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Originally posted by Seventh
the way we like to deal with WTC7 is the good old fashioned US of A way..... don`t even mention it, works wonders.
www.structuremag.org...
Single Point of Failure
How the Loss of One Column May Have Led to the Collapse of WTC 7
Ramon Gilsanz, P.E., S.E., Willa Ng
The collapses of World Trade Center 1 (WTC 1) and World Trade Center 2 (WTC 2) on September 11, 2001 were attributed to the impact of two airplanes and the ensuing fires. The subsequent collapse of World Trade Center 7 (WTC 7), which was not directly struck by airplanes, is more of an enigma. Additionally, the nature of its collapse, which occurred nearly seven hours after WTC 1 and WTC 2 failed, has led to rampant speculation.
The following analysis shows that, although there were several phases leading to the global collapse of WTC 7, the building likely would have remained standing if not for the failure of one critical column. The location of this column, and its role as a key structural component, meant that its local failure caused the global failure of WTC 7.
The Federal Emergency Management Agency (FEMA) Building Performance Assessment Team and the National Institute of Standards and Technology (NIST) formed a team to analyze the collapse of WTC 7. The effort began with the collection of structural pieces, existing plans, eyewitness accounts, and photos and videos taken that day. This information led to the formation of several probable collapse theories. The team then created a computerized model of the building, using existing plans and information, to test these theories.
WTC 7, one of the seven buildings that formed the World Trade Center complex in New York City, was bounded by Washington Street, West Broadway, Barclay Street and Vesey Street. This 47-story commercial office building was approximately 330 feet long, 140 feet wide and 610 feet tall, and was constructed over a pre-existing electrical substation owned by Con Edison. The original plans for the substation included the construction of a high-rise tower above it.
However, the final footprint of WTC 7 was larger than the originally planned high-rise tower. As a result, there were discontinuities between the columns in the Con Edison substation and the columns for the rest of WTC 7. Braced frames, transfer trusses and transfer girders at floors 5 through 7 transferred loads between the discontinuous columns. These elements, though serving the purpose of shifting loads from one set of columns to another, also essentially "tied" the columns to each other. The columns were numbered for ease of identification and will be referred to by their number herein.
The failure of WTC 1 and WTC 2 sent flaming debris into the southern face of WTC 7. This impact and fire damage initiated a sequence that would lead to global collapse. Eyewitness observations by building occupants, NYPD, FDNY and bystanders indicated that the damage was located on the south face between floors 8 and 18, and that there was a fully involved fire on the south side of floor 7, which included the transfer elements. From 3:00 to 5:00 PM, fires were still burning in the building, which may explain why it took several hours for it to collapse. The continued heat of the fire weakened steel structural components until they failed at 5:21 PM, nearly seven hours after the collapse of WTC 1 and WTC 2.
The final collapse of WTC 7 occurred over 8.2 seconds and was recorded on several videos from locations northeast and northwest of the building. Study of these videos led to the development of the timeline of the visible external sequence of events. The images accompanying this article are taken from a CBS News Archives video to show key points observed during the collapse. As seen in the photos, a kink develops in the east penthouse before it falls into the building. The west penthouse then fails, followed by a kink in the entire façade of the building. Total collapse follows.
This sequence of events, with roof elements sinking into a building with an intact façade, suggests an interior failure. An interior failure would explain the appearance of a "controlled" collapse with a relatively small debris field, as seen with WTC 7.
The sequence of final collapse can be interpreted using knowledge of the building’s framing from existing plans. For instance, the observed collapse of the east penthouse may signify a failure in a line of columns on the east side of the building (columns 76-81). In particular, interior columns 79, 80 and 81 were located directly below the east penthouse and supported relatively large tributary areas.
The final collapse hypothesis can be summarized as follows:
1) Debris from the collapse of WTC 1 and WTC 2 caused damage from impact and fire.
2) Fire significantly weakened structural steel and caused the failure of one or more of the columns on the eastern side of the building, as evidenced in the sinking of the east penthouse. This indicated a vertical progression of failure from the damage on the lower floors to the failure of the penthouse on the roof.
3) The sinking of the west penthouse, as well as the shifting of a clear kink from the east penthouse towards the middle of the structure, indicates that the collapse then progressed horizontally, as the localized failure of the eastern columns was distributed to the other columns through the transfer elements at floors 5 through 7.
4) Global collapse was the ultimate result.
A kinematic model was created to test the final collapse hypothesis and isolate the structural elements that may have contributed to each phase of the failure. It was this testing that isolated one column, 79, as the critical structural component whose failure led to global collapse. A collapse mechanism analysis performed for the removal of column 79 produced a deformed shape with a kink in the roof of the east penthouse, as captured in actual videos and photos taken that day.
The video, photographic and first-person account evidence of the collapse of WTC 7 suggests that the impact of debris and resulting fire contributed to the collapse through the weakening of key structural components. The sequence of collapse, most notably the observed behavior of the penthouses, points to several key columns as the first to fail. The failure of column 79 was pivotal in the subsequent global collapse. As shown in the computerized non-linear structural model, its failure initiated the vertical collapse progression. WTC 7’s properties of load transfer at floors 5 and 7, when combined with the failure of column 79, led to a horizontal collapse progression, which in turn ultimately resulted in global collapse.
