Engineering Analysis of WTC and Other Major Building Fires

Following is link by Engineering Department of Manchester University (UK)
of several major building fires and effects on building structures .

Included are Winsor Tower (Madrid) and First Interstate Bank (Los Angles),
two of the favorites by the tin foil crowd who frequently dwell on the fact
that "No building collapsed from fire".

Manchester University is a highly respected institution, also since is a
non US institution may (but I rather doubt it) quiet some of "inside job"
types who dismiss anything that doesn't feed into their particular
conspiracy fantasy as faked.

World Trade Center

www.mace.manchester.ac.uk...
Main Menu Page

www.mace.manchester.ac.uk...

Nice read. Thanks for trying to get the truth out.

Trying to get what truth out? The building didn't completely collapse. I'm not sure what you think you're proving out here, but I can assure you I'm not seeing it at this point.

Help me understand.

These aren't really any "engineering analysis," it's more like three short Internet articles hosted by a university.

Originally posted by thedman
Included are Winsor Tower (Madrid) and First Interstate Bank (Los Angles),
two of the favorites by the tin foil crowd who frequently dwell on the fact
that "No building collapsed from fire".

Anything in particular you trying to point out? Because the First Interstate Bank was a steel-framed structure that had a more severe fire and didn't collapse, and the website you link to even explains how minor the damage was, and how long the fire lasted and how many floors it spanned.


In particular, there is absolutely no mention of sagging floors deflecting exterior columns, which is what NIST concluded was the collapse initiation mechanism. Nothing else. And that building had the same composite floors, and (smaller) columns along the exterior in a (less-sturdy) grid.

Damage

The total burnout of four and a half floors did not cause damage to the main structural members due to a good application of spayed fire protection on all steelwork. There was only minor damage to one secondary beam and a small number of floor decks.

The non-structural damages included:

* Virtually all external cladding from the 12th to 16th floors was destroyed and fell to the ground.
* The heat of the fire caused some aluminium alloy valves in the occupant hose cabinets to fail, creating water leaks and causing water damage on floors below the fire.

I want to make a comment about the bolded statement. They do not try to support this claim with any substance, which leads me to believe that they're just assuming that this is what prevented failure. Another UK educational institute, the University of Edinburgh, actually did a study with some other groups on the effects of fire on steel frames (without fireproofing), and found that fireproofing wasn't actually necessary, and that redundant structures experience the most buckling and warping from internal stresses induced in the members from expansion due to heating. The primary failure mode at the relevant temperature range (uniformly heating bare steel to 600 C or lower) is not due to strength loss, but is buckling and warping due to internal stress, from the steel trying to stretch out but being held in place by other members. They recommended designs that allow for localized buckling and warping, to prevent stresses from spreading far outside of the more heated areas.

In either case, the WTC Towers had spray-on fireproofing as well (and tons of asbestos, and maybe even a concrete core wall), and there's no evidence that the impacts caused enough vibration to knock any of it off, outside of the steel that was most directly impacted. NIST actually did "tests" (I don't know what I would call them) where they shot at fireproofed members with a shotgun, and tried to say that this was comparable to vibrations induced by the impacts. The only fireproofing that came off in their experiment was the fireproofing right around where the steel was directly impacted with the shot gun blast, and the rest stayed on despite the vibrations. At any rate, just assuming that it all fell off is 100% as arbitrary of an assumption as assuming that they did not. And also in either case, steel has to be uniformly heated to a very high temperature before it's going to experience significant strength loss, and there's no science that suggests that this is a viable global collapse mechanism anyway in steel buildings. The UoE study even says that the failures induced from internal stresses tends to be localized, the immediate neighbors of the affected beam compensating for whatever loss has occurred.


The First Interstate Bank fire burned for 220 minutes, more than twice as long as either of the Twin Towers. Fire engulfed five floors (including the one it started one), and "destroyed" (the website's terminology, not mine) four of them. The building did not have a sprinkler system functioning. The WTC Towers also did not have a sprinkler system, and those fires also spanned 4-5 floors each.


See if this floor plan looks familiar:




It was a steel-framed building with light-weight concrete slabs used in the composite floors (sound familiar?). The columns in general were much smaller and fewer than in either of the WTC Towers.

A diagram of the fire:




Exterior damage:




Another view:




Inside of the building:




What's important to note is that the fire itself did virtually no damage to the actual steel structure. The plane impacts into the WTC Towers did all of the damage that was done to those buildings before they collapsed, and they only compromised less than 15% of the columns on the impacted floors, whereas there would've had to have been more like 50% compromised at the very least. You never hear about fire causing such damage to structures, outside of the WTC Towers and Building 7, to actually cause anything other than a very localized failure (ie simple buckling or warping, in one place, as observed in the smaller WTC buildings after they also burned for hours on 9/11).

[edit on 12-11-2007 by bsbray11]