Chapter 10- Noncombustible Construction Flashcards
What, then is the difference between noncombustible and fire resistive construction? The answer is simple–the level of fire resistance (fire rating) assigned to the structural __, __, __, and __.
Frame
Walls
Floors
Roof
Many noncombustible buildings are __-__ stories in height, with the maximum height being __ stories for certain types of occupancies. Fire resistive construction, by comparison, is permitted to be of unlimited height.
1-3
12
Although the use of concrete is found in some buildings of noncombustible construction, noncombustible construction relies heavily on the use of __ for its structural system, including the roof and floor framing.
Steel
The use of __ in Type 2 construction is typically limited to __ walls and __ enclosures.
Concrete
Exterior
Shaft
Steel is tremendously strong. Its Modulus of elasticity (a measure of its ability to distort and restore) is about __ million pounds per square inch–far more than any other material.
29
Steel’s compressive strength is equal to its tensile strength. Its __ strength is about __ of its tensile strength.
Shear
3/4
The heat evolved by a fire can be triaged–that is, considered and treated according to priority needs. In reverse priority, this heat can be classified as follows:
- Heat leaving the structure
- Heat being evolved from contents that are burning
- Heat being absorbed by contents or structural elements that will be ignited or caused to fail
The following abbreviations are used for different shaped steel members:
C: channels CB: castellated beams L: angles S: America Standard (I beam) W: wide flange beams and columns WT: structural tees
__ frames are a cousin to the arch and are used to achieve wide clear spans.
Rigid
In the rigid frame, the column is __ at the base and tapers to its __ point at the top where it meets the roof rafter.
Narrow
Widest
This rafter is also tapered so that it is narrow at the __ and wide where it joins the __.
Ridge
Column
Rigid frames can provide clear spans of about __ feet.
100
The better the building is tied together to resist __ load, the more likely it is to suffer __ collapse due to fire distortion.
Wind
Progressive
__ wall panels can be used on any framed building and, in fact, are used on many concrete buildings.
Metal
The use of lightweight galvanized steel studs for exterior walls has surged. Shaped like the letter __, these studs are held in place with __ shaped tracks on top and bottom.
C
U
Steel will expand __ to __ percent in length for each 100 degrees F rise in temperature.
0.06 to 0.07
Recent tests conducted by the National Institute of Standards and Technology (NIST) of a typical basement room fire reached 1500 degrees F in __ minutes, reflecting the presence of today’s heavy plastic fire loads rather than any special significance of basements.
5
In a fire equivalent to the standard test fire, the bar joists generally will fail in about __ minutes.
7
A number of options are open to the designer to deal with these characteristics of steel as they relate to fire risk:
- Ignore the problem
- Rely on inadequate code enforcement
- Take a calculated risk
- Protect (insulate) the steel
- Protect the steel with sprinklers
- Protect the steel with an internal water cooling system
- Locate the steel out of range of the fire
__ and __ on highways provide a good example of unprotected steel that is vulnerable to an occasional gasoline or oil truck fire.
Bridges
Overpasses
In some building codes, steel used to support roofs at a certain distance above the floor (usually about __-__ feet) does not require protection. Atria roofs over __ feet are given this exemption as well.
20-30
55
The lack of fire protection for unprotected steel may reflect a calculated risk taken by the building’s developers and managers. For our purposes, there are three classes of calculated risks:
Financial or economic
Engineering
Forget it
In recent years, the __ roof (composed of ethylene propylene diene monomer (EPDM)) has increased in popularity in Type 2 construction.
Rubber
Another relatively new type of roof is the __ __ (mod bit) roof. In this construction technique, a traditional built up roof is modified by the addition of synthetic polymers to reinforce the roof.
Modified bitumen