The results of the research performed on WTC 7 suggest that steps can be taken to avoid vulnerabilities in the design of buildings, though no design can be expected to withstand the events of September 11, 2001. The original designers and builders of WTC 7 could not have had any idea that this structure would have to resist such forces.
However, the vulnerability of WTC 7 was that damage, though significant, should have caused no more than local failure of structural components. That is, buildings should be designed to survive a local failure, due to blast, fire, impact, etc. but prevent the progression of a collapse throughout the structure.
STRUCTURE magazine November 2007
www.structuremag.org...
11-settembre.blogspot.com...
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Originally posted by mmiichael
It should be evident to anyone who thinks about it Silverstein (note spelling) tells the firemen to "Pull it" because he's concerned they'll stay trying to fight the fire in a building that's on the verge of collapsing as attested to by hundreds of photographs and witnesses. It was already leaning and creaking 2 hours before.
Originally posted by titorite
This is not a cryptic innuendo or some obscure quasi reference that must be inferred. This dude said that the smartest thing to do would be to pull it, so they pulled it. Then it fell. How much more clear does the man need to be?!?!
That rectangular building was not leaning. IF it leaned in any direction other debunkers better ones than yourself would of posted pics of it long ago. That comment is dis-information. WTC 7 never leaned. It just fell flat in onto itself.
Originally posted by visible_villain
reply to post by Neo-V™
Your OP said :
Botched Building Demolition Reinforces WTC 7 Lie...
I just thought I would point out that this building is a reinforced concrete structure, not a structural steel frame building, so the analogy you are making doesn't not hold.
Don't get me wrong : I am not trying to debunk the controlled demolition theory of the WTC, just only that your OP is comparing apples and oranges.
Pretty good clip though.
Originally posted by mmiichael
Originally posted by Seventh
the way we like to deal with WTC7 is the good old fashioned US of A way..... don`t even mention it, works wonders.
I've read maybe half a dozen porofessional analyses of what caused WTC 7 to collapse, not all American. They pretty much concur. No one, except in Conspiracy Land, has ever found compelling scientific evidence of a controlled demolition, which is tough to argue as the building was seen gradually losing it's ability to support itself in the final two hours.
You missed my whole point of that post bud, think commission, think WTC7, it wasn`t even mentioned, that`s what I meant.
Originally posted by Nunny
reply to post by Neo-V™
Uh-huh. And did they start fires that heated to 2000 degrees for 1 hour so that it WEAKENED the steel so that it had 1/2 the strength as usual? And did they look to see if the building followed the same architectual patterns as the WTC so that they were comparing apples to apples? Didn't think so. You people SERIOUSLY need to move on to things that are obviously wrong and proveable. Otherwise, you will simply be written off as "we didn't go to the moon" people.
Check out MIT, Princeton, and virtually EVERY news agency in the world. They all CONFIRM the Physics that were in play and the cause. The fire didn't MELT the steel. It weakened the steel. So the steel that was supposed to be able to hold X tons could only support ½X tons. When one failed, it put more stress on the other beams and that's the end of the story.
Originally posted by thedman
reply to post by Seventh
You missed my whole point of that post bud, think commission, think WTC7, it wasn`t even mentioned, that`s what I meant.
No you have the point - the commission was to investigate how the
hijackers got control of the aircraft and were able to fly them into
buildings.
As pointed out by you loons WTC 7 was not struck by a plane - it was
COLLATERAL DAMAGE (as was WTC 3 (Marriott Hotel), WTC 4, 5, 6,
130 Liberty St (Deutsche Bank), St Nicolas Orthodox Church and 30
West Broadway - which was collateral damage from WTC 7 collapse)
I dont see you whining about any of these other buildings which were
destroyed that day too
In WTC 3 (Marriott) 40 firefighters who were searching building and using
as staging area were killed along with several Marriott employees and
civilians
Why are not demanding investigation into why WTC 3 collapsed? Over
50 people died in it compared to WTC 7 where NOBODY was killed....
Originally posted by Donny 4 million
reply to post by mmiichael
Mike, do you have any other sources for the reason bldg. 7 was demolished or just the structual magezine one?
Anyway your are going to need more because that magizine article if you read it all, says it is a scenario created by a hypothesis applied to a model to determine want coloum would fail first based on the penthouese's collapsing one after the other. They provide no direct reason for the failure of that particular piece of steel and what is more telling is that they do not rule out demolishion as the cause of the collapse and never mention thermite.
Demolition is not explored because there has never been any indication of it. No synchronized explosions, forensic residues, caps, cabling, etc.
Originally posted by Nutter
reply to post by thedman
Did these bomb squad guys have extensive knowledge of all the military's arsenal? (I highly doubt it as thermobarics and nano-thermate weren't even known to the public sector back then.)
Or where they looking for "conventional" explosives only?
11-settembre.blogspot.com...