World Trade Center

Like most other people in the world, forgetting the dreadful scene of the two burning towers in the York city, seems rather impossible. The entire world shuddered from what it was then and what it is today. Every time people visited the city, a huge crowd would gather around the Twin Towers, the World Trade Centers, to see its immense height and powerful engineering. But things changed forever for the new city on the September 11th, 2001. With initial news of two planes crashing into the towers, the world trade center video soon flashed up across all news channels. Ever since then, people visit the city to stand and mourn around ground zero, the very place where the twin towers stood superior to the other skyscrapers. But the question still remains on how the two strong buildings fell down like a stack of cards. Here is a short brief about the investigation performed by experts and engineers that followed after the attack.

The fall

1. Impact of the terrorist planes

Hijacked by the terrorists, when the two huge Boeing planes struck the huge towers, nearly about 10,000 gallons viz. about 38 kilolitres of jet fuel from the planes dripped over from the planes onto the towers, causing an gargantuan fire. However, the impact of the planes and the sudden burst of flames did not cause the world trade center collapse. The reason for the fall was its redundant design and structure.

The world trade center towers had about 244 columns surrounding a single central core. This further housed the stairwells, elevators, utilities and other mechanical systems. Hence, when a few of these columns were destroyed in the clash, the others still stood by supporting the building.

2. Heat of the fire

With the impact from the planes, sprinkler system stopped functioning and hence the fire became intense. The jet fuels burn at a high temperature of 800° – 1500°F but it is still not hot enough to melt steel which was used for the construction of the huge towers. However, the steel structures used in the construction lose their strength due to the heat.

3. Collapsing floors

The fire that began from the planes, spread through the entire floor thus bringing down the weakened floors. The crashing down of these floors with high momentum and weight crushed the successive floors below them.

Why the towers looked flat after the fall?

Lightweight steel was used in the making of the towers around the central core and the towers had 95% air which thus caused the huge fall killing hundreds of world trade center people.