Building Design and Construction Handbook - Merritt - Ventech!

WOOD CONSTRUCTION 10.83
TABLE 10.41 Safe Concentric Column Loads on Douglas-Fir and
Southern-Pine Poles, lb*
Top diam, in 8 7 6 5
Pole class
Unsupported pole length,
ft (above ground line):
2 3 5 6
0 68,500 52,500 38,500 26,000
10 68,500 51,000 28,500 14,000
12 61,500 36,500 20,500 10,000
14 46,000 27,500 15,500 8,000
16 36,000 22,000 12,500 6,500
18 29,500 17,500 10,000 5,000
20 24,500 15,000 8,500 4,500
25 16,500 10,000 6,000
30 12,500 7,500
35 10,000 6,000
* See the latest edition of Standard Specifications and Dimensions for Wood
Poles, ANSI 05.1.
(See also ‘‘Design Properties of Round, Sawn and Laminated Preservatively
Treated Construction Poles and Posts,’’ ASAE Engineering Practice, EP 388.2 for
additional information.)
10.28 DESIGN FOR FIRE SAFETY
For buildings with structural lumber or timber framing, fire protection of the occupants
and of the property itself can be enhanced by taking advantage of the fireendurance
properties of wood in large cross sections and selecting details that make
buildings fire-safe. Building materials or features alone or detection and fireextinguishing
equipment alone cannot provide maximum safety from fire in buildings.
A proper combination of these measures, however, will provide the necessary
fire protection (Art. 3.5).
When exposed to fire, wood forms a self-insulating surface layer of char, which
provides fire protection. Even though the surface chars, the undamaged wood beneath
retains most of its strength and will support loads in accordance with the
capacity of the uncharred section. Heavy-timber members have often retained their
structural integrity through long periods of fire exposure and remained serviceable
after refinishing the charred surfaces. This fire endurance and excellent performance
of heavy timber are attributable to the size of the wood members, and to the slow
rate at which the charring penetrates.
The structural framing of a building, which is the criterion for classifying a
building as combustible or noncombustible, has little to do with the hazard from
fire to the building occupants. Most fires start in the building furnishings or contents
and create conditions that render the inside of the structure uninhabitable long
before the structural framing becomes involved in a fire. Thus, whether the building
is of a combustible or noncombustible classification has little bearing on the potential
hazard to the occupants. However, once the fire starts in the contents, the
material of which the building is constructed can be of significant help in facilitating