ASTM D2555-17a(2024)e1

Standard Practice for Establishing Clear Wood Strength Values

ABSTRACT
This practice presents the two standard methods for determining the strength values of clear wood of different species in the unseasoned condition, unadjusted for end use, applicable to the establishment of working stresses for different solid wood products such as lumber, laminated wood, plywood, and round timbers. Method A provides for the use of the results of surveys of wood density involving extensive sampling of forest trees, in combination with the data obtained from standard strength tests. The average strength properties are obtained from wood density survey data through linear regression equations establishing the relation of specific gravity to the several strength properties. Method B, on the other hand, provides for the establishment of tables of strength values based on standard tests of small clear specimens in the unseasoned condition for use when data from density surveys are not available. Separate tables are employed to present the data on woods grown in the United States and on woods grown in Canada. Guidelines for the interpretation of the data in terms of assigned values, information basic to the translation of the clear wood values into working stresses, presently available data with appropriate provisions for their application and use, and methods for estimating some useful mechanical properties by relating them to other properties are presented herein as well.
SCOPE
1.1 This practice covers the determination of strength values for clear wood of different species in the unseasoned condition, unadjusted for end use, applicable to the establishment of design values for different solid wood products such as lumber, laminated wood, plywood, and round timbers. Presented are:  
1.1.1 Procedures by which test values obtained on small clear specimens may be combined with density data from extensive forest surveys to make them more representative,  
1.1.2 Guidelines for the interpretation of the data in terms of assigned values for combinations of species or regional divisions within a species to meet special marketing needs, and  
1.1.3 Information basic to the translation of the clear wood values into design values for different solid wood products for different end uses.  
1.1.4 For species where density survey data are not as yet available for the re-evaluation of average strength properties, the presently available data from tests made under the sampling methods and procedures of Test Methods D143 or Practice E105 are provided with appropriate provision for their application and use. Because of the comprehensive manner in which the density survey is undertaken, it follows that the re-evaluated strength data are intended to be representative of the forest stand, or rather large forest subdivisions.  
1.1.5 Some useful mechanical properties (tensile strengths parallel and perpendicular to grain, modulus of rigidity for a longitudinal-transverse plane, and transverse modulus of elasticity) have not been extensively evaluated. Methods are described for estimating these properties by their relation to other properties.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2024
• ICS: 79.040 - Wood, sawlogs and sawn timber
• Technical Committee: D07 - Wood
• Drafting Committee: D07.02 - Lumber and Engineered Wood Products

Relations

• Replaces: ASTM D2555-17a(2024) - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Feb-2024
• Referred By: ASTM D5574-94(2021) - Standard Test Methods for Establishing Allowable Mechanical Properties of Wood-Bonding Adhesives for Design of Structural Joints
• Effective Date: 01-Feb-2024
• Referred By: ASTM D2899-12(2017) - Standard Practice for Establishing Allowable Stresses for Round Timber Piles
• Effective Date: 01-Feb-2024
• Referred By: ASTM D5536-17(2023) - Standard Practice for Sampling Forest Trees for Determination of Clear Wood Properties
• Effective Date: 01-Feb-2024
• Referred By: ASTM D9-20 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 01-Feb-2024
• Referred By: ASTM D25-12(2022) - Standard Specification for Round Timber Piles
• Effective Date: 01-Feb-2024
• Referred By: ASTM D3957-09(2020) - Standard Practices for Establishing Stress Grades for Structural Members Used in Log Buildings
• Effective Date: 01-Feb-2024
• Referred By: ASTM D1990-19 - Standard Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens
• Effective Date: 01-Feb-2024
• Referred By: ASTM D2395-17(2022) - Standard Test Methods for Density and Specific Gravity (Relative Density) of Wood and Wood-Based Materials
• Effective Date: 01-Feb-2024
• Referred By: ASTM D245-22 - Standard Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber
• Effective Date: 01-Feb-2024
• Referred By: ASTM D3737-18(2023)e1 - Standard Practice for Establishing Allowable Properties for Structural Glued Laminated Timber (Glulam)
• Effective Date: 01-Feb-2024
• Referred By: ASTM D2559-12a(2018) - Standard Specification for Adhesives for Bonded Structural Wood Products for Use Under Exterior Exposure Conditions
• Effective Date: 01-Feb-2024
• Referred By: ASTM D2915-17(2022) - Standard Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
• Effective Date: 01-Feb-2024
• Referred By: ASTM D5751-99(2019) - Standard Specification for Adhesives Used for Laminate Joints in Nonstructural Lumber Products
• Effective Date: 01-Feb-2024
• Referred By: ASTM D6570-18a(2023)e1 - Standard Practice for Assigning Allowable Properties for Mechanically Graded Lumber
• Effective Date: 01-Feb-2024

Overview

ASTM D2555-17a(2024)e1 - Standard Practice for Establishing Clear Wood Strength Values provides standardized methods for determining the strength properties of clear, unseasoned wood across different species. This practice is widely used in the development of working stresses and design values for a variety of solid wood products such as lumber, laminated wood, plywood, and round timbers. The standard, published by ASTM International, ensures wood strength values are determined using consistent methodologies, supporting both regulatory compliance and safe engineered wood product design.

Key Topics

• Methods for Strength Value Determination:
  ASTM D2555 outlines two primary methods for establishing clear wood strength properties:

  • Method A: Combines results from extensive wood density surveys with data from standard strength tests. This involves:
    • Sampling forest trees to collect specific gravity data
    • Using regression analysis to relate wood density to mechanical properties
    • Applying findings over unit areas and regional divisions
  • Method B: Compiles strength value tables from standard tests on small clear specimens when density surveys are not available. Separate tables present data for woods from the United States and Canada.

• Translation to Working Stresses:
  The practice includes guidelines for interpreting clear wood values and converting them into design values suitable for engineering applications and various end uses.

• Handling of Combinations and Regional Variability:
  Procedures are provided for:

  • Assigning strength values to species groupings for marketing or special regional requirements
  • Weighting values based on standing timber volume
  • Adjusting for group variability to ensure safety

• Estimation of Mechanical Properties:
  Methods are described for estimating additional mechanical properties, such as tensile strength parallel and perpendicular to the grain, modulus of rigidity, and transverse modulus of elasticity, by relating them to better-characterized properties.

