Numerous structural engineers now publicly challenge the government's account of the destruction of the Trade Centers on 9/11, including:
Two professors of structural engineering at a prestigious Swiss university (Dr. Joerg Schneider and Dr. Hugo Bachmann) said that, on 9/11, World Trade Center 7 was brought down by controlled demolition (translation here)
Kamal S. Obeid, structural engineer, with a masters degree in Engineering from UC Berkeley, of Fremont, California, says:
"Photos of the steel, evidence about how the buildings collapsed, the unexplainable collapse of WTC 7, evidence of thermite in the debris as well as several other red flags, are quite troubling indications of well planned and controlled demolition"
Ronald H. Brookman, structural engineer, with a masters degree in Engineering from UC Davis, of Novato California, writes:
"Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing the contents into dust and ash - twice. Why would all 47 stories of WTC 7 fall straight down to the ground in about seven seconds the same day? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified for all three collapses including the surviving steel samples and the composition of the dust."
Graham John Inman, structural engineer, of London, England, points out:
"WTC 7 Building could not have collapsed as a result of internal fire and external debris. NO plane hit this building. This is the only case of a steel frame building collapsing through fire in the world. The fire on this building was small & localized therefore what is the cause?"
Paul W. Mason, structural engineer, of Melbourne, Australia, argues:
"In my view, the chances of the three buildings collapsing symmetrically into their own footprint, at freefall speed, by any other means than by controlled demolition, are so remote that there is no other plausible explanation!"
David Scott, Structural Engineer, of Scotland, argues:
"Near-freefall collapse violates laws of physics. Fire induced collapse is not consistent with observed collapse mode . . . ."
Nathan Lomba, Structural Engineer, of Eureka, California, states
"I began having doubts about, so called, official explanations for the collapse of the WTC towers soon after the explanations surfaced. The gnawing question that lingers in my mind is: How did the structures collapse in near symmetrical fashion when the apparent precipitating causes were asymmetrical loading? The collapses defies common logic from an elementary structural engineering perspective. “If” you accept the argument that fire protection covering was damaged to such an extent that structural members in the vicinity of the aircraft impacts were exposed to abnormally high temperatures, and “if” you accept the argument that the temperatures were high enough to weaken the structural framing, that still does not explain the relatively concentric nature of the failures.
Neither of the official precipitating sources for the collapses, namely the burning aircraft, were centered within the floor plan of either tower; both aircraft were off-center when they finally came to rest within the respective buildings. This means that, given the foregoing assumptions, heating and weakening of the structural framing would have been constrained to the immediate vicinity of the burning aircraft. Heat transmission (diffusion) through the steel members would have been irregular owing to differing sizes of the individual members; and, the temperature in the members would have dropped off precipitously the further away the steel was from the flames—just as the handle on a frying pan doesn't get hot at the same rate as the pan on the burner of the stove. These factors would have resulted in the structural framing furthest from the flames remaining intact and possessing its full structural integrity, i.e., strength and stiffness.
Structural steel is highly ductile, when subjected to compression and bending it buckles and bends long before reaching its tensile or shear capacity. Under the given assumptions, “if” the structure in the vicinity of either burning aircraft started to weaken, the superstructure above would begin to lean in the direction of the burning side. The opposite, intact, side of the building would resist toppling until the ultimate capacity of the structure was reached, at which point, a weak-link failure would undoubtedly occur. Nevertheless, the ultimate failure mode would have been a toppling of the upper floors to one side—much like the topping of a tall redwood tree—not a concentric, vertical collapse.
For this reason alone, I rejected the official explanation for the collapse of the WTC towers out of hand. Subsequent evidence supporting controlled, explosive demolition of the two buildings are more in keeping with the observed collapse modalities and only serve to validate my initial misgivings as to the causes for the structural failures."
Edward E. Knesl, civil and structural engineer, of Phoenix, Arizona, writes:
"We design and analyze buildings for the overturning stability to resist the lateral loads with the combination of the gravity loads. Any tall structure failure mode would be a fall over to its side. It is impossible that heavy steel columns could collapse at the fraction of the second within each story and subsequently at each floor below.
We do not know the phenomenon of the high rise building to disintegrate internally faster than the free fall of the debris coming down from the top.
The engineering science and the law of physics simply doesn't know such possibility. Only very sophisticated controlled demolition can achieve such result, eliminating the natural dampening effect of the structural framing huge mass that should normally stop the partial collapse. The pancake theory is a fallacy, telling us that more and more energy would be generated to accelerate the collapse. Where would such energy would be coming from ?"
David Topete, civil and structural engineer, San Francisco, California
Charles Pegelow, structural engineer, of
Houston, Texas (and see this)
Dennis Kollar, structural engineer, of
West Bend, Wisconsin
Doyle Winterton, structural engineer (retired)
Michael T. Donly, P.E.,
structural engineer
William Rice,
P.E., structural engineer, former professor of Vermont Technical College (May
27, 2008)
http://georgewashington2.blogspot.com/2008/05/prominent-structural-engineers-say.html
See this website and this website for further
additions.
There are many other structural engineers who have questioned the government's account in
private. We support them and wish them courage to discuss these vital issues publicly.
See also this.