7 World Trade Center collapse report released
NIST released today a draft of the final report on the collapse of 7 World Trade Center. The NIST investigation involved extensive computer modeling to simulate what happened, along with use of eyewitness accounts, photographs, video, and other evidence. The key findings include that the fire, fueled by office contents, and not fought (due to severed mains and lack of water), was the main cause of the collapse. Fires continued to burn throughout the afternoon on floors 7-9 and 11-13. Eventually the heat from the fire caused a critical column on the 13th floor to buckle. This triggered failure of structural elements surrounding the column, including the floor structure above to fail. This all led to a progression of the structural failure, vertically to the roof, and then horizontally across the structure and ultimately the entire structure collapsed. NIST rejected any blast scenario, explaining that if it happened, the sound would be so very loud and couldn’t be missed. However, there were plenty of witnesses around at the time, as well as news and other video footage. Any such sounds of detonations were definitely not there. In my experience, from seeing actual controlled demolitions, the charges are detonated in a quick succession over a period of 10+ seconds and are extremely loud and you do feel the vibrations. None of that occurred with WTC7. Anyway, the final report includes a summary 115-page report (PDF), along with detailed reports. There is also an FAQ and other material. NIST has given a few weeks as a public comment period, and will come back after that with a final version of the report.