BY 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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This beam is made up of planks glued together. The industry calls this “engineered wood”; all wood products that are not simply sawn from a log could be called “engineered wood.” The industry brags that this wood only chars un-der fire conditions that would cause a steel beam to fail; it neglects to mention that many, possibly most, of the beams are supported on unprotected steel columns and are often connected with steel ties.
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Laminated beams can be formed in shapes such as these curves. A fire spreading across this polished ceiling is best fought by smooth-bore streams that can reach the ceiling and, so to speak, “fireproof” the wood.
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Commonly found in churches, these laminated timbers are formed into arches or rigid frames. Such arches are most often tied together foot to foot with steel rods. If the church is built on a slab, the rods are buried in the slab. If there is a basement, the rods may be ex-posed to a basement fire, causing them to weaken or come loose, and the arches are likely to collapse. (BCFS3, 74-78)
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Plywood delaminates. The layers come apart, thus the burning surface area and the intensity of the fire are increased. (BCFS3, 114)
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This is oriented strand board (OSB), chips of wood glued together. If someone were to burn comparable strips of OSB and conventional plywood to determine if there is a significant difference in burning characteristics, I would be happy to hear of the results.
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This is chipboard, which has been used for flooring in some trailers. A St. Mary’s County, Maryland, firefighter went through the floor as the water-soaked chipboard collapsed. This loaded sample collapsed in a couple of minutes.
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This is a flitch plate girder, a piece of steel plate sandwiched between two wood beams, which indicates that there is an unusually heavy load being carried. If the wood burns, the steel will buckle and the beam will fail. Note this hazard on the preplan.
Additional information the hazards of engineered wood can be found in Chapter 3, “Wood Construction,” under “Engineered Wood,” pp. 114-119, in BCFS3.
FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 60-year career to the safety of firefighters in building fires. He is 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 is an editorial advisory board member of Fire Engineering.