Applications

ASTM D2555 is essential across multiple wood product sectors:

• Structural Lumber Engineering: Provides the baseline values for deriving working stresses used in construction design, ensuring the reliability and compliance of structural lumber.
• Engineered Wood Products: Supports accurate property assignment for laminated timbers, plywood, and round timbers, facilitating optimized design and efficient material use.
• Forest Resource Management: Enables assessment and utilization planning of wood species by supplying verifiable data on average strength properties at both species and regional levels.
• Product Specification and Marketing: Assists manufacturers and specifiers in assigning appropriate strength values to wood used in various products or regional markets, enhancing transparency and trust in wood product performance claims.
• Regulatory Compliance: Aligns with internationally recognized standardization principles, helping stakeholders meet regulatory and safety requirements, including those specified in international trade agreements.

Typical users include engineers, wood scientists, manufacturers, regulators, and trade professionals seeking accurate, standard-based data for wood species strength assessment.

Related Standards

• ASTM D143, Test Methods for Small Clear Specimens of Timber: Provides testing procedures foundational to ASTM D2555.
• ASTM D245, Practice for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber: Offers guidance for interpreting clear wood values in structural grading.
• ASTM D2915, Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products: Describes sampling and statistical analysis methods applicable to wood strength property determination.
• ASTM E105, Guide for Probability Sampling of Materials: Relevant for random sampling procedures.
• U.S. Forest Service Research Paper FPL 27: Source for wood density survey methods and data referenced in ASTM D2555.

