BY FRANCIS L. BRANNIGAN, SFPE (Fellow)
Fairfax County, Virginia, had a fire that started on a rear deck of a townhouse and communicated to exposures on both sides.
In Montgomery County, Maryland, a burning porch collapsed on a firefighter. The porch was lag bolted to a ledger board and thus appeared to be substantial, but the ledger board was not adequately attached to the house.
A few years ago, a porch in Prince George’s County, Maryland, collapsed under the weight of several people. The “sturdy” ledger boards had been nailed into the ends of 2 2 2 top-on-bottom flanges of the wooden I-beams. The same was true for all the houses in the development.
A Maryland builder had left a candle burning in a wicker basket on the deck. The fire involved the entire side of the house and penetrated the interior before a neighbor notified the builder of the fire. The house was a total loss. Mirabile dictu (marvelous to say), the new house will be sprinklered. Does anybody know of other builders who have sprinklered their houses?
Almost all porches are built of lumber treated to resist rot and insects. When such wood burns, the smoke is very toxic. Normally, personnel operating at such a fire would not wear SCBA. It is most important that personnel extinguishing, overhauling, or investigating a fire in such a deck wear SCBA.
A row of townhouses with combustible exterior finish and those delightful (to the fire) attic vents on the underside of the soffit may have a continuous run of decks on the difficult-to-access rear. Unless you have studied and preplanned, there is a good possibility all the units will go. I say “all the units” because that is how you would describe them. In my opinion, we should think of the whole group as one building. That is how the fire thinks. There is no effective separation if the fire involves the back porches. A few propane cylinders will probably add to the excitement.
How would you get a big line that supplies a manifold feeding several small lines to the fire? The problem here in many cases would be not enough firefighters. How about calling a neighborhood meeting to explain the problem and show the residents how they can help to stretch the line? If you should have to stretch such a line and were obviously shorthanded, citizens would be lending a hand. A little training might make the operation more successful.
FRAUDULENT ENGINEERING
Some years ago, several workmen died in the collapse of a concrete building under construction. The investigation disclosed that the building code required an engineer’s stamp. The department could not afford to hire the necessary expertise to check the plans; the builder hired a retired engineer who approved the plans without ever studying them.
The New York Times (June 13, p. B3) tells of corruption involving building permits. A politically connected “consultant” used a retired engineer’s official seal to stamp 150 plans the engineer had not seen. I wonder if anybody is looking at these 150 buildings to see what flaws might exist.
CARDBOARD STORAGE BOXES
In reference to Jeff A. Welch’s “Just Another Warehouse Fire? No Such Thing,” What We Learned, Fire Engineering, August 2000, do you have a record storage facility in which records are stored in cardboard boxes? Do you know that the boxes may present a sulfur hazard? Do not wait for a fire. Get in touch with the manufacturer and get the MSDS. The boxes probably have been impregnated with sulfur for preservation.
LAMINATED TIMBER BEAMS AND ARCHES
The industry often cites that heavy laminated wooden beams are resistant to fire, but note that most of the beams are supported on unprotected steel columns. If the column appears to be timber, check to see whether it is really timber or just a wooden box around an unprotected steel column. Every element of the gravity resistance system (GRS)-beams, columns, and connections-is vital. If the weakest component fails in a fire, the entire system fails.
Laminated timbers are plank-like sections of nominal two-inch (or even thinner) boards glued together under pressure to produce large arches, beams, girders, and columns. Such timbers are also known as “Glulam.” (Bolts are sometimes used to supplement the glue.) When highly finished, these timbers are most attractive. Combined with wood plank, they can provide the necessary structural strength and an aesthetically pleasing interior finish.
Laminated wood sections were spliced together to form arches for a Daytona Beach (FL) jai alai fronton (a sports arena). The wood was only charred, but the arches fell apart at the metal connections.
In the days of wooden ships, shipwrights sought out trees that had grown in the special shape required for certain structural members. Today, almost any shape can be fabricated by gluing.
We usually think of arches as having the segmental “arch” shape. There are other shapes. The key element in an arch is that the arch-whatever the material-is always in compression. The thrust is outward. Older trusses were built with masonry buttresses to resist the outthrust. “Two-hinge” arches of laminated wood are available; they combine column and girder in one member and provide a straight-walled structure with a flat roof and a clear floor area. The Forest Products Laboratory in Madison, Wisconsin, is constructed of arches that provide a floor area the equivalent of a five-story-high, 60-foot span. Laminated timbers apparently burn like solid timbers and do not delaminate like plywood.
Beams or arches spliced with steel connectors should be noted on prefire plans. It may be possible to protect the splice area with hose streams. Collapse is a serious factor.
The jai alai fronton in Daytona Beach burned. Everybody sued everybody else. The owners sued the makers of the foam plastic insulation on the roof. Their argument: “Your flammable plastic overcame the stability of our sturdy heavy timber building.”
I had pictures that showed that fire-vulnerable metal strap connectors had simply disconnected as the hot bolts destroyed the wood fibers holding them. I was an expert for the defense. When the plaintiffs found out that the defense had these pictures, they folded. The late Chief Franklin of the Silver Spring (MD) Fire Department had given me the picture. (Building Construction for the Fire Service, Third Edition, page 80)
Many churches have wood arches without the masonry buttresses. These arches are tied by steel rods, which connect the ends. The fire-vulnerable steel ties are located in the basement ceiling. If there is a basement fire, the elongation (steel industry likes the term “relaxing”) of the steel might cause the arch to fail.
If there is a concrete floor, on the ground, the tie rods are imbedded in the floor. In the case of large steel arches in aircraft hangars, the rods are encased in a heavy concrete cover to prevent their being cut in a floor renovation.
A NEW TECHNIQUE: UPDATE
A new technique for increasing the carrying capacity of beams is to reinforce panels of plastic with carbon fibers. We don’t know anything about the plastic panel’s fire characteristics except that it is probable that the plastic panels would fail in a fire and the beam would revert to its original carrying capacity. I have heard of steel, and possibly concrete, beams being reinforced in this manner. Peter McBride of the Ottawa, Canada, Fire Department is following this matter. If you have this type of construction in your area, send information and pictures to [email protected].
THE WORLD TRADE CENTER DISASTER
Below are the sentiments I expressed on fireengineering.com:
We must learn to think the unthinkable. When I first postulated the total collapse of a post-tensioned concrete building under construction at a 1971 National Fire Protection Association meeting, the editor of a fire journal refused to print it, saying, “I just can’t believe they are building buildings that will completely collapse.”
We must go beyond EXPERIENCE to competent risk analysis. We must learn that “fire resistance” is at best just a hope, not a mathematical given, as is often assumed. We must learn that the failure of a single vulnerable connection can precipitate disaster.
I have been in love with FDNY for 75 years. My first line-of-duty funeral was for the eight firefighters who died in the unsprinklered paint room of a spare-no-expense hotel in 1932.
May they all rest in peace. May their families and friends take comfort in the Biblical verse: “Greater love no man hath than he lay down his life for a friend.” How much more loving to lay down one’s life for a stranger!
FRANCIS L. BRANNIGAN, SFPE (Fellow), recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 59-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.
