Firefighting

Catastrophic hidden hazard

Issue 9 and Volume 154.

BY FRANCIS L. BRANNIGAN, SFPE (Fellow) Well, it’s not really hidden, but it might as well be unless all your firefighters can recognize the hazard immediately and operate defensively. The photo at right shows a posttensioned concrete building. There can be one or more floors that are hard, dry, and may be walked on but that are not connected to the columns! If a fire damages the gravity resistance system (GRS), the floor (which is a mass of concrete) will collapse on the floor below. No concrete floor is designed to sustain such an impact load, and the floors below will successively pancake. The first safety measure is to update the status of all concrete buildings under construction every day. Failing that, all personnel (down to the rookie) should be trained to recognize this hazard. The left arrow in the photo indicates a cable sticking out of the concrete. This…

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