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Why Fact-check? Why preserve a visual record?

The Website Written as a Book
1: Science and Subjective Viewpoints
2: Toward Accurate Collapse Histories
....2.1: Progressive Floor Collapses in the WTC Towers
....2.2: General Global Characteristics of Collapses
....2.3: Mathematical Basis of ROOSD Propagation
....2.4: WTC1 Accurate Collapse History
....2.5: WTC2 Accurate Collapse History
....2.6: WTC7 Accurate Collapse History
3: WTC Collapse Misrepresentations
....3.1: Purpose of the NIST Reports
....3.2: NIST WTC1 Misrepresentations
....3.3: NIST WTC7 Misrepresentations
....3.4: NIST WTC2 Misrepresentations
....3.5: Reviewing the Purpose of NIST and FEMA Reports
....3.6: Bazant Misrepresentation of Collapse Progressions
....3.7: Block Misrepresentations of Collapse Progressions
....3.8: AE911T Misrepresentations of the Collapses
4: Scientific Institutions Can Be Unaware of Contradiction
5: Reassessing the Question of Demolition
....5.1: The Case of WTC1
....5.2: The Case of WTC2
....5.3: The Case of WTC7
6: WTC Collapse Records Studied as Meme Replication
....6.1: Meme Replication in Technical Literature
....6.2: Meme Replication in Mass Media
....6.3: Meme Replication in Popular Culture
....6.4: John Q Public and the WTC Collapse Records

WTC Twin Towers Collapse Dynamics

Official, Legal Attempts to Explain Collapses

Academic Attempts to Explain Collapses Reviewed

On the Limits of Science and Technology

WTC Video Record

WTC Photographic Record
WTC1 Attack to Collapse
WTC2 Attack to Collapse
Fire Progression, WTC1 North Face
Fire Progression, WTC1 South Face
Fire Progression, WTC1 East Face
Fire Progression, WTC1 West Face
Fire Progression, WTC2 North Face
Fire Progression, WTC2 South Face
Fire Progression, WTC2 East Face
Fire Progression, WTC2 West Face
Debris: WTC1 Around Footprint
Debris: WTC2 Around Footprint
Debris: From WTC1 Westward
Debris: From WTC1 Northward
Debris: From WTC2 Eastward
Debris: From WTC2 Southward
Debris: Plaza Area, Northeast Complex
Debris: Hilton Hotel, Southwest Complex
Debris: General, Unidentified Locations
Damage to Surrounding Buildings
Perimeter Column Photo Record
Perimeter Columns: Types of Damage
Core Box Columns: Types of Damage
Complete Photo Archive
Other Major 9-11 Photo Archives
The 911Dataset Project

WTC Structural Information

Log In


Remember Me

Online Misrepresentations of the WTC Collapses

Forum, Blog Representations of the WTC Collapses

The Book Tested Through Experiments

Miscellaneous Notes, Resources
FAQ for Miscellaneous Notes
History Commons 9/11 Timeline
The 911Dataset Project
Skyscraper Safety Campaign
First and Largest 9/11 Conspiracy Theory
Key Words in Book and Website
Trapped Within a Narrowed False Choice
Vulnerability and Requestioning
On Memes and Memetics
Obedience, Conformity and Mental Structure
Denial, Avoidance (Taboo) and Mental Structure
Taboos Against Reviewing the Collapse Events
Extreme Situations and Mental Structure
Suggestibility, Hypnosis and Mental Structure
Awareness and Behavior
Magical, Religious, Scientific Cause-Effect Relations
The Extreme Limits of Mental Dysfunction
Orwell's "Crimestop", "Doublethink", "Blackwhite"
William James, Max Born: Science as Philosophy
Plato on Self Reflection and Mental Structure
Rewriting History, part 1
Rewriting History, part 2
On Smart Idiots

New Ideas in Education

Usmani. Chung, Torero: Initiation Model

Usmani. Chung, Torero: Initiation Model

by A.S. Usmani, Y.C.Chung and J.L.Torero

The paper is available at this link.

An excellent critique of the paper here:

Usmani-Chung-Torero hypothetical WTC twin towers collapse initiation mechanism.

This is the initial condition. Load is applied to the upper portion of the truss.

The initial deflection due to load was about 7 inches (I applied a very heavy load). Next, a heat flux is applied to the lower truss chord to simulate a fire below.

Over time, the truss sags. After heating to about 1,300°F, the truss sags to 25 inches and pulls in the perimeter wall by 1.2 inches.

Close-up of the wall at maximum deflection.

I have now started working on using this model in a manner of testing the hypothesis of dropping a truss(s) attached to the perimeter wall onto another truss that is attached to a perimeter wall, to see if it will cause a progressive collapse.

The other FEA I alluded to on the debate both sides forum was one done by Newtons Bits (found here and here).

I created a column with dimensions 14” x 14” x .25” and 37 feet long. E=9,700,000 psi and an applied load at the top and 6 kips in the middle.

