ASTM D2899-95
(Practice)Standard Practice for Establishing Allowable Stresses for Round Timber Piles
Standard Practice for Establishing Allowable Stresses for Round Timber Piles
SCOPE
1.1 This practice contains procedures for establishing allowable stresses for round timber piles starting with clear wood strength properties.
1.2 Stresses established under this practice are applicable to piles conforming to the quality, straightness, spiral grain, knot, check, shake, and split provisions of Specification D 25.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 2899 – 95
Standard Practice for
Establishing Design Stresses for Round Timber Piles
This standard is issued under the fixed designation D 2899; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope average clear wood strength. Values of clear wood strength are
presented in Test Methods D 2555.
1.1 This practice covers basic principles for establishing
recommended design stress values for round timber piles.
5. Variability
1.2 This practice is intended for use by associations, tech-
5.1 There is a variation in the strength of clear wood within
nical societies, and other groups responsible for establishing
each species resulting from the normal differences in the
standards for design and use of round timber piles.
growth of individual trees. The variability of clear wood
1.3 Stresses derived by this practice are applicable to pile
strength properties is composed of variations between trees,
quality described in Specification D 25.
variations along the length of a tree, and variations between
1.4 This standard does not purport to address all of the
different locations within a cross section of a tree. Variability is
safety concerns, if any, associated with its use. It is the
presented in the form of standard deviations for clear wood
responsibility of the user of this standard to establish appro-
strength of small specimens in Test Methods D 2555.
priate safety and health practices and determine the applica-
5.2 The variation in pile strength is mostly due to differ-
bility of regulatory limitations prior to use.
ences between trees. Thus, the standard deviations for pile
2. Referenced Documents strength are less than for clear wood strength of small
specimens.
2.1 ASTM Standards:
D 25 Specification for Round Timber Piles
6. Density
D 2555 Test Methods for Establishing Clear-Wood Strength
6.1 The specific gravity of the solid wood substance of all
Values
clear wood is practically the same, regardless of species. Clear
3. Significance and Use wood is porous and its strength depends upon the amount of
wood substance present. Specific gravity provides an excellent
3.1 This practice is intended to establish design stresses
index of the wood substance a piece of dry wood contains, and
(working stresses or allowable stresses) for timber pile mate-
is therefore an index of its strength properties.
rial.
3.2 Safe and reliable design stresses are necessary in order
7. Decay
to achieve economical and dependable designs, fully utilizing
7.1 Ordinarily, the extent of decay in wood is difficult to
the physical properties of round timber piles. In using these
determine, and its effect on strength and shock resistance is
stresses, the engineer must also consider other factors, such as
greater than visual observation would indicate. Decay in piles
the location of the critical section, the soil bearing capacity, the
in any form is severely restricted or prohibited in accordance
ability of the pile to withstand driving stresses, and service
with Specification D 25.
conditions which may affect the design of the pile system.
3.3 Maximum economy is achieved when all piles are
8. Heartwood and Sapwood
stressed to the full allowable strength.
8.1 Heartwood and sapwood have been found to be of equal
strength and no requirement of heartwood need be made when
PRINCIPLES AFFECTING STRENGTH
PROPERTIES strength alone is the governing factor.
9. Moisture Content
4. Clear Wood Strength
4.1 The strength of timber piles is dependent upon the 9.1 When timber is seasoned, the direct effect of the loss of
moisture is the stiffening and strengthening of the wood fibers.
9.2 The effect of reduction of moisture content assumes
This practice is under the jurisdiction of ASTM Committee D-7 on Wood and
is the direct responsibility of Subcommittee D07.04 on Pole and Pile Products.
importance only when piles protrude above ground for some
Current edition approved Dec. 10, 1995. Published February 1996. Originally
distance, as in the case of piers and wharves or bridge
published as D 2899 – 70 T. Last previous edition D 2899 – 86.
construction. Piles are usually continuously wet for at least a
This revision includes changes only to the design stresses for oak piles calculated
major portion of their length.
from 14.1.1 and a change to 13.3 to make an exception for oak piles.
Annual Book of ASTM Standards, Vol 04.10.
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D 2899
10. Slope of Grain
where:
C|| 5 working stress in compression parallel to the grain
10.1 Slope of grain in a timber pile is a spiraling of the
for green untreated timber piles,
grain, and is measured by the twist in the direction of the fibers
S 5 average small clear crushing strength from Test
with respect to the axis of the pile. Specification D 25 limits
Methods D 2555, and
this characteristic so that its effect on strength is less than the
SD 5 standard deviation of small clear crushing strength
effect due to allowable knots.
from Test Methods D 2555.
11. Knots
15.1.1 For oak piles multiply the calculated compression
parallel to grain C|Ch, by the factor 1.1.
11.1 Knots reduce the strength of timber piles due to the
15.2 Calculate extreme fiber in bending as follows:
distortion of grain around the knot. Their effect on bending
strength is considerably greater than their effect on compres-
f 5 ~S 2 1.645 SD!/2.04 (2)
sion parallel to the grain. There is an increasing effect on
where:
strength with larger knots and closer grouping of knots.
f 5 working stress for extreme fiber in bending for green
Limitations on size and spacing of knots for piles are given in
untreated timber piles,
Specification D 25.
S 5 average small clear bending strength from Test
12. Duration of Load Methods D 2555, and
SD 5 standard deviation of small clear bending
...
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