Written by Andrea Dreger
August 23, 2011

Editorial: 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.

That NIST’s investigation is not in line with the most basic requirements of the scientific method is demonstrated by a closer look at NIST’s examination of the steel, which was based on the premise that nothing other than airplane impact damage and the subsequent fires brought down the Twin Towers, and where the most relevant question – why did the strong steel frames below the impact area give way – is neglected. NIST cannot justify its failure to adequately examining the steel with its published results; examining the evidence adequately is a step that needs to be done at the beginning of an investigation.

(Abridged version)1
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 discuss 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 describes “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.

Link to the rest of the article How NIST Avoided a Real Analysis of the Physical Evidence of WTC Steel