Dunn Flashcards
DUNN - WOOD FRAME BUILDING COLLAPSE
- Warning signs
A) 90 degree angle collapse (corner walls splitting apart)
B) Lean over - structure starts to lean or tilt to one side
C) Inward/outward - collapse may not exhibit any structural warning at
all. Sometimes the only indication that a collapse
is imminent is a serious fire burning for a long
period of time on the lower floor.
- Three most common types of construction
A) Braced frame
B) Balloon Frame
C) Platform and Lightweight Frame
- Lightweight wood construction - from a fire protection point of view it
is inferior construction. It is recommended that when a fire involves
truss construction such as a concealed space of the floor or
roof, the strategy should be:A) To remove occupantsB) Fight the fire defensively from the outside
DUNN - BRACED FRAME CONSTRUCTION
A) Braced frame construction presents the greatest firefighting danger
of the three types of wood construction.
B) A 3 story braced frame structure frequently collapses in an inward/
outward collapse. (Most dangerous wood frame collapse, may not
exhibit any warning signs)
C) Inward/outward collapse = top two walls fall inward, bottom floor
outward.
D) Braced frame is sometimes referred to as post & girt construction.
E) Vertical timbers are called post and horizontal timbers are called girts
F) These larger timbers known as the post and girt reinforce the entire
2x4” framework.
G) However these larger timbers are connected by a mortise and tenon
joint.
H) The ends of the horizontal timbers are cut down to fit into a mortise
opening. The mortise opening is cut into the vertical post.
I) The mortise and tenon joint is the weak link in this type of
construction.
DUNN - COLLAPSE OF BUILDINGS UNDER CONSTRUCTION
A) It takes TWENTY SEVEN (27) days for concrete to reach its
maximum strength.
B) After 48 hours, wood form work can be removed.
C) Most serious fire and most serious collapse in buildings under
construction occurs during a fire in the formwork.
D) Spalling is the collapse (failure) of the outer layers of concrete,
caused by the moisture in the concrete heating up and expanding.
E) 2 types of concrete spalling
Explosive - concrete is driven upward
Drop - concrete falls down on your head
F) Scaffolding Collapse - serious collapse during a fire. Supports large
amounts of building materials, sometimes may be supported by
metal framework or by cantilevered aluminum beams which extend
out beyond the structure several floors above.
G) Identifying the hoist car/construction elevator used by workers:
operating controls are inside the car / operator rides inside the car /
built in safety brake will stop the car in event of a free fall.
H) Burning embers - major cause of fire extension at framework fires,
combustible roofs of smaller nearby structures
and spread fire.
DUNN - PRIORITY OF FIRE GROUND STRATEGY “PCP”
“PCP”
P - Protection of life 1st
C - Containment of fire 2nd
P - Protection of property 3rd
DUNN - SLOPING PEAKED ROOFS
- Sloping Peaked Roofs “2-3-9”
A) Flat roof has 2 primary structural members (2 bearing walls)
B) Gable roof has 3 primary structural members (2 bearing walls and
one ridge rafter)
C) Hip Roof has 9 structural members (4 bearing walls, one ridge rafter,
and 4 hip rafters)
D) A bowstring truss roof has 4 bearing walls
E) The stability of a sloping truss roof deck depends on the number of
purlins running perpendicular to the trusses and on the truss
spacing.
F) Roof rotting on sloping roofs is often found at ROOF EDGES,
WHERE ROOFS CHANGE SLOPE AND WHERE A SLOPING ROOF
ABUTS A VERTICAL PLANE.
G) A low pitched roof, found in ranches, may be walked on, depending
upon the type of shingle and the weather conditions.
H) A medium pitched roof should have a roof ladder secured at the
ridge, or be butted by a parapet wall at the base to ensure footing for
walking or operating.
I) A high pitched roof, found on “A” frame dwellings and English Tudors,
cannot be walked on safely, even with a roof ladder. A FF must
operate from an extended Aerial Ladder or while standing in the
bucket of a TL.
J) Slate and tile roofs have the same dangerous effect as a tile or
terrazzo floor above a serious fire: they conceal the amount of heat,
smoke and flame below and then collapse in one large section
without any warning signs.
K) A roof ladder will protect FFs from roof deck collapse but WILL NOT
PROTECT FFs FROM A ROOF RAFTER COLLAPSE. Only standing
and operating from an Aerial Ladder or Aerial Platform can protect a
FF from a rafter collapse.
