Controlled demolition

See also: Collapse of the World Trade Center - for images, information about the collapse, and the investigations

Many 9/11 conspiracy theories center on the idea that the World Trade Center collapsed from controlled demolition. The collapse of the World Trade Center was the subject of a multi-year investigation, led by NIST.

Melting steel? · Empire State Building, 1945 B-25 bomber crash · 1975 World Trade Center fire · Free fall? · Explosions? · Material quickly sent for recycling before being examined? · Weekend power down · Molten metal

Controlled demolition?

Fact

• The collapse of the World Trade Center twin towers initiated where the planes hit the buildings. Controlled demolitions always are initiated at the bottom of a building, to take advantage of maximum gravity forces.

• If the World Trade Center collapsed due to controlled demolition, as the theory goes, the explosive charges would have had to survive the crash of airplanes into the buildings. (at ~500 miles per hour)

• When a controlled demolition occurs, you hear the very loud and very distinct sound of the charges going off. These will repeatedly go off, in a quick, regular pattern, for 10+ seconds prior to the structure collapsing. While some people heard what "sounded like an explosion" at the World Trade Center, this is not what they heard or described. Nor is any such sound of demolition charges going off heard in any videos of the collapse.

• The detonations in a controlled demolition go off in a very regular pattern, not at all like the random squibs seen on 9/11. Those squibs are the result of pockets of air (the building is ~70% air in volume) being collapsed, with pulverized gypsum (drywall) and other material being forced out.

• Blasting caps, detonating cord, and other such evidence were not found in the World Trade Center debris.

Here's an actual controlled demolition

This is the June 2006 controlled demolition of an apartment building in Arlington, Virginia.

In the video, notice the very loud sound of demolition charges going off for so many seconds before the entire structure imploded. The collapse of the World Trade Center looks and sounds nothing like this.

Other videos:

• Implosion of the Landmark Tower - Fort Worth, Texas (March 2006)

Melting steel?

The claim that the fires had to be hot enough to melt steel, in order for the buildings to collapse is also false. The fires only need to be hot enough to weaken the steel, causing it to loose structural strength, and deform. Fireproofing that was blown off the columns with the impact of the airplanes made the steel columns all the more susceptible to the heat. Fires in the World Trade Center burned at temperatures as high as 1,100°, which is more than sufficient to cause structural failure and collapse.

Furthermore, since the aircrafts sliced through numerous of the support columns, vastly fewer columns remained to support the load (weight of above floors). The combination of added load and weakened steel, eventually caused the steel columns to fail. At the point of impact (from the aircraft), the floors above began to collapse, with the amount of mass (debris) above the initiation point so large, the force so strong, that nothing beneath it (the structure) could resist it. Thus, the entire collapse.

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Empire State Building, 1945 B-25 bomber crash

Fact

The B-25 bomber crash inflicted relatively light damage to the building.

The size of a B-25 bomber is much smaller than a Boeing 767, with smaller wingspan and smaller fuel capacity. A B-25 bomber has a wingspan of 67 feet, compared with 156 feet for a Boeing 767. The fuel capacity of the B-25 bomber was 1,000 gallons, as compared with 24,000 gallons for a Boeing 767. As well, the speed at which a B-25 bomber travelled was far less than the ~500 mph than the speed that the two Boeing 767's were travelling when they hit the World Trade Center.

The World Trade Center was designed to withstand the force from the impact of a Boeing 707, lost in the fog and travelling at a relatively slow speed of 180 miles per hour.

The Boeing 767 aircraft that hit the World Trade Center were significantly heavier, with fuel for transcontinental flights. American Airlines Flight 11 was travelling at 470 miles per hour when it crashed into the North Tower at 8:46 a.m. United Airlines Flight 175 was travelling at 590 miles per hour when it crashed into the South Tower.

The energy contained in an airplane or other moving object is proportional to the velocity.

where m is the object's mass (in kg) and v is the object's speed (in m·s⁻¹).

