Monday, November 22, 2010

Steel Matters


Steel Matters



            One of the crucial cruxes in the official government story of why the twin towers collapsed lies within their claim that the steel columns holding up the buildings were significantly weakened by three things: one, the collision of the airplanes two, the loss of the fire resistant coating on the steel, and three the extensive fires that burned after impact.[i] While these conditions enabled the towers to fail the theorized loss of spray-applied fire insulation (SFRM) from the force of the planes’ impact is considered by NIST to be the most important of the three. 
          
            “The towers would not have collapsed under the combined effects of aircraft impact and the
subsequent multifloor fires if the insulation had not been widely dislodged or had been only
minimally dislodged by aircraft impact.[ii]

            While this theory put forth by the National Institutes of Standards and Technology (NIST) portends plausibility, there are a number of questions and inconsistencies in this view that have been raised by other researchers.  We will consider the major ones beginning with a look at the controversy regarding the steel columns in the building.
1.      At what temperature does steel weaken or melt, and what temperatures were observed in the World Trade Centers (WTC) after impact?
a.       Steel melts at approximately 1500º C and, according to NIST, at temperatures of 1000º C steel retains only 10% of its structural integrity. [iii]
b.      NIST reports upper AIR temperatures of 1000º C existed in WTC.[iv]
         Given this set of information from NIST it seems plausible that the WTC could indeed have collapsed given tremendous amount of heat that the structural steel was subjected to.  However, these two points raised by NIST generate far more questions than it attempts to answer by providing this information.  A few of ours are:
How did NIST conclude that the air temperatures inside the WTC were close to 1000º C?
Was the actual steel subject to these intense energy load?
What percentage of the steel was subjected to these temperatures?
What experiments did NIST perform to show the validity of their claims?
            While we certainly have more questions than the above, to exhaustively treat all questions arising from NIST’s work would be beyond the scope of this project. Let us focus on the claims of other experts that seem to counter NIST’s assessments and conclusions of what happened to the steel.
            Let us start with the air temperatures inside the WTC.  Consider the following from Thomas Eager PhD, a professor at MIT:

“In combustion science, there are three basic types of flames, namely, a jet burner, a pre-mixed flame, and a diffuse flame.... In a diffuse flame, the fuel and the oxidant are not mixed before ignition, but flow together in an uncontrolled manner and combust when the fuel/oxidant ratios reach values within the flammable range. A fireplace is a diffuse flame burning in air, as was the WTC fire. Diffuse flames generate the lowest heat intensities of the three flame types... The maximum flame temperature increase for burning hydrocarbons (jet fuel) in air is, thus, about 1000 °C -- hardly sufficient to melt steel at 1500 °C. But it is very difficult to reach this maximum temperature with a diffuse flame. There is nothing to ensure that the fuel and air in a diffuse flame are mixed in the best ratio... This is why the temperatures in a residential fire are usually in the 500 °C to 650 °C range. It is known that the WTC fire was a fuel-rich, diffuse flame as evidenced by the copious black smoke”[v]

We can see that these intense temperatures were possible, but according to Eager these high temperatures were not likely in the WTC. So how did NIST come up with the 1000 degree air temperature result?  And furthermore, did they calculate how long these temperatures were sustained in the WTC?
           
            Since we apparently have no footage from inside the towers or temperature recordings performed after plane impact or prior to collapse on the floors impacted by the airliners, NIST relies on photographs and footage from outside the towers to determine where the fires were, length of burning and to some extent how hot they were.[vi]  They rely primarily on calculating the amount of energy that was available for combustion by burning similar material that was present on the floors of impact in the WTC[vii], and plugging these data into computer models to simulate how hot the fires were.[viii]  Despite NIST’s technical expertise in simulating fires, and calculating the energy given from combustion their findings are still just that, a prediction, and while we consider it plausible that air temperatures could have reached 1000 ºC, that doesn’t mean the steel columns reached that temperature.  Let’s now consider some of the arguments against NIST’s findings.
            First and foremost is that in none of the steel analyzed by NIST reached temperatures above 600 ºC.[ix] Given this striking finding by NIST we must consider this in light of the fact that NIST was only able to analyze 229 samples of steel which they estimate was only 0.25 to 0.5 percent of the total structural steel which comprised the twin towers.[x]  So what happened to the over 200,000 tons of structural steel?
“In the month that lapsed between the terrorist attacks and the deployment of the [FEMA Building Performance Assessment Team (BPAT Team)], a significant amount of steel debris—including most of the steel from the upper floors—was removed from the rubble pile, cut into smaller sections, and either melted at the recycling plant or shipped out of the U.S. Some of the critical pieces of steel—including the suspension trusses from the top of the towers and the internal support columns—were gone before the first BPAT team member ever reached the site”[xi]
            Bill Manning, editor of the Fire Engineering Journal, had this to say about the removal of the steel-the key evidence to why the towers collapsed.
“For more than three months, structural steel from the World Trade Center has been and continues to be cut up and sold for scrap.  Crucial evidence that could answer many questions about high-rise building design practices and performance under fire conditions is on a slow boat to China, never to be seen again in America until you buy your next car.  Such destruction of evidence shows the astounding ignorance of government officials to the value of a thorough, scientific investigation of the largest fire-induced collapse in world history.  I have combed through our national standard for fire investigation, NFPA 921, but nowhere in it does one find an exemption allowing for the destruction of evidence for buildings over 10 stories tall… As things stand now and if they continue in such fashion, the investigation into the World Trade Center fire and collapse will amount to paper- and computer-generated hypotheticals.”[xii]

            So without the structural steel evidence from the collapse of the WTC, how are we to trust NIST’s or anyone’s findings about why the towers collapsed? Instead of relying on empirical evidence, investigations, both official and unofficial, rely on either a non-representative sample, or projections and estimations.

More to come…stay tuned…


[v] Eagar, T. W. and Musso, C. (2001). “Why Did the World Trade Center Collapse? Science, Engineering, and Speculation”, Journal of the Minerals, Metals and Materials Society, 53/12:8-11 (2001).

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