April 28, 2007

Introduction

In September 2005, the National Institute of Standards and Technology (NIST) released a report on its "building and fire safety investigation to study the factors contributing to the probable cause (or causes) of post-impact collapse of the WTC Towers (WTC 1 and 2) and WTC 7". The report, NCSTAR 1-2, detailed the results of several computer analyses on the effect of the damage to the towers as a precursor to their collapse.

NIST NCSTAR 1-2: Baseline Structural Performance and Aircraft Impact Damage Analysis of the World Trade Center Towers, Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster

"The damage from the impact of a Boeing 767 aircraft (which is about 20 percent bigger than a Boeing 707) into each tower is well documented in NCSTAR 1-2. The massive damage was caused by the large mass of the aircraft, their high speed and momentum, which severed the relatively light steel of the exterior columns on the impact floors. . . . [This] supports the premise that the structural damage to the towers was due to the aircraft impact and not to any alternative forces." (from their FAQ)

As an interested citizen, the son of an engineer, and a very-part-time programmer at a structural analysis software company (LARSA) which happens to be similar to one of the applications NIST used in their analysis, I wanted to get a peak at the computer models used. I'm no conspiracy theorist, but I do like to go to the source when there's a debate.

In late September 2006, seeing that NIST had not posted their computer models publicly, I sent a Freedom of Information Act (FOIA) request to NIST asking that they make the files available to me. (I was not the first to do so, but at least the first to make it to the end of the process---thanks to the advice from the previous attempter---and post the files publicly.) Our government has very fortunately committed itself to making its records public when there is no compelling reason otherwise. In late April 2007 I received a CD from NIST containing the SAP 2000 (input) model files they created. (They used other programs and have other models. Since I was only familiar with SAP 2000 models and wanted to narrow the scope of the request to make it more likely to be filled in a timely manner, I only requested the SAP 2000 files.)

Under the FOIA law, NIST may in certain circumstances charge for the time spent on processing the request. They charged $58, classifying my request as commercial, which was very reasonable. You can see my FOIA request letter (with my contact info removed) which was based on NIST's FOIA guidelines.

The Files

The model files I requested are reference models of WTC 1 and 2, and do not model structural damage. From NIST NCSTART 1-2A, page iii, this component of the report was the

"Development of reference structural analysis models that capture the intended behavior of each of the two towers using the generated databases. These reference models were used to establish the baseline performance of the towers and also serve as a reference for more detailed models for other phases of the investigation, including aircraft impact damage analysis, and thermal-structural response and collapse initiation analysis. The main types of models developed were:

"− Two global models of the major structural components and systems for the towers, one each for WTC 1 and WTC 2. The models included all primary structural components in the towers, including exterior walls (columns and spandrel beams), core columns, exterior wall bracing in the basement floors, core bracing at the mechanical floors, core bracing at the main lobby atrium levels, hat trusses, and rigid and flexible diaphragms representing the floor systems.

"− One model each of the typical truss-framed floor (floor 96 of WTC 1) and typical beam- framed floor (floor 75 of WTC 2). The models included all major structural components in the floor system, including primary and bridging trusses, beams, strap anchors and horizontal trusses, concrete slabs, and viscoelastic dampers."

Original SAP 2000 .sdb Files from NIST:

The files from NIST were in the binary SAP 2000 project file format. These are completely no use to you unless you have a recent version of SAP 2000.

Floor_96_A_14_Jul_04.zip 4.3M

Floor_75_B_09_Jul_04.zip 948K

TowerA_02Sept04-SDB.zip 8.1M

TowerB_02Sept04-SDB.zip 7.3M

The two Tower files don't open in SAP 2000 version 10, but apparently do in version 11. The two Floor files open in version 10.

Other Formats

I converted the two Floor files (the ones I am able to open myself with SAP version 10) to DXF format:

Floor 96 A: DXF

Floor 75 B: DXF

It is my hope to post the models in other formats as I am able to. Any outside help would be appreciated.