Aircraft	Boeing 767 - North Tower	Boeing 767 - South Tower	Boeing 707
Calculation	(179,168 kg * 210.12)/2	(179,168 kg * 263.72)/2	(163,293 kg * 80.46722)/2
Energy	3,954,417,824	6,229,464,421	528,658,660

The engineers also did not consider how fires resulting from a crash would affect the buildings. It was a combination of the damage from the impact of the Boeing 767's, and the resulting fires that ultimately caused the steel columns to weaken to the point where they failed and the building collapsed.

Matthys Levy, an architect at Weidlinger Associates and the author of "Why Buildings Fall Down" (Norton, 1992), watched the first tower collapse while standing at Seventh Avenue and Houston Street, some 20 blocks away. "I saw the beginning of the top moving down, and the whole thing collapsed in a cloud of smoke," Mr. Levy said. "From what I saw, it seemed to come straight down." Mr. Levy said the situation was much different from the one that occurred in 1945 when a much smaller plane slammed into the Empire State Building. That plane, a bomber with a smaller impact and less fuel, ripped a 20-foot hole in the structure, but the building remained standing.^[1]

But Anthony G. Cracchiolo, director of priority capital programs for the Port Authority of New York and New Jersey, which owned the buildings, said little thought had been given to the possibility of a plane crash into the towers. "We never were asked to consider trying to protect the building from such a threat," said Mr. Cracchiolo, who was among those who coordinated the reconstruction after the 1993 bombing. "As structural engineers, there is nothing we could have done to protect the building from a direct impact from a plane as large as these."^[1] Melvin Schweitzer, a member of the Port Authority board of commissioners from 1993 to 1999, said, however, that the board repeatedly inquired about that possibility. "We were just told that architects had explained that the building was designed to withstand a jet," Mr. Schweitzer said. "Frankly, when we raised that question, most of us were thinking of a small plane."^[1]

• B-25 Empire State Building Collision - aerospaceweb.org

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1975 World Trade Center Fire

Fact

Implying that windows were not broken by fires and resulting heat on 9/11, thereby indicating temperature of fire, is illogical. The windows were already broken (by the aircraft impact)! There was nothing more for the fires and heat to break, by the time the fires engulfed the many floors of the WTC buildings.

• Also, why 700°C is required to break windows?
• The New York Times articles about the fire never mentions temperatures, yet along 700°C.

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Free fall?

Fact

A video taken of the collapse shows at 11 seconds that the collapse of the South Tower is still under way. The cameraman began running at that point, but the sound of the building collapsing continues for many more seconds.

The elapsed times for the first exterior panels to strike the ground after the collapse initiated was 11 seconds for 1 WTC (North Tower) and 9 seconds for 2 WTC (South Tower). NIST also points out that significant portions of the cores of both buildings (roughly 60 stories of 1 WTC and 40 stories of 2 WTC) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse.

"The buildings are 70 percent just air in volume and all of the columns are not solid steel, they are steel boxes in which the thickness of the steel varies from 1/4 inch (at the top) to 1 1/2 inches (at the bottom). But they were properly designed to carry the weight of the steel itself, the weight of the partitions, the occupants, the furnishings... those are all things that the structure can withstand very well, but they are not designed to accommodate the failure of a 20 floor section in a dynamic impact on the structure below. If it's moving down in a dynamic fashion, the magnitude of the energy unleashed is so large that no structure can withstand that kind of force that is applied, and the building came down in essentially free fall." -- S. Shyam Sunder

Bazant and Zhou explain that once the collapse initiated on the one floor, the kinetic energy of the top part of the tower impacting on the floor beneath was 8.4 times larger than the plastic energy absorption capability. At that point, the subsequent progressive collapse was inevitable. The amount of resistance or absorption capability that each floor beneath could provide was minuscule in comparison to the amount of kinetic energy from the above structure collapsing. This explains why the collapse happened as quick as it did -- not free fall speed, but perhaps twice the amount of time than free fall.^[2]

• NIST FAQ regarding "free fall"
• Freefall video evidence
• 9/11 Conspiracy Theories - PBS video, with S. Shyam Sunder

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Explosions?