L) When FFs are operating at a private home with a sloping roof, it is
more effective to remove smoke from the structure by venting top
floor windows than by cutting a vent hole.
M) FD operations for sloping roofs should be based in the following
priority order: 1. Life Safety
2. Fire Containment
3. Property Protection
N) Because a sloping roof sheds water and snow when properly
pitched, it may be designed to support LESS of a live load than a flat
roof.
DUNN - TIMBER TRUSS ROOFS
- Timber Truss Roofs
A) Truss roof construction is the most dangerous roof system that a FF
will encounter.
B) In a timber truss building, the main fire will be in the roof structure,
not in the content below.
C) A truss roof concealed by a ceiling is much more dangerous to FFs
than a truss roof without a ceiling.
- Firefighting Strategies for Timber Trusses Concealed by Ceiling
A) When fire extends to a timber truss attic space, prepare for a
defensive outside attack and protect exposures. Order all FFs above
and below the burning timber truss attic space out of the building.
- Firefighting Strategy for Timber Trusses Not Concealed by Ceiling
A) The first arriving engine company at a timber truss roof building
without a ceiling should be to attack the fire directly with a large
diameter hoseline. A powerful water stream, capable of reaching a
distance of 50 feet will be needed. This first hoseline should attack
the main body of fire. If the first hose stream does not control the
flames WITHIN THE FIRST FEW SECONDS OF EATER DISCHARGE,
and it appears the fire will increase, interior firefighting should be
discontinued and FFs withdrawn.
B) The fire must show IMMEDIATE SIGNS of extinguishment by the first
hose stream, or an outside attack should be ordered.
C) If the first hoseline is successful and controls the fire at floor level
OR IN A SINGLE TIMBER TRUSS, and it appears that the fire will not
spread, a backup, large diameter hoseline should be stretched int
the building and sweep the underside of the roof if necessary.
- Bowstring Truss Roofs
A) Often when Bowstring Truss a Roofs fail, one or more exterior walls
collapse. The front wall collapses more frequently than the rear wall.
B) When roof stability is assured and roof venting is needed, FFs can
sometimes open the skylights or scuttle covers and leave the roof
immediately. NOTE: THIS IS NOT ALLOWED AS PER FFP
TAXPAYERS (This is only in Dunn / FFP Taxpayers PROHIBITS
operating on a Bowstring Roof when there is a fire in that building)
C) In Bowstring Truss Roofed building which does not have the web
members enclosed with plasterboard, vent openings may be made
in the front and rear sloping portions of the roof to provide cross
ventilation of the entire roof space.
D) To quickly determine if a fire has spread to the roof space of a
bowstring truss, a TRIANGULAR cut may be made in the sloping
front or rear of the roof from the safety of an aerial platform.
E) When evacuating a failing Bowstring truss roof, a member should
evacuate in a direction perpendicular to the failing truss.
F) FFs attempting the initial hoseline attack on a fire should be
positioned behind a TRUSS section NEXT TO THE ONE ON FIRE.
DUNN - PLACES OF WORSHIP
- Collapse Dangers in Places of Worship (from least to most stable)
A) Tower and Steeple B) Tower and Dome C) Chimneys D) Freestanding Parapet Walls E) Non Bearing Walls F) Bearing Walls (roof and floor collapse with the bearing wall collapse)
- Places of Worship Tactics
A) If an interior attack is to be attempted at a church fire, the first
engine shall stretch the largest diameter hose available through a
front or side door and attack the seat of the fire.
B) A second hoseline must be taken in the place of worship to backup
the first line.
C) If 2 lines do not extinguish the fire, withdraw members and fight fire
from outside.
D) The first Aerial ladder (TL) should be positioned in a CORNER SAFE
AREA and the aerial platform should be supplied with a large
diameter hose and raised to the ROSE WINDOW. The ENTIRE rose
window should be vented.
E) If the fire is extinguished by interior hoselines, the side stained glass
window MAY NOT have to be vented. However, if the interior must
be vented for the advance of the first 2 lines, then the stained glass
windows nearest to the fire on both sides of the building should be
vented first.
F) A burning church or temple may have the interior fire spread
problems of ordinary construction, but the exterior fire spread
problems are similar to heavy timber mill buildings.
