Ch. 12 Ops Ltwght Bldgs Flashcards Preview

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Flashcards in Ch. 12 Ops Ltwght Bldgs Deck (32):
1

______ are the deadliest style of roof construction per incident (Ch. 12 Ops in Ltwght Bldgs)

Wooden bowstring truss roofs

2

Collapse zones at end walls that have rafters resting on a truss and bearing wall should be at least ______ times the height of the wall.

2 1/2

3

Flat timber truss is variation of:

Bowstring truss

4

Flat timber truss more dangerous than bowstring in one way:

No visual hint; preplanning is critical

5

Bowstring and flat roof typically found in ____ and ____; there is ________ _________ of a civilian life hazard in these occupancies.

Industrial and storage
Little likelihood

6

Styles of lightweight trusses (3)

1) short scraps of 2x4s joined by gusset/gang nail plate (MOST COMMON)
2) 2x4 or even 2x3 top and bottom chords connected by tubular steel webs
3) very thin pieces of sheet metal stamped into gusset plates on the ends, acting as web members of truss

7

Lightweight trusses biggest drawback is:

Lack of mass

8

______ by far the most easily recognized type of lightweight construction in use.

Bowstring

9

Several flaws for trusses from FF standpoint

1) lack of mass compared to standard beam
2) connectors (conduct heat and/or fail)

10

Of all those types of buildings that firefighters may have to OPERATE in, those built with ______________ are the most dangerous.

Any of the lightweight construction methods

10

Two problems exist that make such operations dangerous in today's buildings:

New lightweight construction
Renovations

11

Older buildings
This type of roof or floor has several drawbacks from an ARCHITECTS point of view: (2)

Area that can be spanned (about 25 ft)
They are expensive

12

Danger of truss exists _______.

Only in fire conditions

13

Greatest danger to firefighters is: a truss depends on _______________.

Every one of its pieces AND the connections to hold it together.

14

Of all the modern styles, ____________ are the deadliest style of roof construction PER INCIDENT. If heavy fire is present, ___________.

Wooden bowstring truss roofs

All personnel must be removed from roof and from interior operations IN THE VICINITY of the truss roof.

15

Size of boards, bowstring truss vs flat timber truss

BS-2x10 with spaces between alternate boards, 20 ft spacing
FT-2x8 or 2x10 (chords), 2x4 or 2x6 web members, 20 ft spacing

16

Gusset plate penetrates wood

About 1/4 in.

17

Pin drilled into steel tube and wood chord has two effects

Drilling hole weakens 2x4
Steel pin and hole allow fire to attack from both inside and outside chord

18

A concern common to all PARALLEL-chord 2x4 trusses is ______________.

Risk of penetrating the top chord with a POWER saw blade during ventilation or overhaul (only covered with 1 in. of roofing and plywood)

19

While not a truss, poses many of the same problems
Top/bottom chord of 1 1/2 x 2 in. plywood with a web of 3/8 in. plywood

Plywood I-beam (parallel-chord beam)

20

Open web steel bar joists supporting corrugated metal deck
Bending steel bar in a repeating Z pattern
Up to 60 ft long and spaced 6 ft apart
ANOTHER style steel I-beam shapes with large hexagons cut out of the web

Metal deck roofs

21

MAIN drawback of open web steel bar joists and steel I beam shapes with hexagons cut out of webs is:

Lack of fireproofing and the way unprotected steel behaves when exposed to temperatures of a structural fire (collapse after few minutes)

22

Roof decking of metal deck roofs

1/16 in. thick, 3 ft wide and 20 ft long
Layer of tar
Insulating material, fiberglass or rubber, 3 in. thick

23

PRIMARY hazard to roof FFs with metal deck roofs is

Danger of falling into ventilation hole while cutting

24

Steel truss roofs when failing

Sag rather than snap
Fail in less than 5 minutes with heavy fire BUT don't fail without warning
Ample warning to FF's on top (below may not be able to see)

25

Fire in metal deck roof bldg/store

Use reach of large hose stream to cool unprotected joists
Start 3 stores over from fire store
Vent exposed store and stop fire advance

26

Three problems with metal deck

Falling in vent hole
Sudden catastrophic collapse
Metal deck roof fire

27

In metal deck roof fire, first step is to:

Cut through insulation and expose burning tar
2 x 2 ft section to determine which direction CORRUGATION runs
The long 2 ft strips perpendicular to the corrugations
2 1/2 in. stream

28

Renovated building
The great danger is that FF's will look at the building and ________________.

Take it at face value, utilizing tactics appropriate for original building

29

If roof ventilation isn't possible then:

Aggressive interior operations must ALSO CEASE

30

Lightweight roofs and floors
Life hazard with and without heavy fire attacking structural elements

Without heavy fire-offensive operations justified
With heavy fire-safest, most direct route. May involve exterior hose/approach (VES)
*key element is potential for saving lives. Still savable?"

31

Opening up sidewalls and directing stream into truss loft __________. On larger bldgs, roof ops are too dangerous so horizontal ventilation. What to do?

From platform basket may suffice (Elevating platforms devices of choice)