Mike Pecoraro

Those accounts include those of Mike Pecoraro, who worked in the 6th sub-basement level of One World Trade Center.

He recalls:

"They got us again," Mike told his co-worker, referring to the terrorist attack at the center in 1993. Having been through that bombing, Mike recalled seeing similar things happen to the building's structure. He was convinced a bomb had gone off in the building." [2]

Being in the 6th sub-basement level, it's entirely likely that he did not see the airplanes crash into the buildings, and the only thing he could conceive of or compare the situation to was the 1993 bombing.

Pecoraro also "smelled kerosene", which is what jet fuel consists of. [3] It's likely that some jet fuel poured down utility shafts and cause explosions and fires on lower levels of the World Trade Center.

What does a controlled demolition really sound like?

Another critical difference between the collapse of the World Trade Center (and Building 7) and actual controlled demolition is how they sound. Sure, there are some firefighter quotes that mention explosions. These quotes are often taken out of context, and simply explain what it sounded like. These "explosion" sounds could have been all sorts of things, such as elevators crashing down the shafts, and there are also quotes from firefighters where they say the people jumping from the buildings and crashing to the ground "sounded like explosions", not to mention debris that rained down, and the initial plane impacts.

"One gentleman on the 59th floor of the North Tower was ordering food in the cafeteria. That's when he 'heard the explosion' and thought that it was the kitchen oven. He heard that other people said they don't know what it is but it's time to evacuate." -- Oral testimony of Glenn Asaeda, EMS Deputy Medical Director

Jody Bell, of EMS Battalion 4, described the crash of United Airlines Flight 175, "We then hear this explosion. We hear this explosion, and our first reaction is the plane was lodged in the building and it exploded or parts of it were still in the building and that exploded. Then people were screaming that another plane hit."

When people say they "heard explosions" or it "sounded like an explosion", it does not necessarily mean a "bomb exploded". There are numerous other, more likely explanations.

Now, when an actual controlled demolition occurs, the sound of the charges going off is a very distinct sound. They are extremely loud (cannot possibly be missed) and heard repeatedly for numerous seconds. In the demolition (See video) of the Tencza Apartments, a 12 story building, the charges went off for 10 seconds before the building started to collapse. That sound was not heard on 9/11, when the twin towers collapsed, nor when 7 World Trade Center collapsed. It's not heard in any videos, nor heard by eyewitnesses.

Logistics?

Conspiracy theorists are short on explanations as to how explosives could have been planted in the World Trade Center, which were occupied by companies involved in the global 24 x 7 marketplace.

The demolition theory has managed to endure what would seem to be enormous obstacles to its practicality. Controlled demolition is done from the bottom of buildings, not the top, to take advantage of gravity, and there is little dispute that the collapse of the two towers began high in the towers, in the areas where the airplanes struck.

Moreover, a demolition project would have required the tower walls to be opened on dozens of floors, followed by the insertion of thousands of pounds of explosives, fuses and ignition mechanisms, all sneaked past the security stations, inside hundreds of feet of walls on all four faces of both buildings. Then the walls presumably would have been closed up.

All this would have had to take place without attracting the notice of any of the thousands of tenants and workers in either building; no witness has ever reported such activity. Then on the morning of Sept. 11, the demolition explosives would have had to withstand the impacts of the airplanes, since the collapse did not begin for 57 minutes in one tower, and 102 minutes in the other.^[3]

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Material quickly sent for recycling before being examined?

