Article Summary 6

Article 6 Summary

There have been many reports for the reason behind the collapse of the World Trade Center.

Some things have proven to be incorrect though, such as the steel softening due to elevated temperatures. It is because of this that the structure of the World Trade Center was analyzed in order to create guidelines for future structures.

Because there is still speculation of whether or not the building were structurally deficient, the authors are trying to figure out what is true about its collapsing.

In the essay they specifically look into the following things;

The airplane impact with damage to the columns.

The resulting fire with loss of steel strength and distortion

The collapse, which generally occurred inward without significant tipping

It was built from 1960-1970. In order to make the building withstand a certain wind load, a “perimeter tube” was installed. It was made to support the weight of the tower, and house elevators, stairwells, and the mechanical risers and utilities.

It was made in an egg crate structure. Because of this it was one the most resilient towers because if a few columns were lost, it would shift itself into adjacent columns and would stay standing.

The buildings had more than 1,000 times the mass of the aircraft and had been designed to resist steady wind loads of 30 times the weight of the aircraft, which made the fact that is endured the initial impacts easy to understand.

The only metal component on the aircraft that was carried a comparable amount of strength to the perimeter columns. While it did destroy some columns, it was a small enough amount that they shifted into the adjacent columns.

It is because of this that the explosion that happened when 90,000 Gallons of jet fuel ignited. The fire following this was the principal cause of the collapse.

Although many people use this as a reason for the collapse, jet fuel doesn’t get as hot as people think and the steel never melted.

The maximum flame temperature increase for burning jet fuel in air is about 1,000°C. That is very far from melting steel at 1,500°C. However the steel did fail

It failed for two reasons, loss of strength due to the temperature of the fire, and loss of structural integrity due to distortion of the steel from the non-uniform temperatures in the fire.

The WTC had a redundant design like many other sky scrapers. But although it is made to “fix” itself, the shifting loads will eventually overstress the adjacent members.

All in all, the world trade center was not defectively designed. It was built to withstand many things but a 90,000 gallon jet fuel caused fire, was not anticipated, and base on the information in this article, the WTC did much better than what would be expected.