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NIST Final Report on the Collapse of the World Trade Center Towers, Sept. 2005
Part II: Reconstructing the Disaster (chapters 5-7)
PDF pp.99-172 (NIST page numbers 49-222)

chapter 5: The Design and Construction of the Towers

1. According to Local Law 5 (1973) and Local Law 86 (1979), was compartmentation required in large, unsprinklered, upper stories of buildings that were built prior to the law's adoption? And were fully sprinklered buildings exempted?
2. In general, did the WTC design reflect typical building code standards in place at the time?
3. Were the WTC towers built to Class I-A or Class I-B standards, and did the Building Code specify which choice was required?
4. What was the basis for determining the thickness of the sprayed-on fireproofing used for the floor trusses?
5. When were sprinklers installed in the towers, and were the towers fully sprinklered in 2001?
6. What were the three main impacts on fire stairs when the 1968 Code superseded the 1938 version?
7. How many detectors, pull-stations, and monitors were installed after the 1993 bombing?
8. How was water connected to the sprinkler system in each of the WTC towers?

1. How many fires were reported in the WTC towers between 1970 and 2001? Of these, how many activated sprinklers or required use of standpipe hoses?
2. How long did the evacuation of the WTC towers due to the 1993 bombing take?
3. Why is it that a DCR (demand-to-capacity ratio) greater than 1.0 does not imply failure?
4. According to the conclusion reached on p.199 (NIST p.149), is it likely that the towers would have collapsed if sprayed-on fireproofing had remained intact after the impact of the planes?

1. Of the 8 factors that were correlated with enhanced life safety on p. 222 (NIST p. 172), which were the direct or indirect result of building code requirements, and which were the result of other considerations.

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