Dr. W. Gene Corley and the rest of the FEMA/ASCE investigation team gained full access to the World Trade Center site, on September 29, 2001. The team also had access to the Fresh Kills Landfill on Staten Island, where they examined structural debris. The team also examined steel and debris at two recycling yards in New Jersey. They obtained samples of the structural steel, which were subjected to laboratory analysis. Numerous other professional engineers (members of SEAoNY) continued this work through Spring 2002, visiting recycling yards and landfills regularly to examine debris and obtain more samples. Additional samples were obtained and sent to NIST, for further study and analysis. While others have expressed some concern that the work of the team was hampered because debris was removed from the site and was subsequently processed for recycling, that was not the case. The team had full access to scrap yards and to the site, and was able to obtain numerous samples. There is no indication that having access to each piece of steel from the World Trade Center would make a significant difference to understanding the performance of the structures.^[4]

Aside from the FEMA/ASCE team, other structural engineering experts were also allowed access to the site to examine steel. Dr. Abdolhassan Astaneh-Asl, of the U.C. Berkeley Department of Civil and Environmental Engineering, arrived one week after 9/11 and started collecting data and investigating structural steel remains. He mapped out the collapsed structure and debris, inspected steel for quality of construction, collected samples for further study, and collected drawings and information on design, construction and maintenance of the buildings. He collected pieces of steel that appeared to be from the impact area, which were later provided to NIST for testing and identification.^[5]

Why was the debris sent to recycling?

• The priority at that time was moving steel out to see if they could find bodies alive or dead. Kenneth Holden, commissioner of the department of design and construction, also said the deal that allows two New Jersey firms to recycle the estimated 310,000 tons of steel from the trade center site would help to recoup at least a tiny part of the original value of the towers and to dispose of the wreckage in an environmentally responsible way. ^[6]

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Weekend power down

How long does it take to prepare for a building implosion?

It takes months to prepare a building for implosion. It's not something that can be done over a weekend.

• The demolition of the Washington DC Convention Center in 2004 involved preparations that went on for months. Massive crews were at work, placing explosives around ~500 columns and doing other preparation work. The crews and activity were highly noticeable to people in the area.^[7]

• The demolition of Kodak Park's Buildings 9 and 23 in Rochester, New York took months of preparation. Setting up the explosives involved cutting torches to slice through metal pipes and heavy equipment to drill holes in the forest of thick concrete support beams, and placing sticks of dynamite into the holes. When they go off, the explosions cause the buildings to implode, or collapse inward.^[8]

Absolutely zero chance that an effort like that could go unnoticed in large office buildings full of workers. Given the nature of stock and bond trading in a global marketplace, with places like Japan, Hong Kong, and London, people were there at all hours. Such preparations would definitely be noticed.

Source of theory

Conspiracy theorists cite two people that worked in the Trade Center for the theory that explosives were placed in the three Trade Center buildings during the weekend before 9/11.

- Ben Fountain was quoted in People Magazine:

• "Ben Fountain, 42, a financial analyst with Fireman's Fund, was coming out of the Chambers Street Station, headed for his office on the 47th floor of the south tower. How could they let this happen? They knew this building was a target. Over the past few weeks we'd been evacuated a number of times, which is unusual. I think they had an inkling something was going on."^[9]

So, the explosives were placed during a number of fire drills? Also, Ben Fountain is only referring to the south tower where he worked. What about the other buildings?

- Conspiracy theorists often cite Scott Forbes, however he is not mentioned or quoted by any mainstream, reliable source on this "power down". His story is not corroborated by anyone else. Forbes was interviewed by Killtown, via e-mail and instant message. [4]

KT: Besides the "power down" the weekend before 9/11, was there any other unusual activity going on related to the WTC? There was one guy, Ben Fountain, who worked on the 47 floor of the WTC 2 who said there was an unusual amount of evacuation drills. Did you experience any of those?

SF: We had regular fire/evacuation drills, but not an unusual number.

KT: Back to the weekend of the "power down," when did they turn the power off and when did they turn it back on?

