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News ::
EVIDENCE OF EXPLOSIVES IN THE SOUTH TOWER COLLAPSE. (english)
02 Dec 2002
Modified: 03 Dec 2002
This Article Claims Evidence of Explosives In The South Tower Collapse. What do you think? (article 1)
rows-of-explosives-small.jpg
This Article Claims Evidence of Explosives In The South Tower Collapse. What do you think? (article 1)
rows-of-explosives-small.jpg
This Article Claims Evidence of Explosives In The South Tower Collapse. What do you think? (article 2)

Evidence of Explosives In The South Tower Collapse.
The evidence showing that the World Trade Center towers were demolished is compelling. Here are a few photos of explosives detonating during the collapse of the South Tower. Each frame is numbered by its position in the video. The video was shot at 30 frames per second. So an eight frame interval covers about one quarter of a second.




Frame 147 shows a row of explosives detonating right across the east face at the 79th floor.
Frame 203 shows a row of explosives detonating right across the east face at the 75th floor.

The middle photos show the dust from the explosions outlined in red.

The end photos show the relative positions of the two lines of dust.

It has been claimed that the explosions of dust that span the east face of the tower, were caused by air being forced from the windows as each of the floors above collapsed. This explanation is obviously incorrect. If it was correct, such lines of dust would have been expelled from the windows of each floor in succession. That is, we would have seen such lines of dust expelled from floors 79, 78, 77, 76 and 75 in succession, but what we observe is an explosion of dust at floor 79, no new clouds of dust for a few floors, then another explosion of dust at floor 75. It is worth noting that the second line of (much larger) explosions occur at the center of a section of mechanical floors (the three mechanical floors appear as a slightly darker gray band across the building and are important for the strength they impart to the building). It is possible that the mechanical floors 76 and 75 (and also 74) have no windows, but of course, if this is so, it raises many more questions than it answers. In particular, if the mechanical floors have no windows, then the explosions of dust from floor 75 cannot be caused by air being forced from them as the floors above collapsed.

The dust due to the visible explosions is a whitish grey. The dust from the demolition of the upper section (which is disintegrating as it falls) is dark grey. One wonders what caused this difference.

A sequence of still photos of the collapse (at quarter second intervals) is included at the bottom of this page.




In frames below, we can see that the top 35 or so floors have snapped off and are toppling eastward. In the above frames we follow the north-east corner of the tower as this 35 floor section collapses. Using the north-east corner as a reference I have outlined in red the progress of this 35 floor top section as it descends.

The first thing to note is that the top section itself must be disintegrating otherwise (as the above frames show) the top section would have extended far into parts of the building that are clearly as yet unaffected by the collapse.

But what could possibly cause the top section to disintegrate? And in fact, what could possibly cause the top section to almost entirely disintegrate, before the lower section begins to collapse?

You have to realize that most of the top section had not been affected by the aircraft strike or fires and was thus still the same immensely strong structure that had supported the building for more than 30 years. If this section was going to fall at all, this section would fall as one piece (like a tree in the forest). Unless, of course, this section had been laced with explosives and was undergoing a controlled demolition of its own, just a few moments before the lower part of the building was demolished.

For the full article see: Evidence of Explosives In The South Tower Collapse.
For a full list of articles from http://www.nerdcities.com/guardian, click here.
See also:
http://www.nerdcities.com/guardian
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Why bother with Science? (english)
03 Dec 2002
FORENSIC ENGINEERING
Study Absolves Twin Tower Trusses, Fireproofing

(11/04/2002)
By Nadine M. Post
Engineering News-Record

The most comprehensive study yet on the destruction of the World Trade Center concludes that columns robbed of fireproofing failed first--not floor trusses--when the twin 110-story towers collapsed after being hit by terrorist plane attacks on Sept. 11, 2001. The proof is in the smoke that emanated from the burning towers before the collapses.

"There is no doubt left about the sequence of failure," says Matthys P. Levy, chairman of Weidlinger Associates Inc., the New York City-based engineer that led the study.

"Failure of the floors...was shown not to have had any significant role in the initiation of the collapses," says the report. Levy describes the floor truss system as "not unsubstantial," acting more like a membrane than a one-way system. "There was nothing wrong with it," he says. If the floor trusses had collapsed first, there would have been a mass of smoke as opposed to differentiated smoke, floor by floor, he adds.

photo: ONE WTC http://enr.construction.com/images/021104-13Ba.gif
photo: TWO WTC http://enr.construction.com/images/021104-13Bb.gif
caption: IMPACT SEQUENCE OF HITS--Planes caused different damage (Graphics courtesy of Weidlinger Associates Inc.)

The report also exonerates the steel's sprayed-on fireproofing. Computer models that identify the columns affected by the planes' impacts and flying debris confirm that columns with intact fireproofing did not succumb to the jet- fuel-triggered fire. The report also says, of the fireproofing knocked off the steel, that "no fireproofing is designed to withstand such devastating impacts."

