Building Design and Construction Handbook - Merritt - Ventech!

TABLE 10.39 Stress Values for Treated Wood Poles*
Species
Modulus of
rupture,
extreme fiber
in bending,
psi†
WOOD CONSTRUCTION 10.81
tration of 3% in solution. To minimize end cutting and field treatment of footing
plates, these members may be extended past the corners of the foundation.
Only corrosion-resistant fasteners should be used in wood foundations.
To keep the interior of the foundation walls dry, it is necessary to enclose the
exterior with a waterproofing membrane, such as polyethylene film, and to ensure
good drainage. For the latter purpose, the ground surface should be sloped away
from the building at 1 ⁄2 in/ft for a distance of at least 6 ft and gravel should be
placed against the walls and under the cellar floor.
(See ‘‘Permanent Wood Foundation System—Technical Report 7’’ American
Forest & Paper Association; ‘‘Permanent Wood Foundations—Design and Construction
Guide,’’ Southern Forest Products Association, for additional information.)
10.27 POST FRAME AND POLE CONSTRUCTION
Wood poles and posts are used for various types of construction, including flagpoles,
utility poles, and framing for buildings. These employ preservatively treated
round poles or posts with square or rectangular cross sections that are set into the
ground as columns. The ground furnishes vertical and horizontal support and prevents
rotation at the base.
Post frame construction is used extensively in agricultural buildings and in many
commercial and industrial building applications.
In buildings with post frame and pole construction, a bracing system is often
provided at the top of the poles or posts to reduce bending moments at the base
and to distribute loads. Design of buildings supported by poles or posts without
bracing requires good knowledge of soil conditions, to eliminate excessive deflection
or sidesway. For allowable foundation and lateral pressures, see the applicable
building code.
Extreme
fiber in
bending
F b, psi‡
Modulus of
elasticity
E, psi‡
Compression
parallel to grain
F c, psi‡
Cedar, northern white 4000 1540 600,000 740
Cedar, western red 6000 1850 900,000 1030
Douglas fir 8000 2700 1,500,000 1360
Hemlock, western 7400 2380 1,300,000 1250
Larch, western 8400 2940 1,500,000 1500
Pine, jack 6600 2100 1,100,000 1100
Pine, lodgepole 6600 1820 1,100,000 980
Pine, ponderosa 6000 1710 1,000,000 920
Pine, red or Norway 6600 2100 1,300,000 1020
Pine, southern 8000 2740 1,500,000 1360
* Air-dried prior to treatment.
† Based on American National Standard Specifications and Dimensions for Wood Poles, ANSI 05.1-
1992.
‡ Based on ASTM D 2899-95, ‘‘Tentative Method for Establishing Design Stresses for Round Timber
Piles.’’