ASTM D7381-07

Standard Practice for Establishing Allowable Stresses for Round Timbers for Piles from Tests of Full-Size Material

SIGNIFICANCE AND USE
This practice is primarily intended for use by associations, third-party grading agencies, technical societies and other groups that develop national design standards and use recommendations for round timber piles.
This practice provides procedures for establishing compression parallel to grain and bending stresses for round timber piles including: sampling of material for testing; methods of test and property calculation procedures; distribution analysis of test data; procedures for determining adjustments for critical section location; pile oversize, load sharing and treatment; and procedures for deriving allowable stresses.
In using allowable stresses established under this practice, factors specific to each end use which may affect the performance of the pile system shall be considered by the designer. Such factors include the location of the critical section, the bearing capacity of the soil, the ability of the pile to withstand driving forces, the properties of the cap or load distributive element tying piles together and the loading and conditions of service.
SCOPE
1.1 This practice contains procedures for establishing allowable compression parallel to grain and bending stresses for round timbers used for piling, based on results from full-size tests.Note 1
Allowable stresses for compression perpendicular to grain and shear properties are established in accordance with the provisions of Practice D 2899.
1.2 Stresses established under this practice are applicable to piles conforming to the size, quality, straightness, spiral grain, knot, shake and split provisions of Specification D 25.
1.3 A commentary on the practice is available from ASTM International.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.

General Information

• Status: Historical
• Publication Date: 31-Aug-2007
• ICS: 79.040 - Wood, sawlogs and sawn timber
• Technical Committee: D07 - Wood
• Drafting Committee: D07.04 - Pole and Pile Products