By adhering to ASTM D2555, stakeholders ensure clear wood strength values are scientifically determined, comparable, and internationally recognized, supporting robust, safe, and efficient use of wood resources in construction and manufacturing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D2555 − 17a (Reapproved 2024)
Standard Practice for
Establishing Clear Wood Strength Values
This standard is issued under the fixed designation D2555; 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.
ε NOTE—Reference 4 was corrected editorially in February 2024.
INTRODUCTION
The development of safe and efficient design values for lumber, laminated timber, plywood, round
timbers, and other solid wood products, each with its own special requirements has, as a common
starting point, the need for an authoritative compilation of clear wood strength values for the
commercially important species. Also required are procedures for establishing, from these data, values
applicable to groups of species or to regional groupings within a species where necessitated by
marketing conditions. This practice has been developed to meet these needs and to provide, in
addition, information on factors for consideration in the adjustment of the clear wood strength values
to design values for engineering. Since factors such as species preference, species groupings,
marketing practices, design techniques, and safety factors vary with each type of product and end use,
it is contemplated that this practice will be supplemented where necessary by other appropriate
standards relating to specific design values for each such product. Practice D245 is an example of such
a standard applicable to the interpretation of the clear wood strength values in terms of allowable
properties for visually graded lumber.
A primary feature of this practice is the establishment of tables presenting the most reliable basic
information developed on the strength of clear wood and its variability through many years of testing
and experience. The testing techniques employed are those presented in Test Methods D143. Among
the recognized limitations of such strength data are those resulting from the problems of sampling
material from forests extending over large regions, and the uneconomical feasibility of completely
testing an intensive sample. A practical approach to the improvement of strength data is through the
application of the results of density surveys in which the specific gravity of the entire forest stand for
each species is determined on a sound statistical basis. Through regression equations derived from
presently available strength data, revised strength values are established from the specific gravity-
strength relationship for clear wood. This procedure greatly extends current capabilities to develop
new estimates of strength and to improve or verify estimates made in the past.
1. Scope 1.1.2 Guidelines for the interpretation of the data in terms of
assigned values for combinations of species or regional divi-
1.1 This practice covers the determination of strength values
sions within a species to meet special marketing needs, and
for clear wood of different species in the unseasoned condition,
unadjusted for end use, applicable to the establishment of 1.1.3 Information basic to the translation of the clear wood
design values for different solid wood products such as lumber, values into design values for different solid wood products for
laminated wood, plywood, and round timbers. Presented are:
different end uses.
1.1.1 Procedures by which test values obtained on small
1.1.4 For species where density survey data are not as yet
clear specimens may be combined with density data from
available for the re-evaluation of average strength properties,
extensive forest surveys to make them more representative,
the presently available data from tests made under the sampling
methods and procedures of Test Methods D143 or Practice
1 E105 are provided with appropriate provision for their appli-
This practice is under the jurisdiction of ASTM Committee D07 on Wood and
are the direct responsibility of Subcommittee D07.02 on Lumber and Engineered
cation and use. Because of the comprehensive manner in which
Wood Products.
the density survey is undertaken, it follows that the re-
Current edition approved Feb. 1, 2024. Published February 2024. Originally
evaluated strength data are intended to be representative of the
approved in 1966. Last previous edition approved in 2017 as D2555 – 17a. DOI:
10.1520/D2555-17AR24E01. forest stand, or rather large forest subdivisions.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D2555 − 17a (2024)
1.1.5 Some useful mechanical properties (tensile strengths to present the data on woods grown in the United States and on
parallel and perpendicular to grain, modulus of rigidity for a woods grown in Canada.
longitudinal-transverse plane, and transverse modulus of elas-
ticity) have not been extensively evaluated. Methods are 4. Procedure for Establishing Clear Wood Strength
described for estimating these properties by their relation to
Values
other properties.
4.1 Method A—Six steps are involved in establishing
1.2 The values stated in inch-pound units are to be regarded
strength values by the wood density survey procedure. These
as standard. The values given in parentheses are mathematical are: conducting the wood density survey, development of unit
conversions to SI units that are provided for information only
areas, determination of average specific gravity for a unit area,
and are not considered standard. determination of strength-specific gravity relations, estimation
of average strength properties for a unit area, and combining
1.3 This standard does not purport to address all of the
values for unit areas into basic groups and establishing average
safety concerns, if any, associated with its use. It is the
strength properties and estimates of variance for the groups. In
responsibility of the user of this standard to establish appro-
these methods a basic group is a combination of unit areas
priate safety, health, and environmental practices and deter-
representing a species or a regional division thereof.
mine the applicability of regulatory limitations prior to use.
4.1.1 Conducting Wood Density Survey—A well-designed
1.4 This international standard was developed in accor-
and thorough wood density survey is required to provide
dance with internationally recognized principles on standard-
needed data on specific gravity for the reevaluation of strength
ization established in the Decision on Principles for the
properties. Such a survey requires consideration of the geo-
Development of International Standards, Guides and Recom-