DUNN - STEEL
- General
A) Heated steel expands, bends, twists, sags and buckles when heated
by fire.
B) Shaped steel INCREASES strength, greater load bearing capacity,
less material.
C) Examples 1. Steel bar joist truss
2. Steel C-beams
D) Thinner steel reaches the critical temperatures much faster than
thick solid steel.
E) Large solid steel can absorb more heat before reaching the critical
temperature.
- Steel Open Web Bar Joists
A) Unprotected steel bar joist may collapse after 5-10 minutes of fire
exposure.
B) Serious fire in an unoccupied building, with a roof supported by unprotected lightweight steel bar joists or C-beams, If the stability of the roof is in question:
- Too dangerous to send FFs on roof for ventilation & for interior
hoseline attack.
- Consider a strategy of horizontal ventilation and defensive exterior
attack.
- Temperature of the Fire
A) 1100 degrees F - failure temperature of steel in the fire service
B) At 1100 degrees F steel will lose almost half (40%) of its load
carrying capacity.
C) The temperature within the steel itself - must be raised to 1100
degrees F.
- Load Stress - the load supported by a structural member
A) The greater the supported load, the faster the structural member can
fail.
B) The heavier the supported roof deck, the faster the collapse of
heated steel roof beams.
- Thickness of the steel
A) A heavy, thick section of steel has more resistance to fire than a
lightweight section.
B) There is little heat sink capacity in thin lightweight steel structural
components.
- Fire Size
A) If a small fire comes into contact with a large steel beam, the steel
will absorb heat and transfer it away to cooler parts of the structure
element.
B) A large fire area, where flames involve much of the steel beam in a
shorter period of time, will heat the steel beam to its critical
temperature more quickly.
C) UNPROTECTED steel bar joists and C-beams are not fire resistive
and can collapse after 5-10 minutes of fire exposure.
DUNN CHAPTER 12
1) Suspended ceilings are most often found in:
A) Stores (to cover old, out of fashion ceilings)
B) Top floors of MDs (insulates the building)
C) Renovated buildings (every floor of every apartment to conserve
energy for heating and cooling)
2) 3 Types of suspended ceilings:
A) A wood grid system with permanently affixed ceilings
B) A metal grid system with permanently affixed ceilings
C) A lightweight metal grid system with removable ceiling panels
D) The ceiling collapse killing NYC firefighters is the WOOD GRID
SUSPENDED SYSTEM.
E) Most important 1st step to rescue members trapped under a
collapsed ceiling is to sweep the area above the ceiling with a
hoseline.
DUNN CHAPTER 13
1) Basic Stair Types
A) Straight run (will collapse of the floor collapses)
B) U-Return (will NOT collapse if the floor collapses)
C) L-Shaped (found in private dwellings)
D) The U-Return is the preferred stair in modern building construction
because it reduces the amount of floor area needed, adding valuable
floor space.
E) Most FREQUENT cause of collapse in U-Return stairs is failure of a
stone stair tread or step.
F) Most SERIOUS injuries to members on these stairs occur when
intermediate stair landing collapses.
DUNN CHAPTER 14
1) Exterior Screened Fire Escape
A) Extend from the ground to the TOP FLOOR (no gooseneck or drop
ladder)
B) The SAFEST type of fire escape.
C) Wide enough for 2 people to descend side by side
2) Party Balcony Fire Escape
A) The hazard is collapse from overloading or failure of the supports
B) Safest way to remove people is through the adjoining apartment
3) Standard Fire Escape
A) Most common type of fire escape found
B) Most frequent cause of injury to members is caused by step
collapse.
C) Stand under the fire escape when lowering the drop ladder.
4) Counterbalanced Stairway
A) Use FDNY ground ladders to remove people found on these fire
escapes.
B) The impact of the stairway striking the ground can cause the entire
metal stairway to collapse.
DUNN - MASONRY WALL COLLAPSE
1) 90 Degree Angle Collapse
A) Most common type of masonry wall collapse B) Walls fall straight out from the top C) Strikes ground at a distance equal to top of wall
2) Curtain Fall Collapse
A) Wall falls like a curtain cut loose at the top
B) Wall will fall straight down with brick and mortar forming a pile at
base of wall.
3) Inward / Outward Collapse
A) Upper section of wall falls inward, lower section kicks outward
B) Upper section may also lean initially inward and slide outward to
street, bottom first.
