Thread: concrete vs steel in fires?
09-14-2005, 07:44 PM #1
- Join Date
- Aug 2005
concrete vs steel in fires?
Does concrete resist fire better than structural steel? I was reading this thing about a skyscraper fire in Spain that burned for a long time, the building collapsed part way but not completely and it had concrete columns in it.
See it here: http://www.arup.com/fire/feature.cfm?pageid=6150
ETA: Wikipedia has another picture of it, and it looks like the tower collapsed around the outside.
The inside area that stayed standing is where the concrete columns were.
Last edited by KemalT; 09-14-2005 at 08:30 PM.
09-15-2005, 10:23 AM #2
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- Nov 2000
- Sitting on my Laa Laa waiting for my Yaa Yaa
Although it seems like a simple question, the answer is not so simple.
First of all, most concrete buildings have reinforcing steel in the concrete (concrete is good at resisting squeezing forces, not so good at resisting stretching forces, so steel is added to the concrete) so you don't have a "pure concrete" building.
Concrete members appear to be more fire resistive at first glance because they are usually larger than a steel member and they take longer to heat up (they can absorb more heat) before they show distress. However, when they get hot enough, the water that is contained in the concrete (and there is always some) can turn to steam, expand, and cause an explosive spalling of the concrete member that could lead to a sudden failure. Generally, sudden failures are something that is undesirable.
Steel members are generally smaller in cross section so they absorb heat and reach the point where they fail at a faster rate. That is why you see "sprayed on" fire proofing or concrete encasement of steel framing in buildings that contain a significant life hazard. However, when a steel frame begins to fail from exposure to fire, it usually sags and gives you some visual clues that it is getting ready to fail, so you have a little bit of time to get the heck out of dodge.Chris Minick, P.E., Firefighter II
Structures Specialist, MD-TF 1
These statements are mine and mine alone
I.A.C.O.J. Building crust and proud of it
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