Posted on 09/11/2023 12:41:34 PM PDT by nickcarraway
Countless conspiracy theories have circulated in the wake of 9/11, the day when terrorists hijacked planes and attacked the World Trade Center in New York twenty two years ago.
By David Oswald, RMIT University; Erica Kuligowski, RMIT University, and Kate Nguyen, RMIT University
The collapse of the World Trade Center has been subject to intense public scrutiny over the twenty years since the center’s Twin Towers were struck by aircraft hijacked by terrorists. Both collapsed within two hours of impact, prompting several investigations and spawning a variety of conspiracy theories.
Construction on the World Trade Center 1 (the North Tower) and World Trade Center 2 (the South Tower) began in the 1960s. They were constructed from steel and concrete, using a design that was groundbreaking at the time. Most high-rise buildings since have used a similar structure.
The investigatory reports into the events of September 11, 2001 were undertaken by the US Federal Emergency Management Agency (FEMA) and the National Institute of Standards and Technology.
Grecian Delight supports Greece FEMA’s report was published in 2002. This was followed by the National Institute of Standards and Technology’s three-year investigation, funded by the US Federal Government and published in 2005.
Some conspiracy theorists seized on the fact the NIST investigation was funded by the federal government, believing the government itself had caused the twin towers’ collapse or was aware it would happen and deliberately didn’t act.
While there have been critics of both reports (and the investigations behind them weren’t flawless), their explanation for the buildings’ collapse is widely accepted. They conclude it was not caused by direct impact by the aircraft or the use of explosives but by fires that burned inside the buildings after impact.
Why did the towers collapse as they did on 9/11? Some have questioned why the buildings did not “topple over” after being struck side-on by aircraft. But the answer becomes clear once you consider the details.
Aircraft are made of lightweight materials, such as aluminium. If you compare the mass of an aircraft with that of a skyscraper more than four hundred meters tall and built from steel and concrete, it makes sense the building would not topple over.
The towers would have been more than one thousand times the mass of the aircraft and designed to resist steady wind loads more than thirty times the aircrafts’ weight.
That said, the aircraft did dislodge fireproofing material within the towers, which was coated on the steel columns and on the steel floor trusses (underneath the concrete slab). The lack of fireproofing left the steel unprotected.
As such, the impact also structurally damaged the supporting steel columns. When a few columns become damaged, the load they carry is transferred to other columns. This is why both towers withstood the initial impacts and didn’t collapse immediately.
Progressive collapse vs 9/11 conspiracy theories This fact also spawned one of the most common conspiracy theories surrounding 9/11: that a bomb or explosives must have been detonated somewhere within the buildings.
These theories have developed from video footage showing the towers rapidly collapsing downwards some time after impact, similar to a controlled demolition. But it is possible for them to have collapsed this way without explosives.
It was fire that caused this, and this fire is believed to have stemmed from the burning of remaining aircraft fuel.
According to the FEMA report, fire within the buildings caused thermal expansion of the floors in a horizontal and outwards direction, pushing against the rigid steel columns, which then deflected to an extent but resisted further movement.
9/11 conspiracy theories This figure shows the expansion of floor slabs and framing which likely happened as a result of the fires. Credit: FEMA With the columns resisting movement, there was nowhere else for the concrete floors to expand. This led to an increased buildup of stress in the sagging floors until the floor framing and connections gave in.
The floors’ failure pulled the columns back inwards, eventually leading to their buckling and the floors collapsing. The collapsing floors then fell on more floors below, leading to a progressive collapse.
9/11 conspiracy theories The buckling of columns initiated by floor failure. Credit: FEMA This explanation, documented in the official reports, is widely accepted by experts as the cause of the Twin Towers’ collapse. It is understood the South Tower collapsed sooner because it suffered more damage from the initial aircraft impact, which also dislodged more fireproofing material.
The debris from the collapse of the North Tower set at least ten floors alight in the nearby World Trade Center 7, or “Building 7,” which also collapsed about seven hours later.
While there are different theories regarding how the progressive collapse of Building 7 was initiated, there is consensus among investigators that fire was the primary cause of failure.
Both official reports made a range of fire safety recommendations for other high-rise buildings, including the improvement of evacuation and emergency response. In 2007, the National Institute of Standards and Technology also published a best practice guide recommending risk-reducing solutions for progressive collapse.
