FFP PD Ch 6 LW Construction Flashcards
Fires in traditional PD of ordinary/wood frame construction, early collapse is not a primary consideration. Collapse occurs in about _. However, if structural components exposed failure occurs within _
1 hour;
20 minutes
PD constructed w/LW materials: Fires extended from building contents to structural components, collapse occurs within _
5-10 minutes with little or NO warning
Primary Consideration in PD’s w/LW materials
Collapse
Paramount Importance in PD’s w/LW construction
Positioning 1st HL for early extinguishment or control of contents fire that has NOT extended to structural components
LW construction: Areas unsupported by columns w/spans greater than _’ are generally indicators that LW construction present
greater than 25’
Most important factor to a safe & successful operation at LW construction fires
ID of presence of LW construction. Critical to notify IC
Info for e-CIDS can be obtained during _
BISP, Dept of Bldg (Structural Integrity Report), while responding, operating, & returning to qtrs, or any other outside activity
General Construction features of LW PD
1-3 stories in height w/flat or peaked roof. Built over crawl space & cellar constructed of 8” cement block. Attached & Semi-attached separated by fire wall that may extend through attic/cockloft
Heavier type of exterior finishing products (stone or brick veneer) may be enclosed to structure w/metal straps or wire mesh. They may fail _
As one complete unit when exposed to fire & high heat
Define Trussloft
Enclosed area between floors & ceilings where open truss construction is found
What is a danger of floor coverings using cement board, LW concrete, nylon pile carpet and tile
Retains heat under floor making it difficult to detect hot spots on floor above fire. Also gives false impression of support
Most common type of peaked roof found in LW construction
Open Web LW Wood Truss. Rafter (top chord of truss), roof decking, & ceiling joist (bottom chord of truss) can collapse as one complete unit into the structure
NYC Bldg Code requires LW constructed spaces between ceiling & floor above or ceiling & roof above be divided into approximately _
equal areas of 500 sq ft or less unless bldg equipped w/automatic sprinkler system
4 Most common types of LW systems in PD’s
LW parallel chord truss, Laminated Wood I-beams, Metal C-joists, & Composite Truss
LW Parallel Chord Wood Truss: Support system of 2X3” or 2X4” wooden web & chord members connected w/sheet metal gusset plates (gang nails) that only penetrate _
1/4-1/2” into wooden truss members. Weakest point of the systems
Another type of open-web joist uses finger points & glue to connect web & chords. The finger joists are approx _
3/4” deep w/No metal gusset plate. Fail rapidly with fire & high heat
Laminated Wood I-Beams- comprised of 1/2” Oriented Strand Board (OSB) or 3/8”-1/2” plywood web members, and 2X3” or 2x4” wood flanges. They may span lengths of _
Over 60’. Usually connected to load bearing walls w/sheet metal joist hangers
Wood I-Beams strength can be compromised by what pre-engineered features
Openings in web to accommodate utilities. Fire retardant spray on beam will dry out the wood over time making it brittle, further reducing its strength
Heavy fire & smoke condition on a floor or in cellar accompanied by little or no smoke condition on the floor or floors above may be an indication of
Concrete or gypsum floor poured over corrugated steel (Q-Decking) supported by C-Joists. The additional dead load may lead to early floor collapse
Composite truss is similar in design to _, but is comprised of 2 types of materials _
LW Parallel Wood Truss;
Wood & Steel. Commercially known as “Space Joist”
Once fire enters concealed space in PD w/LW construction, can members operate in fire area or area above fire
NOT until IC determines the risk of a planned coordinated interior attack. Especially true w/Open Web LW parallel chord & wood composite trusses