BOF FF2 Chapter 2*17 Building Materials, Structural Collapse, and Effects of Fire Suppression

Collapse Zone

Area beneath a wall in which the wall is likely to land if it loses structural integrity.

Curtain Wall

Nonload-bearing exterior wall attached to the outside of a building with a rigid steel frame. Usually the front exterior wall of a building intended to provide a certain appearance.

Drywall

System of interior wall finish using sheets of gypsum board and taped joints.

Fiberglass

Composite material consisting of glass fibers embedded in resin.

Green Wood

Wood with high moisture content.

Gypsum

Fire-resistant material used for gypsum plaster and wallboard.

Heating, Ventilation, and Air Conditioning (HVAC) System

Mechanical system used to provide environmental control within a structure, and the equipment necessary to make it function; usually a single, integrated unit with a complex system of ducts throughout the building.

Rebar

Short for reinforcing bar. These steel bars are placed in concrete forms before the cement is poured. When the concrete sets (hardens), the rebar within it adds considerable strength and reinforcement.

Structural Collapse

Structural failure of a building or any portion of it resulting from fire, snow, wind, water, or damage from other forces.

Veneered Walls

Walls with a surface layer of attractive material laid over a base of a common material.

What characteristics of wood affect how it reacts to fire conditions?

The characteristics include the wood’s moisture content, natural-old/farmed-new, density, and size (bigger the better).

What is spalling?

stones and concrete may loose small portions of their surface when heated

What happens to steel and aluminum structural members when exposed to heat?

Steel elongates/lengthens when heated, pushing the walls out and buckles, possibly pulling the walls in; aluminum is affected more quickly by heat - it takes more energy to heat but melts at a lower temperature, so it fails faster

How does reinforced concrete lose its strength in fire conditions?

Through spalling, where failure of the bond between the concrete and the steel reinforcement cause cracks, where the strength may be reduced

Which building material has excellent heat-resistant and fire-retardant properties because of its high water content?

Gypsum board has chemically bound water, which absorbs heat

What happens to glass that is exposed to excessive heat?

may crack or shatter when a cold hose strikes the glass, materials may also be combustible and difficult to distinguish

What hazards are associated with Type 1 of building collapse?

not likely to collapse, hazard of flying glass or debris from windows/certain walls, contents might burn, and structure collapse would be localized

What hazards are associated with Type 2 of building collapse?

the unprotected steel or noncombustible I Beam supports expands and twists, pushing out walls until water cools and constricts, causing movement for walls and floors to collapse especially brick and block walls supporting unprotected steel bar joists/I Beams

What hazards are associated with Type 3 of building collapse?

these exterior load bearing walls made of concrete, brick, or masonry and interior loads made of wood, masonry, and unprotected steel can collapse in one piece or crumble and debris can travel some distance, causing collapse of other structures/objects

What hazards are associated with Type 4 of building collapse?

this heavy timber or mill construction is least likely to collapse, unless the weight bearing capacity of the large dimension wood members are affected by a large volume of fire

What hazards are associated with Type 5 of building collapse?

may collapse inward or outward, *plan for a collapse zone, exterior masonry and veneer walls can fall straight down or out (although this is more rare), often resulting in collapse in 10 min *very early in the incident

How does the length of fire exposure affect the risk of collapse?

the higher the heat release rates, the greater the damage to structure and risk of collapse (affected by size, compartmentalization, construction type, fuel load, materials)

What are some indicators of structural instability and collapse?

roof sagging/pulling away/spongy, floors saggy/spongy, fire involved in trusses/structure, ceiling/plaster pieces falling, movement of walls/floors/roof, noises by structure, little to no water runoff, cracks in exterior with smoke/water appearing, presence of tie rods through walls, loose/falling bricks, deteriorated motar between masonry, leaning walls, distorted structure, fire beneath heavy supporting floors, prolonged fire to structure, structure pulling away from walls, excessive weight of building contents

Where should a collapse zone be established?

adjacent to any exposed exterior walls; about 1.5 times the height of the building unless this is impractical and limits defensive firefighting

What actions should be taken if collapse is imminent?

As your crew exits, inform command; establish a clear collapse zone - no personnel or apparatus; conduct role call or PAR

What are some building conditions that contribute to fire spread?

Construction type and elapsed time of structural integrity, fuel load of structual members and contents, building compartmentation, construction features, and construction/renovation/demolition hazards

How can the amount of water used to suppress a fire affect structural components?

direct effect on an unstable structure, adding 8 pounds per liter of water, adding to weakend floors, causing floors to pancake, pushing walls out, or complete failure