The US World Trade Center collapsed. Was it the plane crashing and burning, or was it demolished by controlled blasting?

9·11 incident It has been 20 years ago, but the discussion about that terrorist attack is still attracting attention. As the largest terrorist attack on the United States since the beginning of the new century, this incident did cause many casualties.

Why did the twin towers collapse in the September 11 incident?

The original two 110-story World Trade Towers were landmark buildings in Manhattan, New York. After two passenger plane collisions, the two buildings collapsed. People have different opinions on the reasons for the collapse of the two buildings, because the impact of the passenger plane only caused a part of the upper part of the building to break, and did not cause an impact on the overall structure of the building.

So the collapse of the building was not mainly caused by the impact of the passenger plane. Other claims include the high temperature melting of the steel, and some people claim that the incident was caused by directional blasting. Because the building collapsed and raised a lot of dust, the scene was very similar to directional blasting. If you want to know why the building really collapsed, you have to start with the structure of the building.

In 1961, the Port Authority of New York and New Jersey decided to build the World Trade Center. It was Yamazaki Miro and Ross and his sons who were responsible for the construction of the building. Out of consideration of construction cost, Yamazaki gave a set of design plans. The interior of the building is a huge elevator inner tube built with steel columns and reinforced concrete. Externally, 236 steel columns are used to make the frame of the external wall, and a lightweight steel truss is used as a fixed part between the two. The floor is laid with a 10 cm thick cement board.

The design of the twin tower is the main reason for the collapse of the building.

is not only faster to build, but it is also light enough to ensure the basic strength of the building, and it will not shake under strong wind conditions.

However, the twin towers did not consider the event of an aircraft collision before the design, so as to ensure the basic strength of the design,Instead, the building collapsed. The passenger plane of the September 11 incident hit the Twin Towers, only to break a few steel columns on the outer wall after the impact. As there were other steel pillars, the building did not collapse immediately after the impact.

Both passenger planes carried 90,000 liters of fuel, which burned violently in the building after the impact. Some people have speculated that the collapse of the Twin Towers was due to the high temperature generated by the burning of the fuel oil, which caused the steel to be roasted. In fact, the strength of steel in a high temperature environment is indeed greatly affected, but the baking is not enough. The fuel burns at a high temperature, but it has not yet melted steel. After the impact, thick smoke billowed at the impact site, showing that the fuel was not fully burned.

The most likely cause of the collapse of the twin towers may be the floor design with limited load-bearing capacity. The steel slab truss connecting the floor slabs is no longer strong in the high temperature environment, and the expansion degree of the outer wall steel column is different from that of the steel slab truss, resulting in the truss falling off. It hits the floor of the next floor, and the floor where it hits has this problem.

These slabs fell on the first floor after falling. At the time of design, a floor slab carried a maximum of 1,300 tons, so the floor slab kept falling because it could not bear such a heavy weight. There was no fire-fighting facility for fire in the whole building, and the steel columns on the outer wall could not support the collapsed building, so the whole building collapsed quickly in a short period of time.

The collapse of the twin towers during the 9·11 incident gave designers more inspiration

The collapse of the World Trade Center also gave some inspiration to the construction of other skyscrapers later. Before designing such a tall building, designers will have more Consider the scene after the building was attacked by the air. By adjusting the steel structure of the building, the building is made stronger, so that it will not be subjected to a collision, which will cause the entire building to collapse completely.

If the World Trade Center does not completely collapse, it will not cause so many casualties. This case looks like an ordinary terrorist attack, but in fact it may have been precisely planned by terrorists. If they don’t understand the structure of the building,It may not hit the upper level of the building, but the lower level of the building.

After that, the United States launched a strike against al-Qaeda. After the elimination of al-Qaeda, the possibility of such a terrorist attack again is very small. The 9/11 incident has also become a disaster that Americans cannot bear to look back on.

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