Ch. 12 Ops Ltwght Bldgs

Question 1

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

Answer 1

Wooden bowstring truss roofs

Question 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.

Answer 2

2 1/2

Question 3

Flat timber truss is variation of:

Answer 3

Bowstring truss

Question 4

Flat timber truss more dangerous than bowstring in one way:

Answer 4

No visual hint; preplanning is critical

Question 5

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

Answer 5

Industrial and storage

Little likelihood

Question 6

Styles of lightweight trusses (3)

Answer 6

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

Question 7

Lightweight trusses biggest drawback is:

Answer 7

Lack of mass

Question 8

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

Answer 8

Bowstring

Question 9

Several flaws for trusses from FF standpoint

Answer 9

1) lack of mass compared to standard beam

2) connectors (conduct heat and/or fail)

Question 10

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

Answer 10

Any of the lightweight construction methods

Question 10

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

Answer 10

New lightweight construction

Renovations

Question 11

Older buildings

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

Answer 11

Area that can be spanned (about 25 ft)

They are expensive

Question 12

Danger of truss exists _______.

Answer 12

Only in fire conditions

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Wooden bowstring truss roofs

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

Question 15

Size of boards, bowstring truss vs flat timber truss

Answer 15

BS-2x10 with spaces between alternate boards, 20 ft spacing

FT-2x8 or 2x10 (chords), 2x4 or 2x6 web members, 20 ft spacing

Question 16

Gusset plate penetrates wood

Answer 16

About 1/4 in.

Question 17

Pin drilled into steel tube and wood chord has two effects

Answer 17

Drilling hole weakens 2x4

Steel pin and hole allow fire to attack from both inside and outside chord

Question 18

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

Answer 18

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

Question 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

Answer 19

Plywood I-beam (parallel-chord beam)

Question 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

Answer 20

Metal deck roofs

Question 21

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

Answer 21

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

Question 22

Roof decking of metal deck roofs

Answer 22

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

Question 23

PRIMARY hazard to roof FFs with metal deck roofs is

Answer 23

Danger of falling into ventilation hole while cutting

Question 24

Steel truss roofs when failing

Answer 24

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)

Question 25

Fire in metal deck roof bldg/store

Answer 25

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

Question 26

Three problems with metal deck

Answer 26

Falling in vent hole
Sudden catastrophic collapse
Metal deck roof fire

Question 27

In metal deck roof fire, first step is to:

Answer 27

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

Question 28

Renovated building

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

Answer 28

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

Question 29

If roof ventilation isn’t possible then:

Answer 29

Aggressive interior operations must ALSO CEASE

Question 30

Lightweight roofs and floors

Life hazard with and without heavy fire attacking structural elements

Answer 30

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?”

Question 31

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

Answer 31

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