graphic range to be covered, the representativeness of the
mendations issued by the World Trade Organization Technical
sample, the techniques of density evaluation, and adequate data
Barriers to Trade (TBT) Committee.
analysis.
2. Referenced Documents
NOTE 2—Detailed information on an acceptable method of conducting
wood density surveys, together with survey data, are presented in the U.S.
2.1 ASTM Standards:
Forest Service Research Paper FPL 27 (1).
D143 Test Methods for Small Clear Specimens of Timber
4.1.2 Development of Unit Areas—Subdivide the geographi-
D245 Practice for Establishing Structural Grades and Re-
cal growth range of each species into unit areas that contain
lated Allowable Properties for Visually Graded Lumber
1 % or more of the estimated cubic foot volume of standing
D2915 Practice for Sampling and Data-Analysis for Struc-
timber of the species and are represented by reliable estimates
tural Wood and Wood-Based Products
of specific gravity of at least 20 trees. Make up unit areas of
E105 Guide for Probability Sampling of Materials
U.S. Forest Service Survey Units, or similar units or subdivi-
sions of units, for which reliable estimates of timber volume
3. Summary of Methods
are available. Develop unit areas objectively by means of the
3.1 Two methods are presented for establishing tables of
following steps:
clear wood strength properties for different species and re-
4.1.2.1 Select a base survey unit or subdivision of a survey
gional subdivisions thereof in the unseasoned condition and
unit to be grouped with others,
unadjusted for end use. These are designated Method A and
4.1.2.2 Group with similar adjacent areas to make up a unit
Method B.
area on the basis of a timber volume, and
3.1.1 Method A provides for the use of the results of surveys
4.1.2.3 Determine the number of tree specific gravity
of wood density involving extensive sampling of forest trees,
samples available in the proposed unit area.
in combination with the data obtained from standard strength
tests made in accordance with Test Methods D143. The NOTE 3—The rules for developing unit areas should represent an effort
to subdivide objectively and uniquely the range of a species into small
average strength properties are obtained from wood density
geographic areas, which are assumed to be considerably more homoge-
survey data through linear regression equations establishing the
neous with respect to the mechanical properties of the species than is the
relation of specific gravity to the several strength properties.
entire range itself. The number of unit areas associated with a species is
a function of the volume of timber on the smallest usable areas and the
NOTE 1—Density surveys have been completed for only a limited
number of tree specific gravity samples taken. In general, the larger the
number of species. Data are thus not currently available for the use of
range and the greater the commercial importance of the species, the
Method A on all commercial species. As such data become available they
greater are the number of unfit areas. One acceptable procedure for
will be incorporated in revisions of this practice.
establishing unit areas is presented in Appendix C of U.S. Forest Service
3.1.2 Method B provides for the establishment of tables of Research Paper FPL 27 (1).
strength values based on standard tests of small clear speci-
4.1.3 Determination of Average Specific Gravity for a Unit
mens in the unseasoned condition for use when data from
Area—Calculate the average specific gravity of trees in each
density surveys are not available. Separate tables are employed
unit area as the simple average of individual estimates of
specific gravity of trees within the unit area.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
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D2555 − 17a (2024)
4.1.4 Determination of Strength-Specific Gravity average strength properties for a group of unit areas for a
Relations—From matched specific gravity and strength data on species or a subdivision thereof by the following equation:
small clear specimens of wood, establish relationships of the
% ¯
Y 5 ~Y V /V! (2)
(i i i
form:
where:
y 5 a1bx (1)
= weighted average strength property for the group of
Y
where:
unit areas,
y = estimated strength value,
¯
Y = average strength property for the ith unit area,
i
a, b = constants for the species, and
V = percentage of standing timber volume of the species for
I
x = specific gravity of the species.
the ith unit area, and
V = total percentage of standing timber volume of the
for each species, using standard statistical methods of
species in the group of unit areas being combined.
regression analysis. Equations for modulus of rupture, modulus
of elasticity, maximum crushing strength, and maximum shear-
4.1.6.2 Compute the variability index, which is a measure of
ing strength are established in this manner. The distribution of the homogeneity among average values for unit areas within a
specific gravity in the samples used to compute regressions
group, by dividing the group average by the lowest unit area
should be representative of the species and, in particular, shall average included in the group.
represent the full specific gravity range. The nature of the true 4.1.6.3 Estimate a standard deviation, providing a measure
distribution of specific gravity can be obtained from results of of the dispersion of individual strength values about the group
average, for each basic group of unit areas using information
wood density surveys. Obtain the data from specimens tested
on variance obtained from density survey and standard strength
in accordance with Test Methods D143.
data. Compute estimates of standard deviation for each prop-
4.1.4.1 Several methods are available for securing suitable
erty as:
samples for obtaining data to compute strength-specific gravity
relationships, as follows: strength and specific gravity values 2 2 2
s 5 =b s 1s 1RMS (3)
~ !
w a
from samples obtained in conformance with Test Methods
where:
D143 may be employed solely or in combination with data
s = standard deviation
secured by sampling techniques described below or test
b = slope of the strength-specific gravity relation,
samples may be obtained from the forest resource in the form
s = within-tree variance in specific gravity esti-
of trees, logs, or lumber. Select samples that are representative w
mated from data used to obtain strength-
of all growing stock from each of at least five different
specific gravity relations,
locations within the growth range of a species that include the
s = among-tree variance in specific gravity ob-
a
scope of environmental conditions of the range. This implies
tained from density survey data,
that the sample from a single location must be such that all of