Levy echoes preliminary reports. "The buildings were well-designed, rugged and withstood a tremendous impact," he says. "The fact that they did not collapse on the planes' impacts saved tens of thousands of lives."

photo: http://enr.construction.com/images/021104-12A.jpg
caption: SMOKE PROOF--Engineers say smoke patterns are evidence that columns failed first, not floors. (Photo by Tom Sawyer for ENR)

Questions brought into the limelight by Sept. 11 include whether there is a better way to fight fires in tall buildings, says the engineer. "It's always been a problem," says Levy.

Another issue is whether less-frangible fireproofing should be considered for steel structures considered vulnerable to blasts and attacks. Experts might also reconsider location of fire stairs and the strengthening of the core, says Levy. But he cautions, "You can never anticipate exactly what the threat is going to be."

Regarding building materials, Levy says: "Concrete is not foolproof either."

The Weidlinger-led study was commissioned by Silverstein Properties Inc., the New York City-based leaseholder of the World Trade Center, to help support a $7-billion insurance claim. The research team also included LZA Technology/Thornton-Tomasetti Group; ARUPFire; Hughes Associates Inc.; SafirRosetti; Hillman Environmental Group; RWDI; W. Gene Corley, who led the ASCE-FEMA WTC study; Professor Sean Ahearn; and Z-Axis Corp.

Silverstein's insurers claim the collapse of the south tower, Two WTC, rendered the north tower, One WTC, unsalvageable even before it collapsed. If they prevail, Silverstein would receive only $3.5 billion (ENR 10/7 p. 11).

photo: http://enr.construction.com/images/021104-12C.jpg
caption: SECOND DOWN--North tower lasted longer due to impact site. (Graphics courtesy of Weidlinger Associates Inc.)

The insurers commissioned their own engineering study, written by Exponent Failure Analysis Associates Inc., Los Angeles. Also released, the report disagrees with the Weidlinger findings, but mostly on points relating to the insurance battle. Engineers from Wiss, Janney, Elstner and Associates Inc., Northbrook, Ill., also working for the insurers, would not comment on their work.

In the Silverstein study, engineers put forth similar but not exact failure scenarios for both towers: The planes and flying debris hobbled the buildings at the zones of impact. Intact columns, their fireproofing knocked off by flying debris, ultimately lost strength and failed in the fuel-triggered fire.

Though hit by the second plane later than One WTC, Two WTC fell first, "primarily" because the plane struck it off-center and at an angle and caused damage that compromised the southeast corner of the core. "This confirms an earlier theory," says Levy

photo: http://enr.construction.com/images/021104-12B.jpg
caption: FIRST DOWN--Plane took out corner of core, which hastened collapse.(Graphics courtesy of Weidlinger Associates Inc.)

At each tower, exterior wall and core columns, connected by a steel "hat truss" at the building's top, initially redistributed loads away from the damaged areas to remaining columns. In Two WTC, the hat truss eventually could not deal with the situation of the corner columns gone, says Levy.

The team determined that the initial hits destroyed 33 of 59 perimeter columns in the north face of One WTC and 29 of 59 perimeter columns in the south face of Two WTC. Computer analysis showed that the impact of the planes also destroyed or disabled some 20 of 47 columns in the center of the core of One WTC and some five of 47 columns in the southeast corner of the core of Two WTC.

The Silverstein findings are based on analysis of original structural drawings, thousands of photos and dozens of videos. The team used computer modeling, including a program called FLEX developed by Weidlinger for the Dept. of Defense, and fire evaluation techniques to simulate the condition of each tower at critical times, creating impact and collapse sequences.

The National Institute of Standards and Technology, which recently began a two-year technical study on the World Trade Center disaster, is using both team's studies to perform a "very systematic" analysis, says S. Shyam Sunder, chief of NIST's materials and construction research division, Gaithersburg, Md. "The real question is whether there was one dominant failure mechanism or a combination," he adds.
See also:
http://enr.construction.com/news/buildings/archives/021104.asp
What is the purpose of Science? (english)
03 Dec 2002
FORENSIC ENGINEERING
Study Absolves Twin Tower Trusses, Fireproofing

(11/04/2002)
By Nadine M. Post
Engineering News-Record

The most comprehensive study yet on the destruction of the World Trade Center concludes that columns robbed of fireproofing failed first--not floor trusses--when the twin 110-story towers collapsed after being hit by terrorist plane attacks on Sept. 11, 2001. The proof is in the smoke that emanated from the burning towers before the collapses.

"There is no doubt left about the sequence of failure," says Matthys P. Levy, chairman of Weidlinger Associates Inc., the New York City-based engineer that led the study.