SF: Off on Saturday afternoon - around 12 noon I think - and back on at about 2 pm on the Sunday (my timings on this are hazy).

About the power down:

KT: Was there a power down in the WTC 1 also?

SF: Not to my knowledge.

SF: I remember that we were notified some 3 or 4 weeks in advance by the Port Authority-NY/NJ that there would be a power outage - so we had to co-ordinate and plan efforts in the IT departments to ensure we had everything shut down in time and ready to restart. Frankly at the time I didn't think about WTC 1.

KT: What did the Port Authority say the power down was for?

SF: As far as I recall it was for re-cabling, though I don't remember the wording on official documents or the detail, as I wasn't in the Management Loop.

The power down occurred above the 48th floor, in order to install new cables to upgrade the computer bandwidth in the building. For security reasons, companies will definitely have staff there during a power down to monitor their servers and equipment.

So, the task of placing explosive, which normally takes much longer, was somehow done during a 26 hour power down on the upper floors of one of the building? What about the other two buildings? There are no reports of a power down in 7 World Trade Center, the other tower, or the bottom 48 floors of the south tower. This scenario is highly unlikely or impossible.

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Molten metal?

Just before 9:52 a.m., a bright spot appeared at the top of a window on the 80th floor of WTC 2, four windows removed from the east edge on the north face, followed by the flow of a glowing liquid. This flow lasted approximately four seconds before subsiding. Many such liquid flows were observed from near this location in the seven minutes leading up to the collapse of this tower. There is no evidence of similar molten liquid pouring out from another location in WTC 2 or from anywhere within WTC 1.

Photographs, and NIST simulations of the aircraft impact, show large piles of debris in the 80th and 81st floors of WTC 2 near the site where the glowing liquid eventually appeared. Much of this debris came from the aircraft itself and from the office furnishings that the aircraft pushed forward as it tunneled to this far end of the building. Large fires developed on these piles shortly after the aircraft impact and continued to burn in the area until the tower collapsed.

NIST concluded that the source of the molten material was aluminum alloys from the aircraft, since these are known to melt between 475 degrees Celsius and 640 degrees Celsius (depending on the particular alloy), well below the expected temperatures (about 1,000 degrees Celsius) in the vicinity of the fires. Aluminum is not expected to ignite at normal fire temperatures and there is no visual indication that the material flowing from the tower was burning.

Pure liquid aluminum would be expected to appear silvery. However, the molten metal was very likely mixed with large amounts of hot, partially burned, solid organic materials (e.g., furniture, carpets, partitions and computers) which can display an orange glow, much like logs burning in a fireplace. The apparent color also would have been affected by slag formation on the surface.^[10]

References

Collapse of the World Trade Center:

• NIST and the World Trade Center
• Answers to Frequently Asked Questions - NIST
• FEMA's World Trade Center Building Performance Study
• Purdue University - 9/11 Attack Simulations Using LS-Dyna (Pentagon and World Trade Center)
• Building on Ground Zero - PBS program
• Impact to Collapse - PBS video, with S. Shyam Sunder of NIST (6 parts)
• 9/11 Conspiracy Theories - PBS video, with S. Shyam Sunder
• Why the World Trade Center Buildings Collapsed - A Fire Chief ’s Assessment, Vincent Dunn (author of the textbook, Collapse of Burning Buildings)
• Why Did the World Trade Center Collapse? Science, Engineering, and Speculation - Thomas W. Eagar and Christopher Musso (JOM, December 2001)
• World Trade Center - Some Engineering Aspects - Tim Wilkinson, University of Sydney
• September 11, 2001 - 9/11 Attack Simulations Using LS-Dyna - Purdue University
• World Trade Center Collapse, Field Investigations and Analyses - Abolhassan Astaneh-Asl, UC-Berkeley
• Dissecting the Collapses - Civil Engineering Magazine, ASCE (May 2002)
• Role of fire resistance issues in the collapse of the Twin Towers - Kodur, V.K.R.
• The World Trade Center Disaster: Analysis and Recommendations - Jeremy Abraham Kirk, MIT.
• Venkatesh Kodur , Ph.D., P.E. - Michigan State University [5]
• Purdue University - Department of Civil Engineering [6]
• Investigating the World Trade Center Collapse: An Update - University of Maryland, Fall 2002