2 2
(s + s ) = estimate of total variance in specific gravity,
w a
the growing stock from that location is represented.
and
4.1.4.2 Where relationships between strength and specific
RMS = residual mean square from the strength-specific
gravity are shown to have a statistically significant difference at
gravity relation.
the 5 % level within a species growth range, subdivide the
NOTE 4—When a sampling technique is used that ensures only one
range to permit the development of more accurate estimating specimen will be taken per tree (such as a suitably designed mill sample),
2 2
the quantity (s + s ) is automatically obtained as a total variance of
equations for each subdivision. Develop equations for subdi-
w a
specific gravity.
visions of a species growth range only if specimens from at
NOTE 5—An alternative procedure for developing average strength
least five distinctly different places in the proposed subdivision
values where all unit areas are contained within a single species or
are available and if the correlation coefficients from the
regional subdivision thereof consists of combining the volume weighted
unit area specific gravities to establish a species or regional subdivision
strength-specific gravity regressions are 0.50 or greater.
specific gravity and then computing the average strength properties by
4.1.5 Estimation of the Average Strength Properties for a
substituting the average specific gravity in the strength-specific gravity
Unit Area—Given a set of strength-specific gravity estimating
regression equations.
equations for each species or subdivision thereof, compute
4.1.6.4 Average compression perpendicular to the grain
average strength properties for each unit area using these
values have not been developed by the procedures described in
equations and the average specific gravity for the unit area.
the preceding paragraphs but are based on available standard
4.1.6 Combining Unit Areas into Basic Groups and Devel-
strength data alone as in Method B.
opment of Average Strength Properties and Estimates of
4.1.6.5 Table 1 gives basic information on the strength
Variance for the Groups—Combine all unit areas containing
properties of the commercially important species for which
timber whose properties are described by the same strength-
wood density survey data are available. Listed are averages and
specific gravity relationships to produce a basic group of unit
standard deviations for modulus of rupture, modulus of
areas. Develop the following information for these basic
elasticity, maximum crushing strength parallel to grain, hori-
groups:
zontal shear strength, proportional limit in compression per-
4.1.6.1 For each unit area, obtain, from reliable volume pendicular to grain, and specific gravity. These properties are
data, the volume of the species being considered and estimate for clear wood in the unseasoned condition. Variability indexes
strength properties from appropriate equations. Determine are given for the first four properties.
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D2555 − 17a (2024)
TABLE 1 Clear Wood Strength Values Unadjusted for End Use and Measures of Variation for Commercial Species of Wood in the
A
Unseasoned Condition (Method A)
NOTE 1—All digits retained in the averages and standard deviations through the units position to permit further computation with minimum round-off
error (specific gravity excepted).
Property
Compression,
D
Perpendicular to Grain
Compression
Modulus of Modulus of
Parallel to Grain, Shear Strength Specific Gravity
B C Stress at Stress
Species or Rupture Elasticity
Crushing Strength
Proportional at
Region,
Limit 0.04 in.
or Both
Std.
Varia- Std. Avg., Varia- Varia- Std. Varia- Std. Std. Varia-
Avg., Dev., Avg., Avg., Avg., Avg., Std.
bility Dev., 1000 bility bility Dev., bility Dev., Dev., Avg. bility
E
psi 1000 psi psi psi psi Dev.
Index psi psi Index Index psi Index psi psi Index
psi
F
Douglas fir:
Coast 7665 1.05 1317 1560 1.05 315 3784 1.05 734 904 1.03 131 382 107 700 0.45 . 0.057
Interior West 7713 1.03 1322 1513 1.04 324 3872 1.04 799 936 1.02 137 418 117 707 0.46 . 0.058
Interior North 7438 1.04 1163 1409 1.04 274 3469 1.04 602 947 1.03 126 356 100 669 0.45 . 0.049
Interior South 6784 1.01 908 1162 1.00 200 3113 1.01 489 953 1.00 153 337 94 578 0.43 . 0.045
White fir 5854 1.01 949 1161 1.02 249 2902 1.02 528 756 1.01 78 282 79 491 0.37 . 0.045
California red fir 5809 1.01 885 1170 1.01 267 2758 1.01 459 767 1.00 146 334 94 573 0.36 . 0.043
Grand fir 5839 1.03 680 1250 1.03 164 2939 1.04 363 739 1.04 97 272 76 475 0.35 . 0.043
Pacific silver fir 6410 1.07 1296 1420 1.05 255 3142 1.06 591 746 1.05 114 225 63 414 0.39 . 0.058
Noble fir 6169 1.07 966 1380 1.08 310 3013 1.08 561 802 1.04 136 274 77 478 0.37 . 0.043
Western hemlock 6637 1.03 1088 1307 1.02 258 3364 1.03 615 864 1.02 105 282 79 457 0.42 . 0.053
Western larch 7652 1.04 1001 1458 1.02 249 3756 1.04 564 869 1.03 85 399 112 676 0.48 . 0.048
Black cottonwood 4890 1.00 951 1083 1.00 197 2200 1.00 360 612 1.00 92 165 46 305 0.31 . 0.034
Southern pine:
Loblolly 7300 1.08 1199 1402 1.08 321 3511 1.09 612 863 1.05 112 389 109 661 0.47 1.06 0.053
Longleaf 8538 1.07 1305 1586 1.07 295 4321 1.07 707 1041 1.05 120 479 134 804 0.54 1.05 0.058
Shortleaf 7435 1.04 1167 1388 1.04 268 3527 1.05 564 905 1.05 125 353 99 573 0.47 1.05 0.051
Slash 8692 1.09 1127 1532 1.08 295 3823 1.07 547 964 1.05 128 529 148 883 0.54 1.09 0.062
A
For tension parallel and perpendicular to grain, modulus of rigidity, and transverse modulus of elasticity see 4.3.
B
Modulus of rupture values are applicable to material 2 in. (51 mm) in depth.
C
Modulus of elasticity values are applicable at a ratio of shear span to depth of 14.
D
Based on a 2-in. wide steel plate bearing on the center of a 2-in. wide by 2-in. thick by 6-in. long specimen oriented with growth rings parallel to load.
E
A coefficient of variation of 28 % can be used as an approximate measure of variability of individual values about the stresses tabulated.
F
The regional description of Douglas fir is that given on pp. 54–55 of U.S. Forest Service Research Paper FPL 27 (1).
4.2 Method B: dition as determined from standard strength tests of small clear
4.2.1 Base average strength properties for clear wood of specimens. Table 2 covers data on woods grown in the United
species for which density survey data are not available on States, and Table 3 woods grown in Canada.
standard strength test data obtained in accordance with Test
4.3 Tensile strength parallel and perpendicular to grain,
Methods D143. Estimate approximate standard deviations for
modulus of rigidity associated with a longitudinal-transverse
these species as follows:
