|How NIST Avoided a Real Analysis of the Physical Evidence of WTC Steel|
|Mardi, 23 Août 2011 00:00|
Nous sommes désolés, il n'existe pas de traduction de ce texte pour le moment.|
Editorial Introduction by Dick Zehnle
NIST likes to point out how many scientists and engineers worked on its WTC investigation, and how much time was spent. But the number of participants and the time and money spent does not guarantee a thorough investigation.
In addition, NIST substituted for the common method of unaided visual examination of the steel a novel method of a paint-based visual examination which, by design, eliminates from consideration any steel that was heated to above 650 degrees Celsius, at which temperature the paint would have flaked off. Thus, NIST assured from the outset that it would not even investigate evidence that temperatures above 650 Celsius affected the steel.
An abridged version of the article is provided here and in the newsletter.
NIST's exclusion of most of the steel from being adequately examined
The 236 pieces of structural WTC steel that the National Institute of Standards and Technology (NIST) "catalogued" for its WTC investigation included 55 columns that NIST discusses in paragraph 4.1 "CORE COLUMNS" in NIST NCSTAR 1-3C, of which NIST analyzed only four for damage and failure modes. The remaining 51 columns were excluded from being examined for damage and failure modes based on the argument that only columns with a known as-built location2 in or near the impact and fire areas were of interest for the WTC investigation.3 A similar argument was applied by NIST to the 90 "catalogued" perimeter wall panels4 and their columns. NIST describe "in-depth" only those five of the 90 panels that were located in the airplane impact zone of WTC 1.5 Regarding the remaining 85 panels, NIST states:6 "All damage found on the panels located outside of the impact zone was ascribed to events occurring during and after the collapse, therefore, in-depth descriptions were not reported." The damage and failure modes of about 128 perimeter columns are reported in summary fashion in just a few sentences and in one table with statistical data.7 The following quote by NIST8 underlines that no adequate damage and failure analysis was conducted for those columns: ""While these damage features were observed and recorded for each individual column, no effort was made to quantify the frequency with which the modes occurred for each column …" Likewise, the damage modes of the spandrel connections and end plate connections for panels from outside the impact area and for unidentified panels are summarized in only a few sentences and in tables with statistical data.9
Any serious investigation into the reasons why the Twin Towers were completely destroyed would attempt to find out why the strong steel frames below the impact and fire areas lost their strength and gave way. But NIST deliberately decided not to do this. NIST excluded -- quite systematically and based on the explicit argument that only the few columns with a known as-built location in the impact and fire areas were of interest for the investigation – the columns from the parts that failed and gave way so unexpectedly, i.e., the columns with as-built locations below the impact and fire areas, from being adequately examined for their damage and failure modes. Scientists and engineers in relevant fields should know that those parts of the structure that gave way need to be included in the investigation of a building failure. There are many indications that NIST's scientists and engineers have been actually well aware that the failure of the load bearing structures of the Twin Towers cannot be investigated by focusing exclusively on the collection of data concerning the impact and fire areas. For example, NIST developed a "structural database" that included the data for the structural members from bottom to top. They developed "global structural models" for both Towers that stretched over their full heights. And they analyzed the performances of the undamaged structures for three loading cases, and checked the demand/capacity ratio for the structural components.10 NIST examined (as part of the same "Project 3: Mechanical and Metallurgical Analysis of Structural Steel," which systematically excluded steel from outside the impact and fire areas from being adequately examined) samples of all steel qualities used throughout the buildings to check if they complied with the demanded quality standards.11
NIST cannot justify the exclusion of the steel from being adequately examined for damage and failure modes by its published result of the investigation, i.e., the "how the point of collapse initiation was reached" models and the few lines with suggestions why "global collapse ensued". The named models and suggestions were presented by NIST as results of the investigation, so they should not have influenced decisions at the beginning of the investigation. Examining the evidence and collecting data based on the evidence was a task that NIST needed to perform before any hypotheses were formulated. But NIST excluded columns from outside the impact and fire areas, and columns with an unknown as-built location, from being adequately examined for their damage and failure modes at the very beginning of the investigation. The above quote, "that no effort was made ...," is one of the indications that show that it is not just a reporting problem in the published final report, but a problem of NIST's study design. The named steel was indeed not adequately examined, but excluded from the very beginning.
