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9/11
See other 9/11 Articles

Title: Purdue University sticks it to the 9-11 "Truthers"
Source: churchoftheduke.blogspot.
URL Source: http://churchoftheduke.blogspot.com ... versity-sticks-it-to-9-11.html
Published: Jun 21, 2007
Author: churchoftheduke.blogspot.
Post Date: 2007-06-21 13:28:28 by can of corn
Keywords: twoofers, tinfoil hat, moonbats
Views: 205
Comments: 11

Makes me damn proud of my associated with Purdue, actually. The short version is that researchers at Purdue, which is known for having one of the finest engineering schools in the country, have concluded a 2.5 year study on the 9/11 attacks. The focus of the study was to examine the structural failure of the WTC towers with an eye towards designing buildings that could withstand aircraft strikes. The full article on http://CNN.com is here.

The researchers also posted a simple computer model of the attack on Youtube, which I've linked to here. I will say, that if you don't like reading the absolutely inane drivel of the 9/11 "Truthers", then don't read the comments on the video.

This excerpt is from the CNN article.

A computer simulation of the September 11, 2001, attack on the World Trade Center, posted on the Web site YouTube by Purdue University researchers, shows how hijacked planes crashed through the twin towers, stripping fireproofing materials from the steel columns and eventually leading to their collapse.

Of course, this won't actually do anything to shut up the "Inside Job" movement, who amongst conspiracy theorists have the remarkable ability to jam their fingers in their ears and not listen to reason.

Unfortunately, as proud as I am of Purdue for releasing this study; I also know it won't do any good with the conspiracy types. Not because I think the study is flawed or anything silly like that, mind you. It's because you can't argue with a conspiracy theorist. Since they're not dealing with reality, any factual evidence can explained away by another government coverup. It must be great to be able to just make stuff up when the evidence stands against you.

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#9. To: can of corn (#0)

http://www.cs.purdue.edu/homes/cmh/simulation/phase3/WTC-1_EP.pdf [PDF]

http://tinyurl.com/29nld6 [HTML]

An Engineering Perspective of the Collapse of WTC-I

Ayhan Irfanoglu and Christoph M. Hoffmann

Abstract:

We report on a simulation study of the performance of the North Tower (WTC-I) of the World Trade Center complex during the impact of American Airline Flight 77, on September 11, 2001. We discuss impact damage the structural core might have sustained and its possible behavior under structural and thermal loading. Our simulations indicate that the worst damage to the core structure was in stories 95 through 97 of the tower. We estimate that a core collapse mechanism could be initiated if the tower core column temperatures were elevated to about 700ºC.

...

No detailed observational data on the performance of tower core elements exist. Therefore, the Purdue research team used finite element simulations to assist in estimating the impact response and the post-impact state of the structural elements in the core. Objective evaluations of the simulation results indicated that identification of the number and distribution of columns damaged immediately by the impact was quite sensitive to the input parameters. As would be expected, the simulations did indicate consistently some damage to the core columns but credible changes in input parameters such as flight or column properties resulted in changes in calculated impact damage suggesting that an exact determination of the damage to the core was not defensible. On the other hand, it was found that a simple construct, not dependent on exact identification of the damage distribution, would explain the collapse.

The study concentrated on the core structure of the tower and its possible behavior under impact and thermal loads. It was not the purpose of the study to rule out other plausible mechanisms initiating collapse of the WTC-I tower, such as one due to loss of lateral bracing and buckling of perimeter columns induced by failure of open-web floor joists under thermal loads, or other failure mechanisms. Rather, the object of the paper is to show that a simple and credible hypothesis will suffice to explain the observed collapse.

...

Damage to WTC-I core structural elements

There were forty-seven columns arranged in six column lines in the core structure of WTC-I. Figure 6 shows the core columns as well as the perimeter columns on a typical floor plan. Figure 7 shows a perspective view of the columns and floor slab of the 95th story.

Because there is no observational information on the state of core structure after the aircraft impact, computer simulations are used to estimate the damage sustained by the structural elements in WTC-I core.

