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"...this is the result of something that was planned. It's not accidental that the first tower just happened to collapse, and the second tower just happened to collapse in exactly the same way."

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The "Truss Theory":
A Fantasy Concocted to Conceal a Demolition

According to [WTC designer Leslie Robertson], New York City has some of the worst wind loads in the nation ... This is because of the occasional wind generated off of the Atlantic Ocean during hurricane season. As a result, buildings in New York City must be designed to be twice as strong as similar buildings designed to withstand an earthquake in Los Angeles. [NYC24]

If the above is true then why is it claimed the twin towers were bolted together with non-composite (weak) steel deck trusses? There would be no strength in the structure.

To illustrate the point lets take a close look at two fundamental parts of the official 'truss theory', namely the trusses and bolts...

The WTC trusses (shown above) spanned 60' and 35' between the inner core and perimeter walls.

Here is a floor plan showing the layout of trusses used in the twin towers construction:

A small piece of the plan has been highlighted in red. This is where a truss is attached to the inner core. Details of the inner core:

The core was designed to support the entire weight of the buildings several times over. Far more than a mere "service core", it comprised of 47 steel box columns tied together at each floor by steel plates, similar to the 52" deep spandrel plates that tied the perimeter columns together. The largest of these core columns were 18"x36", with steel walls 4" thick near the base and tapering in thickness toward the top, and was anchored directly to the bedrock.

Photograph showing WTC 1 inner core during construction:

The inner core of WTC 1 was the most solid part of the building.

According to the WTC Report the only thing securing trusses to the inner core and perimeter walls were 5/8" bolts:

A chain is only as strong as it's weakest link, and these permanently stressed bolts would be a very weak link - they'd had 30 years of wear and corrosion - but if the 'truss theory' is to be believed then they were the only things holding the twin towers together.

On 9/11 Flight 11 plowed into WTC 1 at 470 mph, the inner core of the building bore the brunt of the 150+ ton airliner's impact.

'Truss theory' trusses failing

If the 'truss theory' were true then the force of the plane's impact would have knocked the inner core backwards, this would have crushed numerous trusses on the opposite side of the building and sheared off a massive number of truss connecting bolts.

Airliner & debris weight + bolt failures + catastrophic truss failures = immediate "pancake collapse" of all floors (but not the core).

History shows this didn't happen.

Cary Sheih on the 72nd floor of WTC 1 when Flight 11 hit the building:

'I heard a loud explosion, which was immediately followed by tremendous building sways and vibrations. As I was thrown out of my chair, I immediately thought that this was an earthquake, but still thinking rationally, I thought that it was abnormal since there are no earthquakes in NYC, especially of this magnitude. I remember thinking that the building felt like it was going to collapse from this initial explosion.' [TruthOrFiction]

WTC 1 shook and swayed so violently that it threw Cary Sheih from his chair, but it remained standing. This is incredible, especially when you consider the following collapse study:

Weak single bolts 'contributed to WTC collapse'

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]

If the building was truly held together by weak bolts then the single bolt connections should have "popped and fell apart" when Flight 11 smashed into the inner core of WTC 1, not 1½ hours after the event.

The following photo shows Flight 11's impact area in WTC 1.

A closer look shows straight edges where the trusses held the perimeter wall rigid.

If the trusses were weak the entire area of the perimeter wall where the plane hit would have bent inwards as trusses were crushed upon impact. You would not see a plane shaped hole in an otherwise flat wall.

The total weight of the structure was roughly 500,000 t, but wind load, rather than the gravity load, dominated the design. The building is a huge sail that must resist a 225 km/h hurricane. It was designed to resist a wind load of 2 kPa—a total of lateral load of 5,000 t. [tms.org]

Below is an unscaled schematic of the proposed WTC trusses and their attachment to columns.

The WTC buildings could sway up to 3 feet in any direction in a strong wind. It is implausible to suggest the above design could effectively transfer 5,000 t of lateral load to the core. The photo of the coal mine dredge on this page gives you an example of 5,000 t. Trusses would be crushed and bolts sheared off.

The only way WTC 1 could have withstood the wind load and survived Flight 11's impact is if the building was solidly constructed. The following from the BBC shows a far more solid structure and reveals how loading was transferred from the perimeter walls to the core.

At the heart of the structure was a vertical steel and concrete core, housing lift shafts and stairwells.

Steel beams radiate outwards and connect with steel uprights, forming the building's outer wall.

All the steel was covered in concrete to guarantee firefighters a minimum period of one or two hours in which they could operate - although aviation fuel would have driven the fire to higher-than-normal temperatures.

[BBC News 9/13/2001]

Proof of the buildings' solid structure lies in the fact they stood for thirty years in winds which sometimes reached hurricane force. Would ¼ mile high buildings which relied solely on the integrity of weak trusses and 5/8" bolts have stood for thirty years?

"The building was designed to have a fully loaded 707 crash into it, that was the largest plane at the time. I believe that the building could probably sustain multiple impacts of jet liners because this structure is like the mosquito netting on your screen door - this intense grid - and the plane is just a pencil puncturing that screen netting. It really does nothing to the screen netting."


Frank A. Demartini, on-site construction
manager for the World Trade Center

Update:

In 2006 NIST revised the "truss theory" because it did not withstand scrutiny.

In the revised "sagging truss theory" the WTC floor truss system has changed. The image below shows the revised system.

We now see that bridging trusses have been added to give more strength to the structure.

How did NIST overlook these in their original theory?

NIST is now stating sagging trusses pulled the perimeter walls inwards until they explosively failed:

On the one hand we are being told that the steel of the trusses was weakened by the heat of fires, and on the other hand we are being told that this weakened steel was strong enough to pull the perimeter walls inwards until the structure failed.

This is self-contradicting nonsense.

Also, the 5/8" bolts would have failed long before the perimeter walls.

To illustrate this point the left figure below shows a perimeter wall column section from the upper part of the towers, where the steel was thinnest, and the right figure shows a section from a column in the lower part of the towers, where the steel was much thicker.

The following image gives an idea of the scale of the perimeter wall in comparison to a 5/8" bolt.

It is laughable to suggest that 5/8" bolts which did not properly secure the towers' steel floor trusses could pull the perimeter walls inwards until they explosively failed.

When Flight 11 flew into WTC 1, one of two things should have happened:

  1. If the building had nothing more than steel trusses bolted between the inner core and perimeter walls there should have been an immediate "pancake collapse" of all floors (but the core should have remained intact).

  2. If the building was solidly constructed it should have remained standing.

Neither of the above occurred.

The "truss theory" is a fantasy concocted to conceal a demolition.


See also:

So what happens when World Trade Center type trusses are heated?
The 9/11 WTC Collapses: An Audio-Video Analysis


What Really Happened