Post-tensioned concrete cutting hazards
Francis L. Brannigan, SFPE
Matt Szpindor`s “Valuable Rubble: Seizing Your Training Opportunities” (December 1998) mentions drilling through concrete and concrete coring drills.
Any mention of drilling through concrete or cutting steel reinforcement should be accompanied by the caution, “Determine whether conventional reinforced concrete or post-tensioned concrete is involved.” If it is the latter, no cutting or drilling should be permitted without full realization of the very serious hazards involved. Post-tensioned concrete has steel cable or rod tendons that are under tremendous tension to hold the concrete in compression. Cutting a tendon with a torch or core drill can release a tendon, which could whip around and kill anyone in its path. Would you cut a cable between a straining tow truck and the vehicle it is towing? The tendons in concrete are under far greater tension.
Demolition contractors are aware of the hazard, but the American Institute of Architects and the Post Tensioning Institute have rejected their request that post-tensioned buildings be placarded and a permanent set of plans be retained. We can wonder why.
We should be aware of every post-tensioned building in our area and train accordingly. Failing preplanning, be aware that steel cables are a sign of tensioned concrete, and act accordingly. Command should come to attention at any talk of “cutting cables.” For further reference, see pages 270-271 of Building Construction for the Fire Service, Third Edition.