plane, and transverse modulus of elasticity are sometimes
%
needed for design considerations. These properties have not
s 5 cY (4)
been evaluated extensively. They may, however, be estimated
where:
from the clear wood properties of any combination of species,
s = standard deviation,
as described in the following criteria:
= the average value for the species, and
4.3.1 Tension Parallel to Grain—For clear wood strength in
Y
tension parallel to grain, the clear wood strength value for
c = 0.16 for modulus of rupture,
modulus of rupture may be used.
0.22 for modulus of elasticity,
4.3.2 Tension Perpendicular to Grain—For the average
0.18 for maximum crushing strength parallel to grain,
green clear wood strength in tension perpendicular to grain,
0.14 for maximum shear strength,
0.33 times the average green clear wood shear strength value
0.28 for compression perpendicular to grain strength,
shall be permitted.
and
0.10 for specific gravity.
NOTE 6—The value of tensile strength perpendicular to grain obtained
by this conversion applies to small clear wood specimens with cross
Alternatively, calculate the average strength properties for
sectional dimensions of 1 in. × 2 in. (25 mm × 51 mm) at mid-height.
clear wood and standard deviations from data from a random
sample obtained in accordance with Practice E105. 4.3.3 Modulus of Rigidity—For clear wood modulus of
4.2.2 Table 2 and Table 3 present basic information on the rigidity, 0.069 times the modulus of elasticity shall be permit-
strength properties of various species in the unseasoned con- ted.
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D2555 − 17a (2024)
1 11 11 1
NOTE 7—The factor 0.069 is ⁄16 times ⁄10 where the ⁄10 converts the the ⁄16 is an empirically determined ratio of shear modulus to elastic
apparent moduli of elasticity tabulated in this practice to true moduli, and modulus.
TABLE 2 Clear Wood Strength Values Unadjusted for End Use and Measures of Variation for Commercial Species of Wood in the
A
Unseasoned Condition (Method B) (for Woods Grown in the United States)
NOTE 1—All digits retained in the averages and standard deviations through the units position to permit further computation with minimum round-off
error (specific gravity excepted).
NOTE 2—Values of standard deviation have been calculated using the values for c given in 4.2.
Property
Compression,
D
Compression
Perpendicular to Grain
Modulus of Modulus of
Parallel to Grain, Shear Strength Specific Gravity
B C
Species (Official Common Rupture Elasticity
Stress at Pro- Stress at
Crushing Strength
Tree Names)
portional Limit 0.04 in.
Std. Avg., Std. Std. Std. Std.
Avg., Avg., Avg., Avg., Avg., Std.
Dev., 1000 Dev., Dev., Dev., Dev., Avg.
E
psi psi psi psi psi Dev.
psi psi 1000 psi psi psi psi
SOFTWOODS
Baldcypress 6640 1062 1184 260 3580 644 812 114 403 113 683 0.43 0.043
Cedar:
Alaska 6450 1032 1135 260 3050 549 842 118 349 98 597 0.42 0.042
Incense 6220 995 840 185 3150 567 834 117 369 103 629 0.35 0.035
Port Orford 6598 860 1297 247 3145 397 842 122 301 71 521 0.39 0.034
Atlantic white 4740 758 752 165 2390 430 694 97 244 68 430 0.31 0.031
Northern white 4250 680 643 141 1990 358 616 86 234 66 414 0.29 0.029
Eastern red 7030 1125 649 143 3570 643 1008 141 700 196 1155 0.46 0.046
Western red 5184 761 939 223 2774 493 771 115 244 65 430 0.31 0.027
Fir:
Balsam 5517 552 1251 143 2631 283 662 83 187 31 340 0.32 0.025
Subalpine 4900 664 1052 182 2301 363 696 103 192 44 348 0.31 0.032
Hemlock:
Eastern 6420 1027 1073 236 3080 554 848 119 359 101 613 0.39 0.039
Mountain 6270 1003 1038 228 2880 518 933 131 371 104 632 0.42 0.042
Pine:
Jack 6030 965 1068 235 2950 531 754 106 296 83 513 0.40 0.040
Eastern white 4930 789 994 219 2440 439 678 95 218 61 389 0.35 0.035
Lodgepole 5490 878 1076 237 2610 470 685 96 252 71 443 0.39 0.039
Monterey 6625 1060 1420 312 3330 599 875 123 440 123 742 0.46 0.046
Ponderosa 5130 821 997 219 2450 441 704 99 282 79 491 0.39 0.039
Red 5820 931 1281 282 2730 491 686 96 259 73 454 0.42 0.042
Sugar 4893 663 1032 193 2459 386 718 105 214 43 382 0.34 0.027
Western white 4688 693 1193 257 2434 406 677 98 192 46 348 0.35 0.034
Pine, southern yellow:
Pitch 6830 1093 1200 264 2950 531 860 120 365 102 622 0.47 0.047
Pond 7450 1192 1281 282 3660 659 936 131 441 123 743 0.51 0.051
Spruce 6004 1102 1002 286 2835 580 895 136 279 95 486 0.41 0.041
Sand 7500 1200 1024 225 3440 619 1143 160 450 126 757 0.46 0.046
Virginia 7330 1173 1218 268 3420 616 888 124 390 109 662 0.46 0.046
Redwood:
Old growth 7500 1202 1177 259 4210 758 803 112 424 119 716 0.39 0.039
Second growth 5920 947 955 210 3110 560 894 125 269 75 470 0.34 0.034
Spruce:
Black 6118 759 1382 193 2836 417 739 79 242 34 427 0.38 0.028
Engelmann 4705 692 1029 207 2180 427 637 64 197 50 358 0.33 0.033
Red 6003 627 1328 145 2721 313 754 95 262 59 459 0.37 0.025
Sitka 5660 906 1230 271 2670 481 757 106 279 78 486 0.38 0.038
White 4995 878 1141 265 2349 439 636 68 210 51 402 0.33 0.034
Tamarack 7170 1147 1236 272 3480 626 863 121 389 109 661 0.49 0.049
HARDWOODS
Alder, red 6540 1044 1167 257 2960 484 770 108 250 70 440 0.38 0.038
Ash:
Black 6000 960 1043 229 2300 414 861 120 347 97 594 0.45 0.045
Green 9460 1514 1400 308 4200 756 1261 176 734 206 1209 0.53 0.053
White 9500 1520 1436 316 3990 718 1354 190 667 187 1102 0.54 0.054
´1
D2555 − 17a (2024)
TABLE 2 Continued
Property
Compression,
Compression D
Perpendicular to Grain
Modulus of Modulus of
Parallel to Grain, Shear Strength Specific Gravity
B C
Species (Official Common Rupture Elasticity
Stress at Pro- Stress at
Crushing Strength
Tree Names)
portional Limit 0.04 in.
Std. Avg., Std. Std. Std. Std.
Avg., Avg., Avg., Avg., Avg., Std.
Dev., 1000 Dev., Dev., Dev., Dev., Avg.
E
psi psi psi psi psi Dev.
psi psi 1000 psi psi psi psi
Aspen:
Bigtooth 5400 864 1120 246 2500 450 732 102 206 58 370 0.36 0.036
Quaking 5130 821 860 189 2140 385 656 92 181 51 272 0.35 0.035
Basswood, American 4960 794 1038 228 2220 400 599 84 170 48 313 0.32 0.032
Beech, American 8570 1371 1381 304 3550 639 1288 180 544 152 907 0.57 0.057
Birch:
Paper 6380 1021 1170 257 2360 425 836 117 273 76 476 0.48 0.048
Sweet 9390 1502 1650 363 3740 673 1245 174 473 132 794 0.60 0.060
Yellow 8260 1322 1504 331 3380 608 1106 155 428 120 723 0.55 0.055
Cottonwood:
Eastern 5260 842 1013 223 2280 410 682 95 196 55 354 0.37 0.037
Elm:
American 7190 1150 1114 245 2910 524 1002 140 355 99 607 0.46 0.046
Rock 9490 1518 1194 263 3780 680 1274 178 610 171 1012 0.57 0.057
Slippery 8010 1282 1232 271 3320 598 1106 155 415 116 702 0.49 0.049
Hackberry 6480 1037 954 210 2650 477 1070 150 399 112 676 0.49 0.049
Hickory:
Pecan 9770 1563 1367 301 3990 718 1482 207 777 218 1277 0.61 0.061
Water 10740 1718 1563 344 4660 839 1440 202 881 247 1442 0.63 0.063
