Why the World Trade Centres Collapsed.
The building was unique in design in that it was meant to have as much floor space as possible with minimal interior building structure as possible. The outside walls were to be made with steel core and aluminum framing. These walls would have small openings (relative to its size) but the outside walls would extend about two floors and would be attached by plates. Each floor was to have light weight floors that were of steel construction and with poured concrete on the surface. Each floor would be attached to the outside walls to provide the structural support and with the core of the building that would supply the elevators, air shafts and additional structural support in the form of steel columns that ran from the bedrock to the top of the building.
|WTC under construction|
|The cranes used to raise construction equipment to the working floors would be built into the columns as you can see in the picture.|
|Bird cage construction and design can be clearly seen in this photo|
|Fortune Tower, Dubai (did not collapse) on fire notice the heavy concrete and rebar construction as opposed to the light weight steel frame construction of the WTC.|
|The large office space requested by the design meant that the outside walls would be integral to the structure of the building. But as can be easily seen in this picture the floors themselves were never meant to have large amounts of weight placed or even worse dropped on them.|
The steel outer walls need not break or buckle all that needs to occur is for the small brackets to collapse/ warp/ or bend thus releasing the weight of the floor onto the next floor beneath it.
|Parts of the outer wall can be seen in the rubble pile|
|Heat signatures by thermal camera on Sept 16, which is the molten metal|
|Molten metal found at the site days into the rescue/ deconstruction (note dust plume).|
What of thermite found at the site?
|Thermite found at the site|
Thermite is a pyrotechnic composition of a metal powder and a metal oxide, which produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminum is the reducing agent it is called an aluminothermic reaction. The floors and structure were made of steel that had been exposed to high stress loads, salt air and time. This in itself produces Iron oxide. Aluminum comes from the casing and the many components that make up a modern office building as well as 175 000 lbs of aircraft (767 dry weight) all made from high grade aluminum roughly 5 mm thick. Thermite can also be found all across the site as the methods of rescue and deconstruction allowed much dust and debris to invade all levels of the site.
|Note thermite dust and smoke and note the angle cuts made by the Iron worker.|
|Cutting the girders.|
Any sounds of explosions was the millions of pounds of jet fuel burning at different rates (as some fell down elevator shafts), diesel fuel (as in the case of WTC7) the sound of bodies as they hit the pavement and from a distance can sound like explosions as well as office equipment, computer screens transformers and other combustible material.
Finally I will end this today with the myth of free fall.
Many believe that there was a complete free fall speed in the collapse of the WTC. In fact free fall from 110 stories to ground is approximately 9 seconds and WTC 2 collapsed in 11.5 seconds and WTC 1 12.5 seconds. The actual fall times can not be accurately determined as the dust cloud obscures the event. That being said there are still debris falling at between 11 and 12 seconds, not free fall speed.
The WTC towers fell to a combination of luck by the terrorists organizing the attack, good planning, the construction and design of the two buildings. No new report needed, no new investigation just accept the science of it and logic will lead the way.