Originally posted by twitchy
Originally posted by HowardRoark
Modern steel buildings are designed to withstand fire for 4 hours.
WTC 7 burned for 7....
This is perhaps the most ignorant thing you have posted so far. There are cases of "Modern steel buildings" burning for three and four days without
collapse. Spin on Spin Doctor! Also an order was given to "Pull" WTC 5. Another matter of public record which raises an interesting question about
how they intended to do that without already having some way to do it planned and implemented as it fell shortly there after. LOL four hours. Guess I
need to change my engine block in my car every four hours then.
No, that is the most ignorant thing you
First of all, it is a fact that building codes only call for a four hour fire resistance. This is applied to a variety of building materials. from
drywall assemblies, to doors, ceilings and yes fireproofing.
What exactly is fireproofing? is it there to prevent the building from burning? No, structural fireproofing is insulation. The entire purpose of
structural fireproofing is to insulate the structural members from the heat of a fire. if a fireproofing is rated for 4-hours that means that it will
protect the structural member from the fire for 4 hours, after which, of course, there is no protection, and the structural component is subject to
What do I know about fireproofinig? Well I spent about ten years designing and managing asbestos abatement projects to remove and replace
fireproofing from a number of high-rise buildings.
There are more different types of fireproofing then you can possibly imagine. Often a typical building will have several different types reflecting
different construction phases, renovations and even from changes in contractors in the progress of building construction.
Older building from the 20's, 30's and 40's generally have non-asbestos fireproofing. The beams and columns of these buildings are usually encased
in masonry such as clay tiles or Pyrobar blocks. In the 50's you sometimes see a sort of vermiculite plaster applied over a wire lath. The mid
50's through the early 70's was the heyday of sprayed on asbestos fireproofing. This material was mixed in the field and sprayed onto the steel
with an air powered spray gun.
There were many different manufactures and because the spray was mixed in the field, there can be any number of different forms of the sprayed on
materials. Some are light and extremely friable. The slightest touch is enough to dislodge the stuff (this is the real nasty stuff that was
responsible for a number of asbestos related diseases among the workers who applied it). Some formulations have high vermiculite content, others are
very cementicious. the stuff is literally like concrete and is a bitch to remove. In some cases, the contractor used too much water in the mix,
resulting in poor adhesion of the fireproofing to the substrate.
Regardless of what particular formulation was used, one thing I can tell you with absolute certainty, floor joists of the type used in the WTC are
almost impossible to spray properly. The thin cross section of the joist components and the open webbing, meant that most of the spray misses the
joist entirely and winds up on the deck or the floor. Furthermore, the intricate pattern of diagonals is impossible to cover with any regularity.
Usually only the the top and bottom chord get sprayed properly, and even then sometimes only the bottom portion of the bottom chord.
The fireproofing is sprayed on first, then the other trades will come in and do their thing. What do you think the pipe fitters, plumbers, tin
knockers, electricians, sprinkler fitters, etc, do when they want to hang something in the ceiling plenum? they scrape a section of the fireproofing
off the beam or joist and attach a clamp to it. The General Contractor is supposed to go back and patch all of those scrapes, but when you have a
30" duct and a bunch of conduit in the way, it almost never gets done properly. If the floor is later renovated with extensive retrofit of the
electrical system and the ducts, replacement of the fireproofing is never addressed.
In addition, I have seen a lot of buildings where it was clear that shortcuts were taken during construction. Beam connections missing bolts, areas
not fireproofed, concrete decks with too much chloride, sagging floors, sagging roofs, cracked bearing walls, etc.
Yes, there have been a couple of building that suffered catastrophic fires and did not collapse. BUT, trying to compare them to any other building
like the WTC 1, 2, 5, or 7, is like comparing apples to oranges. First of all, none of those other buildings suffered structural damage like the WTC
buildings. None of them was designed or built the same. Even the overall shape of the building such as the ratio of the width to the height has to
be considered. The style of construction is guaranteed to be different, the types of fireproofing used, the thickness of the floor slabs, the wind
resistance and strength of the windows, the floor loading, all of these things have to be considered.
Additionally, due to changes in business practices and interior office designs over the last ten years, the fuel load of an office in 2001 is totally
different from the fuel load of an office as recently as 1990.
Therefore, your attempt to lump all steel framed high rises into one catch all category is simply wrong.
That is kind of like saying that because a SAAB survived a rear end collision without catching fire, then your 1973 Ford Pinto is safe in the same
sort of accident.
This, dude, is simply flawed logic.
Guess I need to change my engine block in my car every four hours then.
First drain all of the coolant out of the engine and then see how long it will run.