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The Structural Engineering Community Rejects the Controlled-Demolition Conspiracy Theory
The structural engineering community rejects the controlled-demolition conspiracy theory. Its consensus is that the collapse of the World Trade Center buildings was a fire-induced, gravity-driven collapse, an explanation that does not involve the use of explosives.
Civil & Structural Engineers on WTC Collapse
"The aircraft moved through the building as if it were a hot and fast lava flow," Sozen says. "Consequently, much of the fireproofing insulation was ripped off the structure. Even if all of the columns and girders had survived the impact - an unlikely event - the structure would fail as the result of a buckling of the columns.
The heat from an ordinary office fire would suffice to soften and weaken the unprotected steel. Evaluation of the effects of the fire on the core column structure, with the insulation removed by the impact, showed that collapse would follow whatever the number of columns cut at the time of the impact."
911-engineers.blogspot.com...
Critical analysis of the collapse of wtc towers 1, 2 & 7
www.jod911.com...
What have we learned from 9-11 that can be used to prevent future large-scale terrorist attacks in the U.S.A.?
Evolution of Building Code Requirements in a Post 9/11 World
www.ctbuh.org...
Whatever it is they're saying, what I am saying is that it's ridiculous that NIST not releasing their modelling data is somehow acceptable.
(NIST) Federal Building and Fire Safety Investigation of the World Trade Center Disaster
Some 200 technical experts—including about 85 career NIST experts and 125 leading experts from the private sector and academia—reviewed tens of thousands of documents, interviewed more than 1,000 people, reviewed 7,000 segments of video footage and 7,000 photographs, analyzed 236 pieces of steel from the wreckage, performed laboratory tests and sophisticated computer simulations of the sequence of events that occurred from the moment the aircraft struck the towers until they began to collapse.
www.webcitation.org...
Do they actually publish their data publicly and have it peer-reviewed, unlike NIST?
You know why it's impossible to show proof of explosives? Because almost all of the wreckage was shipped to India or China and melted down.
Pretty much no one was allowed to look at it. Not even FEMA. All the trucks carrying the wreckage from G-0 were expensively outfitted with GPS tracking devices. The US government really wanted to sell that steel to China at... Er, below average prices.
THE COLLAPSE
Nearly every large building has a redundant design that allows for loss of one primary structural member, such as a column. However, when multiple members fail, the shifting loads eventually overstress the adjacent members and the collapse occurs like a row of dominoes falling down.
The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t.
As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. This started the domino effect that caused the buildings to collapse within ten seconds, hitting bottom with an estimated speed of 200 km per hour. If it had been free fall, with no restraint, the collapse would have only taken eight seconds and would have impacted at 300 km/h.1 It has been suggested that it was fortunate that the WTC did not tip over onto other buildings surrounding the area. There are several points that should be made. First, the building is not solid; it is 95 percent air and, hence, can implode onto itself. Second, there is no lateral load, even the impact of a speeding aircraft, which is sufficient to move the center of gravity one hundred feet to the side such that it is not within the base footprint of the structure. Third, given the near free-fall collapse, there was insufficient time for portions to attain significant lateral velocity.
To summarize all of these points, a 500,000 t structure has too much inertia to fall in any direction other than nearly straight down.
www.tms.org...
Not even FEMA.
a reply to: samkent
FEMA doesn't investigate building collapses. Where did you get the idea that they did?
Pretty much no one was allowed to look at it. Not even FEMA.
Some 200 technical experts—including about 85 career NIST experts and 125 leading experts from the private sector and academia
analyzed 236 pieces of steel from the wreckage, performed laboratory tests, and created sophisticated computer simulations of the sequence of events that occurred from the moment the aircraft struck the towers until they began to collapse.
analyzed 236 pieces of steel from the wreckage, performed laboratory tests, and created sophisticated computer simulations of the sequence of events that occurred from the moment the aircraft struck the towers until they began to collapse.