Chap 8 Timber Truss Roof Flashcards
Timber is
Wood construction larger than 2x4 but not large enough to be classified heavy timber or mill construction
3 ways FFs can die when operating at fires involving timber truss
- Ff can be killed operating outside a burning timber truss roof when the trusses collapse and push out masonry wall , the falling roof causes a 2nd collapse of wall
- Ff operating on the roof above burning timber truss roof
- Ffs operating inside a burning building can be crushed and burned when collapsing truss roof falls on them
Truss is a
Composition of large wooden members joined together in a group of triangles and arranged in a single plane so that loads applies at intersecting members will only cause direct stress( compression and tension)
The timbers in truss are joined together by bolts which pass through the center of metal connectors . The most common connector is ?
Split ring metal connector which is. Embedded in a prepared depression on the face of the timber
What is the purpose of the split ring metal connector in timber truss
To relieve the bolts that connect the trusses of shearing stress
How many bearing walls does a timber truss roof have ?
4 bearing walls
End of truss sections attach to side walls
Front and rear walls support the sloping hip rafters or roof joists extend directly from from front and rear truss sections
Why don’t rear walls in timber truss construction collapse as much as the front walls do?
Rear walls are more stable because of they have less openings than the front walls
Openings in a wall reduce load bearing capabilities and permit fire spread
What is the key to safe op at a timber truss fire
Early identification of a truss
3 size up indicators for truss roof in building
- Large open space without columns indicates a long span roof support such as a truss
- For bowstring trusses only - the mounded roof
3: certain occupancies frequently use truss construction in the roof ie. supermarkets bowling alleys , places of worship
Apse is
Part of the church that is semi- circle or u-shaped wall
Chancel
A space reserved for clergy includes the altar and front choir
Nave
Main seating area of the church
Rose window
Large round window at the front of a gothic church
Triforium
Middle story of the church (side balconies )
Dome
Hemispherical roof on a circle tower or base
Gothic
12 th century architecture , features pointed arch
Shapes of timber truss roof
Inclined plane truss (gable shape roof ) Parallel cord ( flat roof ) Bowstring truss (arch roof ) most common
What part of places of worship are the most unstable ?
The tower and the steeple
Chimneys next
Then free standing parapet walls
Church fires
The first arriving officer should locate and size up fire
He should determine if blaze can be extinguished by a hoseline
If can extinguish, first line is taken through front or side door to attack the seat of the fire to extinguish
Stretch largest hose
2nd large diameter hose should be stretched immediately to back up first line
As soon as flames are knocked down the walls and attic should be checked of concealed fire spread
If 2 hose lines do not extinguish fire withdraw ff and fight fire from outside
Which exposures are the most dangerous at places of worship ?
1- because of steeple
2 and 4 because of bearing walls
According to Dunn the priorities of FF in places of worship are
1 life hazard
2 incident stabilization
3. Property protection
Order of unstable parts of a place of worship
Tower with steeple, Tower with dome Chimneys Free standing walls Bearing walls
Primary venting of a place of worship should be where
At the rose window at front of church or temple