Thus, by a process of circular reasoning, NIST avoided an adequate analysis of the physical evidence of the steel for data that might have answered the question why the strong steel frames below the impact and fire areas gave way as completely and quickly as they did; by proceeding on the basis of a preconceived premise, NIST compromised the validity of the investigation. In addition, the exclusion from adequate examination of columns with unknown as-built locations, and of columns from above the impact and fire areas cannot be justified. Any column could hold conclusive evidence; one cannot determine that a piece does not yield any useful clues before it has been adequately examined.12
Indeed, NIST excluded the majority of the recovered WTC steel pieces even from being "catalogued" for the investigation. Of the large number of structural steel members collected by the Port Authority of New York and New Jersey (PANYNJ), located in hangar 17 at JFK airport, only 6 whole pieces, and portions of a further 6 pieces were shipped to NIST's location in Gaithersburg and "catalogued" for NIST’s WTC investigation. NIST does not attempt to justify the exclusion of so many pieces of saved WTC steel from its investigation, but reports only that "NIST personnel visited the hangar and identified 12 additional pieces that were considered important to its investigation."13 No evidentiary justification is given why NIST’s personnel "considered" the bulk of the steel as not important. The two photographs below show the recovered WTC steel, held in hangar 17 at JFK airport. The large number of pieces that were recovered by PANYNJ, but not "catalogued" by NIST and thus excluded from having at least a chance to be examined, is not mentioned by NIST.
Photographs from http://www.panynj.gov/wtcprogress/wtc-9-11-steel.html
The recovered WTC steel constitutes physical evidence. It was NIST's duty to do what they claimed to have done, namely to perform an "[e]xtensive failure analysis of the recovered steel,"14 but NIST did not do so. NIST's decision to exclude most of the steel from being adequately examined, based on circular arguments in the case of the "catalogued" columns and perimeter panels, and without any evidentiary justification in the case of the PANYNJ steel, is one of the reasons that NIST's report does not comply on even a very basic level with what is widely accepted as good practice in science.
NIST's exclusion of a common examination method
Specifically for the WTC steel, NIST developed a paint based and microscope aided method of visual examination to screen perimeter panels and core columns as to whether they were subjected to high temperatures.15 (If paint is left on a steel member, the paint is examined if it shows a crack pattern typical for an exposure to temperatures between 250 and 650°C.) NIST substituted this examination for the common method of unaided visual examination of the steel (which is mainly based on examining the steel for deformations like certain kinds of buckling, bends, etc.)16 NIST's method is, per design, most likely useless on all those areas of a steel member that experienced temperatures above approximately 650ºC, and almost certainly useless on all those areas of a steel member that experienced temperatures above approximately 800ºC. As NIST reports, a scale forms from 650ºC upwards between steel and paint, and both are likely to fall off easily.17 Areas of columns that were heated above 650 or 800ºC were therefore highly unlikely to have any paint left. NIST would have been able to follow up on columns that had no paint left using other methods (paint loss can be due to various reasons), but NIST did not do this -- despite the fact that paint loss is interpreted by the common method of unaided visual examination as a sign of possible exposure to high temperatures, and despite NIST’s explicit knowledge of the fact that the paint will indeed be lost from 650ºC upwards.
Given that NIST selected only four of the 55 columns that are discussed in paragraph 4.1 "CORE COLUMNS", NIST NCSTAR 1-3C, and 21 of the 90 panels to be screened as to whether they were subjected to high temperatures,18 an inherent characteristic of the microscope aided method had the effect of being a limitation too -- one can notice indications for a possible exposure to higher temperatures only on such steel members that were selected to be examined. In contrast, the common method of unaided visual examination more or less "forces" one to notice (i.e., whether one wishes to recognize it or not) that certain steel members most likely experienced high temperatures, and works also well for steel members that have no paint left.
