It was a cold and damp afternoon on Wednesday, April 24, 1996, in Tonawanda, NY, north of Buffalo. Just after 4 P.M., Andrew Farber, an employee of a demolition company, was preparing to make the last cuts to bolts securing the structural steel columns on the first floor of the former foundry...
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The fire was in a 102-year-old Odd Fellows Hall. The building was 3 1/2-story ordinary commercial. Pre-planning had disclosed that there were two large light weight steel trusses in the cockloft, running from front to rear.
Responding units found fire on the second floor rear and heavy smoke and heat on the third floor.
An aggressive interior attack was initiated BUT "all sector and division commanders were ordered to monitor the attic and report to command any fire in the cockloft. Simultaneously the roof sector, rear sector and two interior divisions reported fire in the exterior defensive attack was undertaken. Shortly after one truss collapsed dropping the roof into the third floor. A massive fireball extended 40 to 50 feet into the sky."
The letter closes: "I would like to thank you for your efforts over the hazards of truss roof construction. It is this knowledge that clearly averted a tragedy."
Know Your Buildings!
- In the 1970s, four firefighters died in the collapse of a steel bowstring truss in an automobile dealership in Wichita, KS.
- Six Dallas firefighters were pitched into a fire when elongating bar joists pushed down a concrete block wall. Fortunately, they were at the edge of the roof and could be recovered rapidly.
- Two fire officers in the Midwest barely escaped a bar joist collapse. One was about to step onto the roof when it went in. The other, concerned about the trusses, withdrew his unit just in time. In both the preceding cases the insulated metal deck roof was on fire (if you don't understand this, read Building Construction For The Fire Service, third edition, pages 302-309). It is impossible to vent a metal deck roof adequately and safely. Tests showed that a 64-square-foot vent would be required in a building only 20 feet wide, in which only the roof was on fire.
- Huge steel trusses in Chicago's McCormack Place were destroyed in 45 minutes by a tremendous fire load of combustible contents. Fortunately, the hydrants were shut off and entry was providentially delayed.
Tests at the National Bureau of Standards (now the National Institute for Standards & Technology) compared steel bar joists with two-inch nominal wood beams. The wood beams failed in 10 minutes, the steel bar joists in seven.
Steel Is A Thermoplastic Killer
On page 230 of Building Construction For The Fire Service, third edition, I show an apartment house with a large steel beam holding up a substantial load and point out that a fire might cause it to fail. I understand that such a beam failed in a fire in Gwynn County, GA, and cost a firefighter his life. We simply cannot rely on experience, which is blood, sweat and tears.
Four Pennsylvania volunteers died when unprotected steel columns supporting a concrete floor melted. The floor opened up and they fell into the fire. We must become more competent at recognizing death traps before they spring.
A most important use of water at a fire where structural steel is involved, is to cool the steel. Do not believe myths about water causing steel to fail. Structural steel fails at about 1,100 degrees Fahrenheit. Cooling failing steel simply freezes it in the distorted position (see Building Construction For The Fire Service, third edition, page 259 for an IFSTA statement). A Texas fire department "threw the wet stuff on the red stuff" in a fire in a steel hay shed. The wet half burned hay was "saved." The steel structure was heavily damaged. Do note that cold drawn steel, such as tendons in tensioned concrete, excavation tie backs and cables generally, fails at 800 degrees F less than the temperature of a self-cleaning oven. Failure of a tendon in a T beam caused the loss of a Florida firefighter.
For further information about the hazards of steel, see Chapter 7 of Building Construction For The Fire Service, third edition. Call 301-855-1982 for information about the book.
By Francis L. Brannigan, SFPE