The maximum deflection was 1.58 inches.

The minimum load to initiate instability for a E=9,700,000 psi column was around 40 kips, applied in middle.

Progression of the instability (I fused together several steps into one picture)2

Here are the results of adding a horizontal force to the existing model.

First, I added a 6 kips horizontal “push-in” force. The maximum inward bowing of the column increased from 1.2” (w/o horizontal force) to 1.75”

I then decided to see what would happen if I increased the load. I applied 50 kips.

Here was the corresponding chart for inward bowing. Notice initially the bowing increased to a maximum of about 2.5”, then as the truss continued to heat up, the expansion coefficient (as a function of temperature) caused the column to be pushed back a little. However, something happened at around time 52. There was a “jump” of some sort and the perimeter column continued to bow inward as time and heat increased.

Here was the reason for the “jump”. As the truss continued to heat up and push back against the perimeter column, the truss eventually deformed out of the x-y plane.

This could very well explain what was happening in the Usmani model. Prior to around 1,850 seconds, the column and truss behaved as predicted. However, at around 1,850 seconds, several data points were taken in close proximity.

From 1,850 seconds onward, the rate of perimeter inward bowing increased faster than the truss sag. There is the possibility that Usmani used a horizontal force to induce inward bowing of the perimeter column.3

I put together the Usmani model to see if there was any truth to his conclusions. In short, the answer is no.

Here is my model (all 12 floors):

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The three red trusses in the middle are the ones heated up to simulate a two story fire.

I used all 3D shell elements to reduce the analysis time. Usmani used 2D shell elements for the trusses and a beam element for the perimeter wall. On the three heated floors, I used concrete and a 8 kN/m load. On the other floors, I used the equivalent of 8 kN/m. Usmani did not provide the properties for the steel or concrete so I used what was in NIST NCSTAR 1-6D.

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I used the same constraints for the perimeter column and truss ends and the temperature profile as given in Usmani figure 9. The image below is after heating for 3,600 seconds. It isn’t surprising that all we get is expansion and pushing on the perimeter column and sag in the truss.

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It isn’t much different than what I analyzed in an earlier FEA.

In the next image, I had to manipulate the forces in order to get the necessary buckling. First, I applied a horizontal force around 150 kips and an out of plane force of 3 kips to cause buckling in the z direction. The model resisted the buckling as shown below.

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You can see the end of the truss going through the perimeter column on the left. In reality, there would be eight locations where the bridging truss would prevent the z direction buckling.

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Usmani was analyzing in 2D and hence they should not get any out of plane buckling, assuming they modeled everything correctly. Even in my model, I wasn’t getting any out of plane action since forces were in the y direction and everything was perfectly symmetrical. I had to induce the out of plane buckling.

Here is a video showing the animation.4

Here is a better view of the discrepancy in the shell model when I added in the horizontal and out of plane forces. It really isn't disconnected, but as the truss chord deforms, it penetrates into the perimeter column since it doesn’t know the geometry is there. I didn't set the flag to check the model for self interaction or parts coming into contact with other parts. If I did, you would not see this penetration and the chord would bend around the perimeter column. It would take more computer time and wouldn’t change the overall result.

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My point was that in order to obtain the results of Usmani, one would need to apply a non-existent horizontal force and ensure the truss deforms out of the z-plane. This is something that should not happen in a 2D analysis.

Instead of fixing and redo the shell model, I went ahead and created the three fire floors using solid elements. They are what Usmani claims to have modeled in his 2D shell and beam analysis. This is about as accurate as one can get without actually building a full scale model.

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It was a waste of time adding in the other 9 floors and they only added to the lateral stiffness of the perimeter wall. So I left them out.

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I applied the 8kN/m load to the floor and raised the temperature of the truss from 20 C to 600 C using the 2 floor profile given in Usmani over 3,600 seconds. Note, the displacements as compared to the shell model (17” vs. 25” vertical).

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Heating the floor truss basically pushed the perimeter wall out. Therefore, I had to again add in horizontal and out of plane forces.

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Even though it isn’t easy to see, the perimeter wall was initially pushed out but the horizontal and out of plane forces pushed it back in.

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Here is a better perspective.

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Here is a chart of the previous model. Note the lateral displacement of the wall initially dips below the x-axis (pushed out), then goes positive (pushed in). I applied quite a bit of load just to get about 5 inches. The NIST considers this pull-in force the reason for the column being pulled in.

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The reason I could not get higher than 5 inches pull in deflection is when I continue to add horizontal force, the perimeter column collapses into itself. This is something that cannot be observed in Usmani’s 2D shell and beam model.

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Here is a video showing the animation.5

Follow up discussion here


1 Critique originally posted by Enik at this link

2 from this post

3 from this post

4 from this post

5 from this post

Created on 10/10/2010 08:26 PM by admin
Updated on 09/25/2012 09:43 PM by admin
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