Essay: How the World Trade Center Collapsed
There are suggestions that the resultant temperatures led to the melting of the steel making the building structure. However, according to scientific research hydrocarbons burn to maximum of 1100 degrees Celsius where as the melting point of steel is 1500 degrees Celsius. This is a proof that the steel bars could not have melted because of the fire of the jet fuels. It is understood that the Underwriters Laboratories (UL) had certified that the steel used for building WTC could withstand such heat for a period of six hours but this is a lie.
When exposed steel is heat to high temperatures, of more than 1000 degrees Celsius, it softens and loses its strength up to eight times and because of this, it cannot withstand the weight it is supposed to carry at room temperature. This is why the floors started to sag in as the temperatures increased and thus the supporting columns started to be pulled in. (Iron and Steel Institute 1998 pp 123-155) The impact damaged the piping system, and thus there was no water to put out the fire. Survivors said that there was water on the staircases but this was from the piping since it ran along the staircases. The thick dark smoke from the burning building was caused by lack of oxygen. The large amounts of jet fuel present in the building led to excessive burning which resulted to depleted levels of oxygen. A fire, without enough supply of oxygen is characterized by thick smoke and soot and this was the case then.