BY FRANCIS L. BRANNIGAN, SFPE (Fellow)
Editor’s note: Francis L. Brannigan had submitted this column, and others, before his sudden death on January 10.
Below is my response to a question about concrete building fires from Lieutenant Mike Froelich of the Sylvania Township (OH) Fire Department.
This is so-called ‘tilt slab,’ or tilt-up construction.1 Formerly, slabs would be cast on the ground and then tilted up. Now, the finished slab is delivered on a truck.
The roof of such buildings is absolutely vital to the stability of the walls. The roof may be of steel bar joists, precast concrete, T-beams, or laminated wood timbers.
Concrete is inherently noncombustible but, unless required by code, is not made to meet fire resistance standards. So-called reinforced concrete is a composite of concrete for compressive strength and steel for tensile strength. If concrete spalls off and the steel is exposed, the composite is lost and failure is likely.
Those lovely laminated wood beams touted by the wood industry as ‘slow burning’ are held together by unprotected steel connectors and may have intermediate columns of unprotected steel. If it has a metal roof with bar joists, very probably it has a ‘built-up’ roof, which can provide a combustible metal deck roof fire.
There are many problems with high-rack storage in such buildings.2 Gaskets between wall units are neoprene, so fire can extend either way through the ‘concrete wall.’ A recent Los Angeles fire was described as originating outside the building and extending into it. [No information] was provided as to the [cause of the fire], but the neoprene gaskets are a good bet.
TACTICAL SUGGESTIONS
Position all apparatus outside the collapse zone on arrival. If hydrants are in the collapse zone, prepare to lay supply lines from the hydrant to the pumper. The first engine, no matter what, supplies the sprinklers to the max. Suppressing the fire is the best lifesaving technique.
Any such fire will present a huge mutual-aid problem. Form a committee of representatives who will probably assist, and formulate the plan. Bring a water supply. Police will be needed for traffic control.
If you have a CMDR [combustible metal deck roof] fire, the ladder pipe will be ineffective. The lack of openings to make a hoseline attack may make the “Brannigan Attack,” cooling the underside of the roof to cut off gas flow, impossible. If the building has a membrane roof, dripping fire may be a problem, but there is not enough heat to destroy steel.
Bring management into the process. Go directly to the head administrator. Stress the need for immediately notifying the fire department when there is a fire and for training employees in evacuation methods.
When discussing this problem, a fire officer told me that he was told that the walls were designed to fall inward. When someone talks like that, make a strong request for proof, or do not accept it. If the exterior is dressed up with brick veneer, the bricks may be a separate collapse hazard if the concrete is moved. Such veneers have fallen off concrete out of a clear sky.
Endnotes
1. See Ol’ Professor, June 2005, for a full discussion of this deadly hazard. For erection hazards and a specific fire, see page 357 of Building Construction for the Fire Service (BCFS3). See also “Tilt Slab Hazards,” page 373.
2. See pages 605-636, BCFS3. Also review the chapter on sprinklers, pages 565-604.
FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering’s first Lifetime Achievement Award, devoted more than half of his 63-year career to the safety of firefighters in building fires. He was well known as the author of Building Construction for the Fire Service, Third Edition (National Fire Protection Association, 1992) and for his lectures and videotapes. Brannigan was an editorial advisory board member of Fire Engineering.
