What Caused the Core of WTC 1 to Fail?

We are told that WTC 1 collapsed because the core of the building failed:

The 767 had smashed through the outer wall and hit the inner core directly destroying the fire protection. The intense fire that followed had then concentrated around the core. Two things would then have happened. Floor trusses, softened by the fire, would have fallen away from the core. Without the trusses to hold it firm, the core would have lost crucial support. At the same time, the core’s exposed steel girders, also long softened by the heat, would have begun to buckle under the weight of the tower. The result: another progressive collapse. [BBC Horizon]

The massive core of the World Trade Center - click for full sized image

< The Windsor Building fire - [Full details]

The core of the structurally similar Windsor Building in Madrid withstood an 800°C inferno for more than 18 hours without failing, and since no 800°C inferno existed in WTC 1 it is impossible to believe that heat caused the core of this building to fail.

Woman waving from WTC 1 impact area - [Full details] >

This 2.6 MB WMV video of WTC 1 was shot from a tripod and gives a clear perspective the collapse. It can be viewed frame by frame with this software (free demo). Gamma correction has been applied to the two video frames shown below to clarify the images.

Frame 0 shows the building immediately prior to the collapse, frame 42 shows the building ~1½ seconds later:

Frame 0 - one frame before collapse.

Frame 42 - forty one frames into collapse.

The reduction in the height of the mast indicates the core of WTC 1 has failed. The height reduction also indicates the core has fallen further than the perimeter walls.

The single-bolt connections in the framework of the World Trade Center popped and fell apart during the September 11 terrorist attacks, causing the floors to collapse on top of each other, according to a new study. The analysis, conducted by a team of researchers from the Massachusetts Institute of Technology (MIT), concludes the bolts did not properly secure the towers' steel floor trusses, The New York Post reported yesterday. [CBS News]

Details of floor trusses & bolts

If the 'truss theory' and the above MIT study were true then all of the single bolt connections above the aircraft impact level would have "popped and fell apart" the moment the core dropped - the descending core would have sheared off all bolts connecting trusses to the inner core. This would have resulted in the simultaneous failure of all trusses in and around the highlighted section of the building, and the perimeter walls would have lost all support.

"Truss theory" trusses failing

The perimeter walls were not designed to be load bearing and would have had little strength without the bracing of trusses, therefore the top section of WTC 1 should have visually disintegrated as the roof came down.

The video shows no disintegration in the top section of WTC 1 as it comes down - the structure is visually solid. It is obvious that WTC 1's structure was nowhere near as weak as we are led to believe.

Televised images of the attacks on the World Trade Center suggest that explosives devices caused the collapse of both towers, a New Mexico Tech explosion expert said Tuesday. The collapse of the buildings appears "too methodical" to be a chance result of airplanes colliding with the structures, said Van Romero, vice president for research at New Mexico Institute of Mining and Technology.

"My opinion is, based on the videotapes, that after the airplanes hit the World Trade Center there were some explosive devices inside the buildings that caused the towers to collapse," Romero said. Romero is a former director of the Energetic Materials Research and Testing Center at Tech, which studies explosive materials and the effects of explosions on buildings, aircraft and other structures. [Albuquerque Journal 9/14/2001]

The above video indicates Romero's 9/14/2001 assessment of the collapses was fundamentally sound. Falling bodies never take the path of greatest resistance - without exception they always take the path of least resistance. If fires somehow managed to weaken the core columns of WTC 1 to the point of failure then the top of the building would have fallen to the side. It didn't - it fell straight downwards indicating the path of least resistance was through the lower portion of the building.

WTC 1's vertical collapse is consistent with a demolition which utilises shaped charges to destroy the core columns of the building.

How could explosives have been planted in the World Trade Center?

Ask Marvin Bush.