Mockernut 11080 1773 1574 346 4480 806 1277 179 812 227 1333 0.64 0.064
Pignut 11740 1878 1652 363 4810 866 1370 192 923 258 1509 0.67 0.067
Shagbark 11020 1763 1566 344 4580 824 1520 213 843 236 1382 0.64 0.064
Shellbark 10530 1685 1343 295 3920 706 1186 166 808 226 1326 0.63 0.063
Bitternut 10280 1645 1399 308 4570 823 1237 173 799 224 1312 0.62 0.062
Nutmeg 9060 1450 1289 284 3980 716 1032 144 760 213 1250 0.56 0.056
Magnolia:
Cucumbertree 7420 1187 1565 344 3140 565 991 139 330 92 567 0.44 0.044
Southern magnolia 6780 1085 1106 243 2700 486 1044 146 462 129 777 0.46 0.046
Maple:
Bigleaf 7390 1182 1095 241 3240 583 1108 155 449 126 756 0.44 0.044
Black 7920 1267 1328 292 3270 589 1128 158 601 168 997 0.52 0.052
Sugar 9420 1507 1546 340 4020 724 1465 205 645 181 1067 0.57 0.057
Red 7690 1230 1386 305 3280 590 1151 161 405 113 686 0.50 0.050
Silver 5820 931 943 207 2490 448 1053 147 369 103 629 0.44 0.044
Oak, red:
Black 8220 1315 1182 260 3470 625 1222 171 706 198 1164 0.56 0.056
Cherrybark 10850 1736 1790 394 4620 832 1321 185 765 214 1258 0.60 0.060
Northern red 8300 1328 1353 298 3440 619 1214 170 614 172 987 0.56 0.056
Southern red 6920 1107 1141 251 3030 545 934 131 547 153 912 0.53 0.053
Laurel 7940 1270 1393 306 3170 571 1182 165 573 160 953 0.56 0.056
Pin 8330 1333 1318 290 3680 662 1293 181 715 200 1179 0.58 0.058
Scarlet 10420 1667 1476 325 4090 736 1411 198 834 234 1368 0.61 0.061
Water 8910 1426 1552 341 3740 673 1240 174 620 174 1028 0.56 0.056
Willow 7400 1184 1286 283 3000 540 1184 166 611 171 1013 0.55 0.055
Oak, white:
Chestnut 8030 1285 1372 302 3520 634 1212 170 532 149 888 0.58 0.058
Live 11930 1909 1575 346 5430 977 2210 309 2039 571 3282 0.81 0.081
Post 8080 1293 1086 239 3480 626 1278 179 855 239 1401 0.60 0.060
Swamp chestnut 8480 1357 1350 297 3540 637 1262 177 573 160 953 0.60 0.060
White 8300 1328 1246 274 3560 641 1249 175 671 188 1109 0.60 0.060
Bur 7180 1149 877 193 3290 592 1354 190 677 190 1118 0.60 0.060
Overcup 8000 1280 1146 252 3370 607 1315 184 539 151 899 0.56 0.056
Swamp white 9860 1578 1593 350 4360 785 1296 181 764 214 1256 0.64 0.064
Poplar, balsam 3860 618 748 165 1690 304 504 71 136 38 259 0.30 0.030
´1
D2555 − 17a (2024)
TABLE 2 Continued
Property
Compression,
Compression D
Perpendicular to Grain
Modulus of Modulus of
Parallel to Grain, Shear Strength Specific Gravity
B C
Species (Official Common Rupture Elasticity
Stress at Pro- Stress at
Crushing Strength
Tree Names)
portional Limit 0.04 in.
Std. Avg., Std. Std. Std. Std.
Avg., Avg., Avg., Avg., Avg., Std.
Dev., 1000 Dev., Dev., Dev., Dev., Avg.
E
psi psi psi psi psi Dev.
psi psi 1000 psi psi psi psi
Sweetgum 7110 1138 1201 264 3040 547 992 139 367 103 626 0.46 0.046
Sycamore, American 6470 1035 1065 234 2920 526 996 139 365 102 622 0.46 0.046
Tanoak 10470 1675 1550 341 4650 837 . . . . . 0.58 0.058
Tupelo:
Black 7040 1126 1031 227 3040 547 1098 154 485 136 813 0.47 0.047
Water 7300 1168 1052 231 3370 607 1194 167 480 134 805 0.46 0.046
Yellow-poplar 5950 952 1222 269 2660 479 792 111 269 75 470 0.40 0.040
A
For tension parallel and perpendicular to grain, modulus of rigidity, and transverse modulus of elasticity, see 4.3.
B
Modulus of rupture values are applicable to material 2 in. (51 mm) in depth.
C
Modulus of elasticity values are applicable at a ratio of shear span to depth of 14.
D
Based on a 2-in. wide steel plate bearing on the center of a 2-in. wide by 2-in. thick by 6-in. long specimen oriented with growth rings parallel to load.
E
A coefficient of variation of 28 % can be used as an approximate measure of variability of individual values about the stresses tabulated.
4.3.4 Transverse Modulus of Elasticity—For clear wood group members in a particular shipment, the assigned values
transverse modulus of elasticity, 0.055 times the modulus of shall reflect the probability of obtaining the higher strength as
elasticity shall be permitted. well as the lower strength members as the combination is used.
If a portion of a combination is separately identified and
NOTE 8—Transverse modulus of elasticity is based on the standard
marketed to utilize fully its higher properties, the effect of such
compression perpendicular to grain specimen configuration in Test Meth-
ods D143 with load applied to the radial surface. The factor 0.055 is ⁄20 a separation shall be recognized by a re-evaluation of the
11 11
times ⁄10 where the ⁄10 converts the apparent moduli of elasticity,
remainder of the combination to assure that it also is marketed
determined using Test Methods D143 flexure testing, to true moduli. The
in accordance with its lower properties.
factor of ⁄20 is the empirically determined ratio of transverse modulus of
elasticity to true modulus of elasticity for Douglas-fir and represents an
5.2 Combinations of Table 1 Species (Method A):
approximate average value across commercially important species tabu-
5.2.1 The modulus of elasticity value assigned to any
lated in this practice.
combination of species and regional subdivisions of a species
5. Procedures for Assigning Values to Combinations
shall be the weighted average value for all species or regional
subdivisions thereof included in the combination, subject to the
5.1 General Requirements—Administrative and marketing
following limitations:
considerations often make it necessary or desirable to combine
basic groups having relatively similar properties into a single
NOTE 9—The weighted average modulus of elasticity and compression
marketing combination. When species are to be combined, it is
perpendicular to grain values are obtained by weighting the Table 1 values
in proportion to the volume of standing timber in accordance with the data
necessary to give consideration to the species within the
of Table 4, and then dividing the weighted values by the total volume they
combination having the lowest strength and stiffness proper-
represent.
ties. This can be done by setting limits that determine when a
5.2.1.1 The modulus of elasticity value assigned to the
species may be included in a combination without reducing the
combination shall not be more than 16 % greater than the
average properties for the combination. If a species is to be
lowest average value for any unit area included in the combi-
included and the limits are exceeded, the assigned property
nation. The average modulus of elasticity for the lowest unit
value for the combination must be reduced to a value such that
area of any species or subdivisions thereof may be computed
the limits are not exceeded. In any combination of species,
from the information in Table 1. It is the quotient of the average
equitable treatment for each species in the combination is
modulus of elasticity divided by the associated variability
assured by using a weighting factor based on the standing