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7381 − 07
StandardPractice for
Establishing Allowable Stresses for Round Timbers for Piles
from Tests of Full-Size Material
This standard is issued under the fixed designation D7381; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D2555 PracticeforEstablishingClearWoodStrengthValues
D2899 Practice for Establishing Allowable Stresses for
1.1 Thispracticecontainsproceduresforestablishingallow-
Round Timber Piles
able compression parallel to grain and bending stresses for
D2915 Practice for Sampling and Data-Analysis for Struc-
round timbers used for piling, based on results from full-size
tural Wood and Wood-Based Products
tests.
D4761 Test Methods for Mechanical Properties of Lumber
NOTE1—Allowablestressesforcompressionperpendiculartograinand
and Wood-Base Structural Material
shear properties are established in accordance with the provisions of
Practice D2899.
D6555 Guide for Evaluating System Effects in Repetitive-
Member Wood Assemblies
1.2 Stresses established under this practice are applicable to
piles conforming to the size, quality, straightness, spiral grain,
3. Terminology
knot, shake and split provisions of Specification D25.
3.1 Definitions:
1.3 A commentary on the practice is available from ASTM
International. 3.1.1 allowable stress—the numeric value of pile strength
appropriate for use in design.
1.4 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1.2 end-bearing—compression parallel to grain stress
standard.
used in design when the pile load is not carried to the soil
through skin friction.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1.3 load sharing—the distribution of load that occurs in
responsibility of the user of this standard to establish appro-
two or more piles which are capped with a load-distributing
priate safety and health practices and determine the applica-
element that assures the piles deform as a group. The load
bility of regulatory limitations prior to use.
distributed to the piles in such a group is in proportion to the
stiffness of each pile. This distribution of loads to the piles in
2. Referenced Documents
the group reduces the effect of between pile variability and
2.1 ASTM Standards: increases system reliability over that of piles which perform as
single members.
D25 Specification for Round Timber Piles
D198 Test Methods of Static Tests of Lumber in Structural
3.1.4 skin friction—the interaction between the pile surface
Sizes
and the surrounding soil which serves to distribute load either
D245 Practice for Establishing Structural Grades and Re-
away from or into a pile. A positive skin friction refers to pile
lated Allowable Properties for Visually Graded Lumber
loads distributed to the soil. Negative skin friction refers to
D1036 Test Methods of Static Tests of Wood Poles
loads being distributed into the pile as a result of soil
D1990 Practice for Establishing Allowable Properties for
subsidence or consolidation.
Visually-Graded Dimension Lumber from In-Grade Tests
3.2 Symbols:
of Full-Size Specimens
c = circumference of a round timber pile
C = conditioning adjustment
cp
This practice is under the jurisdiction of ASTM Committee D07 on Wood and
C = adjustment for duration of load and miscellaneous
ds
is the direct responsibility of Subcommittee D07.04 on Pole and Pile Products.
factor of safety
Current edition approved Sept. 1, 2007. Published October 2007. DOI: 10.1520/
D7381-07. C = load sharing adjustment
ls
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
C ,C ,C ,C , = adjustments to F , F , E and EMOE
oc ob oe oeb c b
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
for pile oversizing relative to Specification D25 specified
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. minimum circumferences
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7381 − 07
C = adjustment of allowable compression parallel to grain 5. Sampling Full-Size Round Timbers
t
stress at pile tip to critical section location L
5.1 The population to be sampled shall be round timbers of
D = pile diameter
a particular species or species group meeting the provisions of
E = modulus of elasticity for individual member individual
i
Specification D25. Only those species groups that do not
compression parallel to grain specimen
exceed the variability, as measured by the criteria of Section 5
E = average modulus of elasticity of butt and tip compres-
a
ofPracticeD2555,ofthemajorlumberspeciesgroupssampled
sion parallel to grain specimens from the same pile
in the In-Grade lumber testing program in the United States
E’ = sample mean modulus of elasticity in compression
andCanadashallbeconsideredasasinglespeciesforsampling
E = allowable modulus of elasticity in compression
and analysis purposes. For species groups exceeding these
EMOE = effective modulus of elasticity in bending for an
i variability limits, the species composition should be changed
individual pile
such that the limits will be met by the remaining species in the
EMOE’ = sample mean effective modulus of elasticity in
group if sampling of the group as a single species is desired.
bending
NOTE 2—See X9.1 of Practice D1990 for discussion of in-grade
samplingofspeciesgroups.MajorspeciesgroupssampledintheIn-Grade
EMOE = allowable effective modulus of elasticity in bend-
lumber testing program are given in Note 3 of Practice D1990.
ing
F = allowable stress in bending
5.2 A representative sample (n) of all sizes (diameters) and
b
F = allowable stress in compression parallel to grain lengths of timber piles as in Tables X1.2 or X1.3 and
c
f = compression parallel to grain 5 % tolerance limit with Tables X1.4 or X1.5 of Specification D25 shall be selected for
cTL
75 % confidence determined from test results for the tip thespeciesorspeciesgroupbeingevaluated.Samplingbysize,
specimen length and class shall be in proportion to total production and
shall be distributed across plants representative of the produc-
f = bending 5 % tolerance limit with 75 % confidence
bTL
determined from test results ing region.
NOTE 3—Specification D25 pile specifications provide for only one
L = distance from pile tip to critical section, ft
grade and quality level.
L = distance from top of butt compression parallel to grain
e
test specimen to top of tip compression parallel to grain test 5.3 Individual piles selected as test material shall be green
specimen, ft and randomly chosen from inventory in the yard at each plant.
MORBP = modulus of rupture at breakpoint
5.4 Sample size shall be based on the principles of Practice
k = number of random variables used in random products
D2915 and shall be sufficient to provide reliable estimates of
simulation
the distributions of bending and compression parallel to grain
n = numberofpilesinaspeciesorspeciesgroupselectedfor
strengths of timbers of the species or species group being
testing
evaluated.Eachpileselectedfortestshallbeevaluatedforboth
p = exponent of L used to calculate pile length effect on
e bending and compression strength with compression speci-
compression strength
mens being cut from the butt and tip ends after the bending test
