A quick questio nabout the collapse

[R.Mackey]

Didn't the experience of the 1993 bombing result in upgrades to the exit paths?

Some of these issues were addressed or in work after the 1993 bombing.

To be more specific, however, see pp. 41-42, NCSTAR1-7.

 

[ElMondoHummus]

There's a direct comparison of building codes in NCSTAR1-1B, conveniently provided for you in tabular form...

Ha! Shows you all just how ill versed I am in the NIST report. I've even perused 1-1B and made reference to it in previous threads, yet I didn't know that.

I keep saying that I need to read the entire NIST report, but I keep failing... probably because my mind turns to mush after a few pages ... never said I had a mind amenable to reading engineering works.

Dr. Astaneh-asl, however, is correct to point out that the testing of the floor truss construction was inadequate, and if it had been properly tested, it would not have met the Port Authority-specific building code, or the New York City codes from which it was derived. The engineers who signed off on the tests did not recognize -- indeed, had no way to know -- that the floor trusses did not scale down to the tests that were carried out. Had the Towers been of a more conventional design, it is possible that the Towers would have stood longer or not collapsed at all, but there are far too many variables to state this with any certainty.

Astaneh-Asl was quoted in my above link as saying "so many violations of practice and code were introduced". Does anyone here know if his list is composed of the same deviations that NCSTAR 1-1, 1-1A, and 1-1B enumerated? I've been presuming that Astaneh-asl's complaints are indeed about the exemptions that were granted, but on rereading what sources I have on hand, I'm now realizing that it's not 100% clear. There's room for Astaneh-Asl to have been referring to other things when he makes the charge about "violations of practice and code".

 

[ElMondoHummus]

This gets a little strange, actually. What would become PANYNJ was not (and is not) required to comply with local building codes because it was "an interstate compact created under a clause of the U.S. Constitution" (reference NCSTAR 1-1B, Chapter 2, intro para.) and therefore is an authority unto itself. However, the Port Authority decided to have the architects and engineers use the New York City Building Code as a basis of design, except where the code was ambiguous or where technology made it obsolete, in which case the basis of design would be "acceptable engineering practice". So any exemptions requested by the design team would be awarded by the Port Authority, not the New York City Department of Buildings (the normal reviewer of building plans).

Interesting and perhaps relevant is the fact that New York City revised its building code during the design of the World Trade Center towers, switching from the 1938 edition to a completely rewritten code in 1968. According to NIST (NCSTAR 1-1B, Section 3.1, para. 2) the 1968 edition allowed for performance-based design, as opposed to the strictly prescriptive and empirical methods allowed under the 1938 edition. Had the Port Authority (and therefore the design team) stuck with the prevision version as a basis of design, one wonders how different the towers would have been, and if the horrible events of September 11th would have played out differently.

D'oh! I thought it was the NYC government that granted the exemptions. Shows you what I know.

 

[AZCat]

D'oh! I thought it was the NYC government that granted the exemptions. Shows you what I know.

It wouldn't seem like an important section to most people, but I've worked on projects with similar arrangements, so it stuck in my mind.