge with a pier is one pier each, and the bridge can pass freely. It is impossible for any bridge to block the entire under the bridge like the Great Wall. This kind of bridge is indeed as strong as the Great Wall, but when the morning and evening rush hour, the workers who were blocked by it would probably cry to Meng Jiangnu .
The reason why most bridges are "sturdy" is that when engineers design bridges, they will share the weight of the bridge itself with the weight of vehicles and people on the bridge by the load-bearing structure. The so-called load-bearing structure can be understood as various triangles, cones and arches that make up the bridge.
These geometry can increase the moment of inertia of the bridge. In layman's terms, it means that increases the ability of bridge board to resist deformation . Not to mention steel and cement, even if a piece of printing paper is folded, it can withstand a considerable weight and can even be used as furniture.
For example, if you step on a piece of paper at home, you will step on it. But if you step on the origami homework like the picture thrown by the naughty child, it will probably be "bloody flows into a river".
In addition, if an extremely heavy thing is pressed on the bridge, the pressure it brings to the bridge deck is first manifested as a pulling force, which puts the bridge repair material to the test. These tension forces are transmitted by triangular sides, arched arcs and other structures, and fall onto the piers and become the pressure of the piers. The bridge piers are deeply penetrated into the earth, so there is no need to worry about being unable to bear it.
However, the load-bearing capacity of a bridge is limited and is limited by materials and structure. If the things on the bridge are too heavy, the piers will have to stop in advance.
According to local Indian media reports, there were at least 300-400 people on the bridge when the accident occurred, and some parties even claimed that there were 500 people. Moreover, the suspension bridge management did not take any measures to limit the flow of people , and only knew how to buy tickets. Witnesses at the scene also said that the cause of the accident was that the bridge deck suddenly broke, and people on the bridge fell into the water. From this point of view, is overweight, which is the main reason for the accident. has not run away.
Not only in India, but also in the world, bridge accidents caused by overweight have occurred.
The reason is very simple: there must be a fixed load-bearing limit when designing a bridge, which is also the red line of the bridge. However, for safety, it is impossible to step on this red line to test, so local road traffic management departments will set up a stricter weight limit.It slightly exceeded the weight limit but did not reach the true red line of the bridge, so it can actually pass safely.
Because of this principle, it is easy to think of, so everyone is exploring it on the verge of danger. After all, the cost of taking a bus is fixed, and installing more on the bus will make more money.
The most serious consequence of passenger vehicles is that the vehicle is too heavy and it is difficult to stop when driving. This may seriously endanger the safety of passengers' lives and other vehicles' driving safety, but it is just a drizzle for the bridge.
The real threat is overloading trucks. Some drivers will inevitably cause serious overload of trucks in order to speed up the construction period and save costs. This truck is respected by other drivers as a "land cruiser" and cannot be avoided. There are many thrilling accidents caused by these overload trucks.
India's suspension bridge accident must have been caused by the management department. No matter how much I want to buy tickets, hundreds of people should not be squeezed into a scenic spot suspension bridge at once. The force exceeds the red line of the bridge, and of course there will be an accident.
Question 2: Who is "shaking" the suspension bridge, making it the last straw that overwhelms the bridge?
However, in addition to its size, the force also has direction. When designing a bridge, the first thing you consider is how to withstand the pressure on the bridge deck, and the pressure is straight up and down. The structure mentioned before is mainly to cope with this pressure. In addition, the bridge will also consider the force brought by the wind to impact the bridge from the side, which is called the wind load of the bridge. In short, the wind load allows the bridge to withstand a certain degree of shaking.
The area where the Hong Kong-Zhuhai-Macao Bridge is located often faces typhoon directly. After the bridge was repaired, the front face was 17-level Typhoon Mangosteen without any damage, relying on strong wind load.
However, not every bridge is designed according to the standards of the Hong Kong-Zhuhai-Macao Bridge. The bridge in India where the accident occurred this time is just a scenic spot suspension bridge for viewing and its carrying capacity is worrying.
Moreover, according to some witnesses, when the bridge was already crowded with tourists, several men in their twenties actually deliberately shook the bridge. The surveillance video on the bridge also records this scene: a man in a white shirt holds the protective nets on both sides, shaking in vain, and the suspension bridge breaks the next second.
Someone has noticed that the man in the video did not seem to shake the suspension bridge hard, but why did such a serious accident cause? The overweight and weak bridge load mentioned before may lead to this consequence. However, there is another reason, which is that resonance .
Each object has a physical property called natural frequency. In short, if anything - including the human body - is placed there without shock, and a shock is a fixed frequency. You hang it up and knock it like a bell. No matter how much effort you use, after knocking it, the frequency of the object's vibration will immediately stabilize.
This frequency is only affected by the nature of the object itself, as well as the ropes and frames you use to lift it. This is the natural frequency of the object. When the vibration applied by the outside world matches the natural frequency of the object, the amplitude of the vibration of the object will increase.
Sometimes, when we are in a noisy environment, we will feel our heartbeat faster and feel nauseous. This is because the vibration frequency of the sound happens to meet the natural frequency of our internal organs, causing the internal organs to start vibrating and trembling, and in severe cases, it can even cause death. When the missile attacked some areas, some people did not suffer direct attacks, but suffered "internal injuries" such as internal bleeding. This is the damage caused by resonance.
Each bridge naturally has its own natural frequency. When this artificial shaking accidentally coincides with the natural frequency of the bridge, it will cause the effect of "complementary and twice the result with half the effort" . In other words, those who shake the bridge will suddenly find that the bridge is like it is alive and begin to sway wildly. At this time, it will be difficult to regret it again.
Accident similar to "shake, shake the grandmother's bridge" has actually happened in our country.Fortunately, the bridge where the accident occurred was a suspension bridge in the water park. The purpose of the design was to make tourists shake, and it was very close to the water surface, so there were no casualties.
Water Park suspension bridge broke, which seemed to be just a false alarm. Anyway, the people on the bridge are also trying to shake each other into the water. The quality of the bridges of my infrastructure maniac is definitely nothing to say. However, this does not mean that the tragedy that happened in India will not happen elsewhere .
There is no easy word for adults. When you go out to travel, you are also to release the pressure and enjoy life. However, 's own happiness must not be based on threatening the safety of others.
Many scenic spots have the so-called "Internet celebrity sling bridge", and there are often reports that tourists with worry-properties are shaking the suspension bridge and are criticized by others. There was no serious accident, it can only be said that the tourists are lucky and lucky. In the future, when you walk on the suspension bridge again, you should challenge your self-control and don’t shake the bridge body at will, and challenge the bearing capacity of the bridge.