For someone who wants to exclude evidence for exposure to high temperatures that has the potential to falsify NIST's premise, the limitations of the paint-cracking method are clearly advantageous. In fact, NIST went to great lengths to substitute its paint based method for the common method of unaided visual examination of the steel and to safeguard the exclusion of the common method. A contractor report where the common method was used was artfully "reviewed" so that NIST was able to act and write as if the common method would not exist as a useful method to screen columns and panels, and additionally, so that NIST did not need to follow up on certain pieces, including buckled columns from outside the impact and fire areas.19
By excluding in this deliberate way the data that the common method of visual examination can provide in respect to high temperature exposure of steel, NIST is again (i.e. independent of the above problem of the exclusion of steel) not in line with basic requirements of the scientific method.
Providing data for the validation of the temperature models and for the validation of "modeling efforts" of the "collapse analysis" was among the stated goals of NIST's steel examination.20 But NIST cannot have data of sufficient quality to validate the temperature models they developed and applied for the fire areas. The paint based method fails above 650ºC and NIST did not follow up on parts like core columns C-88a and C-88b, and on all three columns of panel S-10 where the paint method yielded "no conclusion" as "results" because no paint was left.21 This means that NIST's Twin Tower "how the point of collapse initiation was reached" computer models, which are at the core of NIST’s presented results, were run by NIST without any adequate validation of their temperature input-data.22
In addition, the named models were run without adequate validation with respect to the "fracture and failure behavior" of the steel in the models too -- at least when one wants models that are not bound by a premise that allowed only the consideration of the "fracture and failure behavior" of those steel pieces that were directly compromised by the airplane impact.
Two examples: core column C-30 and perimeter column K-16
One example of the effect of NIST's exclusionary tactics and of the poor quality of their investigation is the failure to adequately examine core column C-30. The as-built location of C-30 was in WTC 2, stories 104 to 106,23 at the north-east corner of the core. The column displays obvious signs indicating that it was bent at high temperatures and while it was still restrained in a frame. But C-30 was located far above the fire areas, and following up on these indications had the potential of falsifying NIST’s premise. Both the circular argument described above (which excluded C-30 from any examination regarding its damage and failure mode) and the exclusive use of the newly developed paint-based method "allowed" NIST to act as if they did not notice the obvious indications of possible high temperature exposure of C-30 while restrained in the frame. Any institution conducting a real investigation into the reasons for the destruction of the Twin Towers would have found the damage and failure modes of C-30 very interesting, at least for the reason that it stretched over those stories where the top part of WTC 2 started to disintegrate for no apparent reason early in the final destruction. The edge of the building showed a "sharp kink"24 in the south-east corner well above of the impact and fire area that degraded "into a gentle curve" in the north-east corner.25 The kink and the curve are documented in NIST NCSTAR 1-326 (i.e. in the part concerned with the steel examination.) The authors of the final report concerning the steel examination even expected that NIST would publish a discussion of the kink by T. McAllister (co-leader of Project 6 "Structural Fire Response and Collapse Analysis) as part of the final report,27 but they nevertheless neglected to examine C-30 for its damage and failure modes.
NIST was not able to apply its exclusionary tactics in the case of a heavily corroded perimeter column that was built-in well below the impact and fire areas; the piece was described already in Appendix C of the FEMA/ BPAT report that called for a more detailed study.28 NIST's metallurgical examination showed that the column, which also has an unusual corrosion scale containing iron sulfides and other compounds,29 must have been exposed to "much higher temperatures" than the "range from 700ºC to 800ºC" assumed in Appendix C.30 Even had there been office fires far below the impact and fire areas next to K-16, they would not have had much of an effect on K-16, because its fireproofing could not have been damaged by the airplane impact. NIST assumes that K-16 was affected by the high temperatures in the piles.31 But a mix of unburnable construction materials and dust covered, shredded office contents cannot sustain fires that burn hot enough to explain the high temperature exposure of K-16. This problem is not acknowledged by NIST, which treats the "incident scene" as not relevant for its investigation.32 But all available data -- including all data from the "incident scene" – are supposed to be collected and discussed, a fact of which NIST, which co-operates closely with the NFPA, and participates in the Technical Committee that develops the statements in the NFPA 921, is certainly aware.
Writer's note: I want to say thank you to Richard Zehnle from the AE911Truth Writing Team, who helped correct the English grammar and style.
1The full-length article can be found here: How NIST Avoided a Real Analysis of the Physical Evidence of WTC Steel (PDF)