What does this mean for high-rise buildings? Before 9/11, progressive collapse was not well understood by engineers. The disaster highlighted the importance of having a “global view” of fire safety for a building, as opposed to focusing on individual elements.
There have since been changes to building codes and standards on improving the structural performance of buildings on fire, as well as opportunities to escape (such as added stairwell requirements).
At the same time, the collapse of the Twin Towers demonstrated the very real dangers of fire in high-rise buildings. In the decades since the World Trade Center was designed, buildings have become taller and more complex, as societies demand sustainable and cost-effective housing in large cities.
Some eighty-six of the current one hundred tallest buildings in the world were built since 9/11. This has coincided with a significant increase in building façade fires globally, which have gone up sevenfold over the past three decades.
This increase can be partly attributed to the wide use of flammable cladding. It is marketed as an innovative, cost-effective, and sustainable material; yet, it has shown significant shortcomings in terms of fire safety, as witnessed in the 2017 Grenfell Disaster.
The Grenfell fire (and similar cladding fires) are proof fire safety in tall buildings is still a problem, and as structures get taller and more complex with new and innovative designs and materials, questions around fire safety will only become more difficult to answer.
The events of 9/11 may have been challenging to foresee, but the fires that led to the towers’ collapse could have been better prepared for.The Conversation
David Oswald, Senior Lecturer in Construction, RMIT University; Erica Kuligowski, Vice-Chancellor’s Senior Research Fellow, RMIT University, and Kate Nguyen, Senior Lecturer, ARC DECRA Fellow and Victoria Fellow, RMIT University
The only one real evidence that we have that the planes were hijacked was Flight 93, where they actually had a phone call from one of the passengers stating that they have been hijacked and the passengers are going to try to take back the plane.
Everything else is possibly manipulated if we didn’t have that one evidence.
We should know by now that what it means when something is “debunked”
Debunking COVID-19 myths
6 conspiracy theories about the 2020 election – debunked
https://www.cbsnews.com/news/presidential-election-2020-conspiracy-theories-debunked/
Jan. 6 Committee staffer debunks the Ray Epps conspiracy theory
https://www.cbsnews.com/video/jan-6-committee-staffer-debunks-the-ray-epps-conspiracy-theory/
The conspiracy theory is that a bunch of rag heads flew airliners into the twin towers and made them collapse. I can’t find anybody I personally know who still believes it.
GG2, you CAN’T be right.
I saw it all on TV!!!
In the improbable case that any explosives were planted in WTC7 or the other buildings before the plane impacts, they were most likely planted by the terrorists.
“The conspiracy theory is that a bunch of rag heads flew airliners into the twin towers and made them collapse. I can’t find anybody I personally know who still believes it.”
^^^^^^^^^^^that^^^^^^^^^^^^
Nobody will so much as look at any of them seriously unless they in their heart want to see the US disgraced in the first place (so consider the source).
Yes I totally watched a commercial airliner hit and disappear into a steel building and the nose of it burst out the other side. The most unbelievable thing I’ve ever seen. Emphasis on unbelievable. 😏
Discussing 9/11/01 without mentioning islam or muslims is like memorializing the Pearl Harbor attack without blaming Japs.
‘Eff barbaric islam.
There was no conspiracy to take down the twin towers and attack the Pentagon? How so? Did the hijackers hold a news conference announcing their intentions?
Have the words “conspiracy theorist” been redefined as simply holding unapproved views? For example: Conspiracy theorists think that Hillary Clinton’s repeated references to a “vast right-wing conspiracy” make her conspiracy theorist.
The Onion is SO thick with so many layers, I’m always open to it, and always learning more. Breathtaking!
Have you seen the GWB plane-hit-steel reading lesson extended? The teacher goes *right into* the book ‘Pet Goat’. You’ve seen the animated ‘Pet Goat 2’, right? I always wondered if there were a ‘Pet Goat 1’, and apparently there is - it is the book form.
Agreed. Terrorists like those employed by the CIA and MOSSAD.
Bad welds on the brackets holding up the floor trusses.
[Plus no physical interference between the brackets and at least the outer wall columns. All the loads were on the welds.]
Just watched over week-end 9/11 documentary. There was a stewardess on one of the other planes that hit the towers and she said that it was a highjack, two men entered the cockpit, one person was stabbed. It’s on audio of her call to 911.
I listened to the radio all day.
An announcer said a fighter jet shot a passenger jet down
Anyone else hear that?
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