Numerous structural engineers â" the people who know the most about office building vulnerabilities and accidents â" say that the official explanation of why building 7 at the World Trade Center collapsed on 9/11 is "impossible", "defies common logic" and "violates the law of physics":
- 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)
- Alfred Lee Lopez, with 48 years of experience in all types of buildings:
I agree the fire did not cause the collapse of the three buildings. The most realistic cause of the collapse is that the buildings were imploded
- John D. Pryor, with more than 30 years experience:
The collapse of WTC7 looks like it may have been the result of a controlled demolition. This should have been looked into as part of the original investigation
- Robert F. Marceau, with over 30 years of structural engineering experience:
From videos of the collapse of building 7, the penthouse drops first prior to the collapse, and it can be noted that windows, in a vertical line, near the location of first interior column line are blown out, and reveal smoke from those explosions. This occurs in a vertical line in symmetrical fashion an equal distance in toward the center of the building from each end. When compared to controlled demolitions, one can see the similarities
- Kamal S. Obeid, structural engineer, with a masters degree in Engineering from UC Berkeley and 30 years of engineering experience, 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
- Steven L. Faseler, structural engineer with over 20 years of experience in the design and construction industry:
World Trade Center 7 appears to be a controlled demolition. Buildings do not suddenly fall straight down by accident
- Ronald H. Brookman, structural engineer, with a masters degree in Engineering from UC Davis, writes:
Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing the contents into dust and ash â" 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 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 notes:
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 says:
Near-freefall collapse violates laws of physics. Fire induced collapse is not consistent with observed collapse mode . . .
- Nathan Lomba 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 flamesâ"just as the handle on a frying pan doesnâ(TM)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 sideâ"much like the topping of a tall redwood treeâ"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 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 doesnâ(TM)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?
- Antonio Artha,with 15+ years of experience in building design
Fire and impact were insignificant in all three buildings. Impossible for the three to collapse at free-fall speed. Laws of physics were not suspended on 9/11, unless proven otherwise
The symmetrical "collapse" due to asymmetrical damage is at odds with the principles of structural mechanics
It is virtually impossible for WTC building 7 to collapse as it did with the influence of sporadic fires. This collapse HAD to be planned
- Travis McCoy, M.S. in structural engineering
- James Milton Bruner, Major, U.S. Air Force, instructor and assistant professor in the Deptartment of Engineering Mechanics & Materials, USAF Academy, and a technical writer and editor, Lawrence Livermore National Laboratory
It is very suspicious that fire brought down Building 7 yet the Madrid hotel fire was still standing after 24 hours of fire. This is very suspicious to me because I design buildings for a living
- David Anthony Dorau, practicing structural engineer with 18 yearsâ(TM) experience in the inspection and design of buildings under 5 stories tall, who worked as a policy analyst for the Office of Technology Assessment, an arm of the U.S. Congress providing independent research and reports on technological matters
- Russell T. Connors, designed many buildings and other types of structures
- Lester Jay Germanio, 20+ years experience
- Daniel Metz, 26+ years experience
- Jonathan Smolens, 11 years experience, with a specialty in forensic engineering
- William Rice, P.E., structural engineer, former professor of Vermont Technical College
The above is just a sample. Many other structural engineershave questioned the collapse of Building 7, as have numerous experts in other disciplines, including:
- The former head of the Fire Science Division of the government agency which claims that the World Trade Centers collapsed due to fire (the National Institute of Standards and Technology), who is one of the worldâ(TM)s leading fire science researchers and safety engineers, a Ph.D. in mechanical engineering (Dr. James Quintiere), called for an independent review of the World Trade Center collapse investigation. "I wish that there would be a peer review of this," he said, referring to the NIST investigation. "I think all the records that NIST has assembled should be archived. I would really like to see someone else take a look at what theyâ(TM)ve done; both structurally and from a fire point of view. â¦ I think the official conclusion that NIST arrived at is questionable."
- Harry G. Robinson, III â" Professor and Dean Emeritus, School of Architecture and Design, Howard University. Past President of two major national architectural organizations â" National Architectural Accrediting Board, 1996, and National Council of Architectural Registration Boards, 1992. In 2003 he was awarded the highest honor bestowed by the Washington Chapter of the American Institute of Architects, the Centennial Medal. In 2004 he was awarded the District of Columbia Council of Engineering and Architecture Societies Architect of the Year award. Principal, TRG Consulting Global / Architecture, Urban Design, Planning, Project Strategies. Veteran U.S. Army, awarded the Bronze Star for bravery and the Purple Heart for injuries sustained in Viet Nam â" says:
The collapse was too symmetrical to have been eccentrically generated. The destruction was symmetrically initiated to cause the buildings to implode as they did
- And a prominent physicist with 33 years of service for the Naval Research Laboratory in Washington, DC (Dr. David L. Griscom) said that the official theory for why Building 7 collapsed "does not match the available facts" and supports the theory that the buildings were brought down by controlled demolition