Preplanning Building Hazards
FRANCIS L. BRANNIGAN,SFPE (FELLOW)
Editor`s note: For further reference, consult Building Construction for the Fire Service, Third Edition (BCFS3). Page numbers, where applicable, are included after the caption.
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One of the features of recent residential construction is the “great room” with a large floor area. The clear area may be achieved by a lumberyard of trusses, as seen here. How many fire-vulnerable gusset plate connectors do you think are in this photo? The failure of one gusset plate may cause total collapse by overloading connections near failure (as discussed in Preplanning Building Hazards, December 1997).
Interior firefighters may see only light smoke. Personnel outside must be alert to heavy smoke coming off the roof. All should appreciate that interior firefighters are then in imminent peril. Ventilating the roof will increase the fire and speed collapse. Pulling the ceiling has had the same effect. There is no obligation or tradition that requires firefighters be killed or injured fighting a fire in a building “built to collapse.” We must rethink tactics. The same design objective may be achieved by a “flitch plate girder,” composite wooden beams sandwiching a half-inch steel plate (shown in Preplanning Building Hazards, February 1998). If the wood burns, the steel will buckle and fail. UNDRESS THE BUILDING.
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This balcony is cantilevered. A cantilever is like a seesaw balanced on a support. If the interior part of the beam is damaged, the balcony will fall. The approach to a serious fire involving the floor should be through the wall from an uninvolved unit, not from the balcony. (BCFS3, 56)
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Steel girders have long been used in otherwise wooden structures. Note the extra flange extruded on this steel girder to support the wooden floor beams. There is no connection. Sufficient heat (not a terribly high level–particularly if the heat is confined, as it would be here) would cause failure and the floor to drop out from under firefighters. (BCFS3, 314-317)
FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering`s first Lifetime Achievement Award, has devoted more than half of his 57-year career to the safety of firefighters in building fires. He is well known for his lectures and videotapes and as the author of Building Construction for the Fire Service, Third Edition, published by the National Fire Protection Association. Brannigan is an editorial advisory board member of Fire Engineering.