Articles

• Abbout, N., M. Levy, D. Tennant et al (2003) "Anatomy of a Disaster: A Structural Investigation of the World Trade Center collapses", Forensic Engineering.
• Bazant, Z.P., Y. Zhou (2002a) "Why Did the World Trade Center Collapse? - Simple Analysis", Journal of Engineering Mechanics, 128(1), pp. 2-6.
• Bazant, Z.P., Y. Zhou (2002a) "Addendum to: Why Did the World Trade Center Collapse? - Simple Analysis", Journal of Engineering Mechanics, 128(3), pp. 369-370.
• Beyler, C., D. White, M. Peatross et al (2003) "Analysis of the Thermal Exposure in the Impact Areas of the World Trade Center Terrorist Attacks", Forensic Engineering
• Corley, W.G. (2004) "Lessons Learned on Improving Resistance of Buildings to Terrorist Attacks", Journal of Performance of Constructed Facilities, ASCE, Vol 18(2), May 1, 2004, pp. 68-78.
• Why Did the World Trade Center Collapse? - Simple Analysis - Zdenek P. Bazant, and Yong Zhou (Journal of Engineering Mechanics, September 2001)
• Gayle, Frank W; Banovic, Stephen W; Foecke, Tim; Fields, Richard J; Luecke, William E; McColskey, J David; McCowan, Chris; Siewert, Thomas A (October 2004) The structural steel of the World Trade Center towers, Advanced Materials & Processes. Vol. 162, no. 10, pp. 37-39.
• The Towers Lost and Beyond - Eduardo Kausel, MIT Civil Engineering
• Lane, Barbara (2003) "Letter to the Editor", Fire Safety Journal, Vol 38, pp. 589-91.
• Langer, Arthur M., Roger G. Morse (2001) "The World Trade Center Catastrophe: Was the Type of Spray Fire Proofing a Factor in the Collapse of the Twin Towers?", Indoor and Built Environment. 10(6):350-360.
• Mahmoodi, P., Robertson, L.E., et al (2002) "Performance of Viscoelastic Dampers in World Trade Center Towers", Dynamics of Structures, p. 632-644.
• Monahan, Bernard (2002) "World Trade Center Collapse - Civil Engineering Considerations", Practice Periodical on Structural Design and Construction, ASCE, Vol. 7(3), August 1, 2002.
• Newland, D.E., D. Cebon (2002) "Could the World Trade Center have been Modified to Prevent its Collapse?", Journal of Engineering Mechanics, SCE, Vol. 128(7), July 1, 2002, pp. 795-800.
• Omika, Y., E. Fukuzawa et al (2005) "Structural Responses of World Trade Center under Aircraft Attacks", Journal of Structural Engineering, ASCE, Vol 131(1), January 1, 2005.
• Quan, X., N. K. Birnbaum (2002) "Computer simulation of impact and collapse of New York World Trade Center North Tower on September 11" 20th International Symposium on Ballistics, Orlando, 22-27 September 2002
• Quintiere, J.G., M. di Marzo, R. Becker (2002) "A suggested cause of the fire-induced collapse of the World Trade Towers", Fire Safety Journal. 37(7):707-716.
• Wierzbicki, T., X. Teng (2002) "How the airplane wing cut through the exterior columns of the World Trade Center", International Journal of Impact Engineering.
• 9/11 demolition theory challenged

Other debunking sites:

• Debunking 911 (First time in history?, Free fall?, Molten metal, more debunking)
• 911myths (Demolition?, Other WTC myths)
• AE911Truth.INFO