"Failure of the floors...was shown not to have had any significant role in the initiation of the collapses," says the report. Levy describes the floor truss system as "not unsubstantial," acting more like a membrane than a one-way system. "There was nothing wrong with it," he says. If the floor trusses had collapsed first, there would have been a mass of smoke as opposed to differentiated smoke, floor by floor, he adds.

photo: ONE WTC http://enr.construction.com/images/021104-13Ba.gif
photo: TWO WTC http://enr.construction.com/images/021104-13Bb.gif
caption: IMPACT SEQUENCE OF HITS--Planes caused different damage (Graphics courtesy of Weidlinger Associates Inc.)

The report also exonerates the steel's sprayed-on fireproofing. Computer models that identify the columns affected by the planes' impacts and flying debris confirm that columns with intact fireproofing did not succumb to the jet- fuel-triggered fire. The report also says, of the fireproofing knocked off the steel, that "no fireproofing is designed to withstand such devastating impacts."

Levy echoes preliminary reports. "The buildings were well-designed, rugged and withstood a tremendous impact," he says. "The fact that they did not collapse on the planes' impacts saved tens of thousands of lives."

photo: http://enr.construction.com/images/021104-12A.jpg
caption: SMOKE PROOF--Engineers say smoke patterns are evidence that columns failed first, not floors. (Photo by Tom Sawyer for ENR)

Questions brought into the limelight by Sept. 11 include whether there is a better way to fight fires in tall buildings, says the engineer. "It's always been a problem," says Levy.

Another issue is whether less-frangible fireproofing should be considered for steel structures considered vulnerable to blasts and attacks. Experts might also reconsider location of fire stairs and the strengthening of the core, says Levy. But he cautions, "You can never anticipate exactly what the threat is going to be."

Regarding building materials, Levy says: "Concrete is not foolproof either."

The Weidlinger-led study was commissioned by Silverstein Properties Inc., the New York City-based leaseholder of the World Trade Center, to help support a $7-billion insurance claim. The research team also included LZA Technology/Thornton-Tomasetti Group; ARUPFire; Hughes Associates Inc.; SafirRosetti; Hillman Environmental Group; RWDI; W. Gene Corley, who led the ASCE-FEMA WTC study; Professor Sean Ahearn; and Z-Axis Corp.

Silverstein's insurers claim the collapse of the south tower, Two WTC, rendered the north tower, One WTC, unsalvageable even before it collapsed. If they prevail, Silverstein would receive only $3.5 billion (ENR 10/7 p. 11).

photo: http://enr.construction.com/images/021104-12C.jpg
caption: SECOND DOWN--North tower lasted longer due to impact site. (Graphics courtesy of Weidlinger Associates Inc.)

The insurers commissioned their own engineering study, written by Exponent Failure Analysis Associates Inc., Los Angeles. Also released, the report disagrees with the Weidlinger findings, but mostly on points relating to the insurance battle. Engineers from Wiss, Janney, Elstner and Associates Inc., Northbrook, Ill., also working for the insurers, would not comment on their work.

In the Silverstein study, engineers put forth similar but not exact failure scenarios for both towers: The planes and flying debris hobbled the buildings at the zones of impact. Intact columns, their fireproofing knocked off by flying debris, ultimately lost strength and failed in the fuel-triggered fire.

Though hit by the second plane later than One WTC, Two WTC fell first, "primarily" because the plane struck it off-center and at an angle and caused damage that compromised the southeast corner of the core. "This confirms an earlier theory," says Levy

photo: http://enr.construction.com/images/021104-12B.jpg
caption: FIRST DOWN--Plane took out corner of core, which hastened collapse.(Graphics courtesy of Weidlinger Associates Inc.)

At each tower, exterior wall and core columns, connected by a steel "hat truss" at the building's top, initially redistributed loads away from the damaged areas to remaining columns. In Two WTC, the hat truss eventually could not deal with the situation of the corner columns gone, says Levy.

The team determined that the initial hits destroyed 33 of 59 perimeter columns in the north face of One WTC and 29 of 59 perimeter columns in the south face of Two WTC. Computer analysis showed that the impact of the planes also destroyed or disabled some 20 of 47 columns in the center of the core of One WTC and some five of 47 columns in the southeast corner of the core of Two WTC.

The Silverstein findings are based on analysis of original structural drawings, thousands of photos and dozens of videos. The team used computer modeling, including a program called FLEX developed by Weidlinger for the Dept. of Defense, and fire evaluation techniques to simulate the condition of each tower at critical times, creating impact and collapse sequences.

The National Institute of Standards and Technology, which recently began a two-year technical study on the World Trade Center disaster, is using both team's studies to perform a "very systematic" analysis, says S. Shyam Sunder, chief of NIST's materials and construction research division, Gaithersburg, Md. "The real question is whether there was one dominant failure mechanism or a combination," he adds.
See also:
http://enr.construction.com/news/buildings/archives/021104.asp