r = radius of gyration = D/4
is completed.
UCS = ultimate compressive strength
z = number of piles in a cluster
6. Test Methods and Calculation Procedures
6.1 All test members shall be maintained in a green condi-
4. Significance and Use
tion prior to test.
4.1 This practice is primarily intended for use by associa-
6.2 Each member shall be tested in bending in accordance
tions, third-party grading agencies, technical societies and
with the procedures of Test Methods D1036. Modulus of
other groups that develop national design standards and use
rupture at breakpoint (MORBP) and effective modulus of
recommendations for round timber piles.
elasticity in bending (EMOE) shall be calculated in accordance
4.2 This practice provides procedures for establishing com-
with the formulas given in 19.4 of Test Methods D1036.Ifan
pression parallel to grain and bending stresses for round timber
alternative formula is used to calculate EMOE, its derivation
piles including: sampling of material for testing; methods of
and assumptions shall be documented.
test and property calculation procedures; distribution analysis
NOTE 4—The cross-section of round timbers varies from butt to tip as
a result of taper. A linear taper between butt and tip is assumed in the
of test data; procedures for determining adjustments for critical
derivation of the EMOE equation. As tree tapers may not be linear but
section location; pile oversize, load sharing and treatment; and
parabolic, the moment of inertia of the resisting cross-section is underes-
procedures for deriving allowable stresses.
timated and the resulting bending EMOE value for the pile is typically
substantially higher than the average E based on compression parallel to
4.3 In using allowable stresses established under this prac-
grain tests.
tice, factors specific to each end use which may affect the
performance of the pile system shall be considered by the 6.3 After completion of the bending test, compression test
designer. Such factors include the location of the critical specimens shall be cut from the butt and tip ends of the
section, the bearing capacity of the soil, the ability of the pile member. These specimens shall be prepared and tested in
to withstand driving forces, the properties of the cap or load accordance with Sections 12–19 of Test Methods D198. The
distributive element tying piles together and the loading and same slenderness ratio, specimen length divided by the small
conditions of service. end radius of gyration (r), shall be used for the butt and tip
D7381 − 07
specimens but shall not exceed 17. Specific gravity disks shall 8.3 If a parametric distribution is to be used, the mean,
becutfromthebottomandtopofeachpile,immediatelyabove standard deviation and 5 % tolerance limit with 75 % confi-
the small end of the compression test specimens. dence (f or f ) determined for the property and sample
cTL bTL
using the methods of sections 3.4.3.2, 4.5, and Table 1 of
6.4 To prevent excessive end crushing, the compression
Practice D2915.
specimensshallbebandedortheendsair-driedpriortotesting.
Load-deformationdatashallbeobtainedforbothspecimens.In 8.4 If a nonparametric distribution is to be used, the sample
test values shall be arranged in ascending order and the mth
place of the testing speeds specified in section 17.3 of Test
Methods D198, a rate of straining (in./in. per min) such that order statistic selected as the sample 5 % tolerance limit with
75 % confidence (f or f ) in accordance with 4.5.4, 4.5.5,
maximum load is obtained between 1 and 5 min shall be used
cTL bTL
andbothbuttandtipspecimensshallbetestedatthesamerate. and Table 2 of Practice D2915.
NOTE 5—A range of 1 to 5 min in failure times is within the range of
9. Critical Section Located Above the Pile Tip
10 s to 10 min specified for in-grade testing of lumber in section 34.4 of
Test Methods D4761.
9.1 Paired butt and tip compression parallel to grain UCS
6.5 Ultimate compression strength (UCS) and modulus of
values shall be used to establish an equation for adjusting tip
elasticity (E) shall be calculated for both the butt and tip
compression allowable design values (F ) when the critical
i
c
specimens using the area of the small end of each specimen.
section is located above the tip as a result of skin friction.
Values of E shall be based on the linear portion of the
i
9.2 For each test pile, the difference between butt and tip
load-deformationcurveswithsuitableadjustmentmadeforany
UCS values shall be normalized using the following calcula-
nonlinearity occurring at the beginning of the test.The average
tion:
of the E values for the butt and tip specimens shall be
i
p
R 5 @~UCS 2 UCS !/UCS #/L (1)
calculated as the E of the pile. i butt tip tip e
a
where:
7. Reporting Requirements for Sampling and Testing
R = normalized individual pile length effect on compression
i
7.1 The following information shall be reported: strength p = 1.6.
7.1.1 The production volumes for the various sizes, lengths
9.3 If the significance of the slope coefficient of the regres-
and classes of piles building poles used to develop the
sion of R on L is not less than a probability of 25 %, the
i e
sampling plan for each species or species group evaluated.
average of the R values for the sample (R ) shall be used to
i avg
7.1.2 The methods used to select the manufacturing facili-
establish the following equation for determining C:
l
ties for sampling and the individual test piles from each
p
C 5 ~R 3100!/L (2)
l avg
facility.
7.1.3 A complete description of each test specimen includ- where:
ing length, butt and tip circumference, rings per inch, percent
C = percentage increase in pile compression strength at
l
summerwood, slope of spiral grain and the maximum indi-
distance L from the pile tip p = 1.6
vidual knot size and the maximum sum of knot diameters in
9.4 If the significance of the slope coefficient is less than
any one-foot of pile length.
25 %, the value of the exponent p shall be changed so as to
7.1.4 The diameters of the small and large ends of the butt
meet this criterion. Individual R values based on a butt
i
and tip compression parallel to grain test specimens selected
compression specimen containing a split that occurred during
from each pile and the maximum individual knot size and the
the bending test shall not be included in the regression analysis
maximum sum of knot diameters in any one-foot of length in
nor in the calculation of R for the sample.
avg
each of these specimens.
7.1.5 Slenderness ratios, rate of load application, time to
10. Effect of Pile Sizes Exceeding Specification D25 Size
maximum load, section properties, specific gravity, formulas
Class Minimums
used to calculate strength and stiffness properties and other
10.1 Piles are marketed in accordance with circumference
information as required by the provisions of Test Methods
(diameter) and length specified in Specification D25. The
D198 and D1036.
actual diameters of piles qualifying for a particular circumfer-
7.1.6 Acomplete description of the analytical methods used
ence class generally exceed the
...