Table 1 lists the estimated number of heavily damaged core columns according to our final simulation. However, it must be added that during the series of simulations performed, we found the estimates to be very sensitive to model parameters such as failure strain of materials, to the extent that in the heavily damaged stories 95 through 97, the number of damaged columns could be as few as half the numbers listed in Table 1. This observation was not surprising given the fact that simulation results reported by other researchers (see for example, NIST 2005 and Omika et al. 2005) with regards to damage to the core columns are scattered over a wide range. Table 2 lists the estimates for maximum number of destroyed core columns as reported by various research groups.

From the results obtained at Purdue and elsewhere, it is evident that to determine by calculation the exact number of columns damaged by the impact is beyond the technology currently available to us. However, in our simulations, we observed that the heavy damage to the core columns concentrated consistently at stories 95 through 97. This too should not be considered surprising given the fact that the aircraft impacted the WTC-I tower at or very close to floor level 96 and that the airplane had the greatest concentration of mass close to its centerline.

...

The demand and full-core capacity curves in Figure 11 suggest that if 95th story core columns had free heights of 3.6 m, i.e. if they were restrained at the top and bottom of the story, when the core reached approximately 700ºC, the structure would not be able to sustain the axial loads from the stories above and a core collapse would be initiated.

...

When damage to the core columns in story 95 is taken into consideration, the limit state is reached at a lower temperature (see Figure 11). The reduction in the level of critical temperature is estimated to be no more than 50ºC. In other words, even though the aircraft impact loads may have eliminated a significant number of core columns, the damage to core structure had, ultimately, little effect on the critical thermal load level to fail the core under axial gravity loads.

Although not illustrated in here, if the core columns were to lose their lateral supports and their free heights became more than 3.6 meter, even though there would be significant reduction in the total axial load capacity of the core columns, the estimated ultimate failure temperature would not have changed that significantly. For example, doubling the free-height to two-stories reduces the total axial capacity by about 30-40% but reduces the failure temperate to only about 600ºC or about 650ºC if no damage to core columns were considered. Again the damage to core columns from impact loads could be considered immaterial when viewed from ultimate thermal load capacity of the core structure. In thermal load analysis for response of structural elements at high temperatures under actual conditions, the effect of a 50ºC difference in temperature is hardly distinguishable, given all the uncertainties.

It is evident from observation and our simulations that the debris of the aircraft went through the WTC structure at stories 94 through 97. Much of the fire insulation would have been scoured off leaving the steel elements unprotected during the immediately following fire event. Experimental data for steel in that condition (Buchanan 2000) indicate that the metal temperature in all unprotected structural elements would have reached 700ºC in a typical office fire. That condition would suffice to initiate instability (e.g. Ali and O’Connor 2001, Wang and Davies 2003) even if all the girders were intact and the failure mechanism was limited to one story of the core structure.

Conclusions

Impact simulations indicate that the damage states of the WTC-I core structural elements are very sensitive to analysis parameters and as such, it is not possible to suggest the exact state of the core framing after the aircraft impact. Simulations indicate consistently that the worst damage to the core structure was sustained in the 95th through 97th stories of the tower.

For both the intact and plausible compromised core states considered, it is estimated that a core collapse mechanism could have been initiated in WTC-I if the tower core column temperatures were elevated to approximately 700ºC. As the aircraft debris went through several stories in the tower, much of the thermal insulation on the core columns would have been scoured off. Under such conditions, the ensuing fire would be sufficient to cause instability and initiate collapse. From an engineering perspective, impact damage to the core structure had a negligible effect on the critical thermal load required to initiate collapse in the core structure.

Acknowledgments

We thank Prof. Mete A. Sozen for his insight and invaluable support throughout the project. Graduate Research Assistants Paul A. Rosen, Ingo Brachmann, and Oscar A. Ardila-Giraldo developed the numerical models and executed the computer simulations. Konstantinos Miamis provided the base study on thermal behavior of columns.

This project is supported in part by NSF-ITR grant DSC-0325227. Infrastructure support for the large-scale simulations was provided in part by the Northwest Indiana Computational Grid, by the Network for Computational Nanotechnology of Purdue University, and by the Bowen Laboratory for Civil Engineering.

nolu_chan  posted on  2007-06-22   8:15:04 ET  Reply   Untrace   Trace   Private Reply  

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