index (see 4.1.6.2).
timber volume of that species in relation to the total standing
5.2.1.2 A species for which no timber volume data are
timber volume of the combination. Table 4 and Table 5 list
available may be included in a previously established combi-
cubic foot timber volume data for some commercially impor-
nation if the modulus of elasticity of the new species equals or
tant species. The criteria in 5.1.1, 5.2, 5.3, and 5.4, based on
experience with past accepted species groupings, are for use in exceeds the value assigned to the existing combination.
developing clear wood strength and stiffness assignments for 5.2.2 Establish compression perpendicular to grain values
any combination of species or unit areas. for combinations as described in 5.3.1. Establish other strength
5.1.1 While strength values assigned to combinations under value assignments for combinations, which represent a value
these methods do not necessarily require mixing of all the associated with the lower 5 % exclusion limit, as follows:
´1
D2555 − 17a (2024)
TABLE 3 Clear Wood Strength Values Unadjusted for End Use and Measures of Variation for Commercial Species of Wood in the
A
Unseasoned Condition (Method B) (for Woods Grown in Canada)
NOTE 1—Information on the strength properties of additional hardwood species can be obtained from Department of Forestry, Canada, Publication No.
1104 (2).
NOTE 2—Values of standard deviation have been calculated using the values for c given in 4.2.
Property
Compression,
Compression
D
Perpendicular to Grain
Modulus of Modulus of Parallel to Grain, Specific
Species (Official Com- Shear Strength
B C
Rupture Elasticity Crushing Strength, Gravity
Fiber Stress at Stress at
mon
max
Proportional Limit 0.04 in.
Tree Names)
Std. Avg., Std. Std. Std. Std.
Avg., Avg., Avg., Avg., Avg., Std.
Dev., 1000 Dev., Dev., Dev., Dev., Avg.
D ,E
psi psi psi psi psi Dev.
psi psi 1000 psi psi psi psi
SOFTWOODS
Cedar:
Eastern (northern) 3860 618 515 113 1890 340 660 92 196 55 354 0.30 0.030
white
Western red 5300 848 1046 230 2780 500 696 97 279 78 486 0.31 0.031
Cypress, yellow 6640 1062 1336 294 3240 583 880 123 350 98 599 0.42 0.042
(Alaska cedar)
Douglas fir 7540 1206 1613 355 3610 650 922 129 460 129 773 0.45 0.045
Fir:
Alpine 5158 825 1258 277 2502 450 684 96 258 72 452 0.33 0.033
Amabilis (Pacific sil- 5480 877 1347 296 2770 499 714 100 234 66 414 0.36 0.036
ver)
Balsam 5290 846 1129 248 2440 439 679 95 243 68 429 0.34 0.034
Hemlock:
Eastern 6780 1085 1268 279 3430 617 914 128 404 113 684 0.40 0.040
Western 6960 1114 1476 325 3580 644 752 105 373 104 635 0.41 0.041
Larch, western 8680 1389 1654 364 4420 796 920 129 519 145 867 0.55 0.055
Pine:
Jack 6310 1010 1167 257 2950 531 822 115 335 94 575 0.42 0.042
Lodgepole 5650 904 1274 280 2860 515 724 101 276 77 481 0.40 0.040
Red 5010 802 1066 235 2370 427 711 100 281 79 489 0.39 0.039
Western white 4830 773 1187 261 2520 454 652 91 235 66 416 0.36 0.036
Ponderosa 5700 912 1130 249 2840 511 720 101 349 98 597 0.44 0.044
Eastern white 5140 822 1176 259 2590 466 635 89 238 67 421 0.36 0.036
Spruce:
Black 5870 939 1320 290 2760 497 796 111 300 84 519 0.41 0.041
Engelmann 5660 906 1251 275 2810 506 702 98 268 75 468 0.38 0.038
Red 5880 941 1325 292 2810 506 807 113 273 76 476 0.38 0.038
Sitka 5420 867 1370 301 2560 461 634 89 291 81 505 0.35 0.035
White 5100 816 1150 253 2470 445 670 94 245 69 432 0.35 0.035
Tamarack 6820 1091 1238 272 3130 563 919 129 413 116 699 0.48 0.048
HARDWOODS
Alder, red 6300 1008 1199 264 3020 544 911 128 360 101 614 0.37 0.037
Aspen:
Largetooth 5340 854 1082 238 2390 430 789 110 212 59 379 0.39 0.039
Quaking 5460 874 1307 288 2350 423 718 101 199 56 359 0.37 0.037
Birch, white 6850 1096 1450 319 2680 482 944 132 358 100 612 0.51 0.051
Cottonwood:
Black 4060 650 971 214 1860 335 558 78 101 28 202 0.30 0.030
Eastern 4740 758 869 191 1970 355 770 108 210 59 376 0.35 0.035
Poplar, balsam 5010 802 1151 253 2110 380 666 93 178 50 325 0.37 0.037
A
For tension parallel and perpendicular to grain, modulus of rigidity, and transverse modulus of elasticity, see 4.3.
B
Modulus of rupture values are applicable to material 2 in. (51 mm) in depth.
C
Modulus of elasticity values are applicable at a ratio of shear span to depth of 14.
D
Based on a 2-in. wide steel plate bearing on the center of a 2-in. wide by 2-in. thick by 6-in. long specimen oriented with growth rings parallel to load.
E
A coefficient of variation of 28 % can be used as an approximate measure of variability of individual values about the stresses tabulated.
´1
D2555 − 17a (2024)
TABLE 4 Standing Timber Volume for Commercially Important Species Grown in the United States
A, B A, B
Species Volume MMCF Species Volume MMCF
Alder, red 7764 Larch, western 5984
Ash 11 595 Maple:
Aspen: Black 52
Bigtooth 3974 Red 31 398
Quaking 17 445 Silver 1913
Baldcypress 4200 Sugar 21 950
C
Beech, American 9262 Oak:
Birch: Select red 22 867
Sweet 2601 Other red 42 455
Yellow 4008 Select white 29 776
Cedar: Other white 19 780
Alaska 105 Pine:
Atlantic white 311 Eastern white 13 483
Eastern red 1612 Jack 1561
Incense 3611 Lodgepole 28 420
Northern white 5354 Ponderosa 36 223
Port-Orford 272 Red 4084
Western red 7736 Southern yellow:
Cottonwood: Loblolly 57 990
Black 781 Longleaf 4795
Douglas-fir: Pitch 1436
Coast 58 722 Pond 1251
Interior West 19 761 Shortleaf 15 284
Interior North 30 020 Slash 10 891
Interior South 5779 Spruce 576
Fir: Virginia 7206
Balsam 5655 Sugar 3373
California red 3150 Western white 1227
Grand 11 134 Redwood 4631
Noble 1152 Spruce:
Pacific silver 5671 Black 1599
Subalpine 11 939 Engelmann 17 804
White 14 471 Red 4803
Hackberry 1133 Sitka 1470
Hemlock: White 1790
Eastern 8530 Sweetgum 18 388
Mountain 3040 Sycamore 2658
Western 20 894 Tamarack 1202
D
Hickory 7888 Tupelo 6507
Yellow-poplar 23 203
A
Million cubic feet.
B
Source: Miles, et al (3). The attribute of interest is volume of growing stock in timberland (cuft) (live growing stock volume $5” DBH, on timberland). Based on survey
data from 2000 or earlier.
C
Select white oaks are Quercus alba(white), Q. michauxii(swamp chestnut), Q. muehlenbergii(chinkapin), Q. durandiiDurand, Q. bicolor(swamp white), and Q.
macrocarpa(bur). Select red oaks are Q. rubra(northern red), Q. falcata var. pagodaefolia(cherry bark), and Q. shumardii(shumard). Other Red and White are from
Hardwoods of North America by Harry Alden. Definitions of other White are Q. garryana (Oregon White), Q. lyrata (overcup), Q. stellata (post), and Q. prinus (chestnut).
Other Reds are Q. falcate (southern red), Q. coccinea (scarlet), Q. kelloggi (California black), Q. laurifolia (laurel), Q. nigra (water), Q. nuttalli (nuttal), Q. palusris (pin),
Q. phellos (willow), and Q. velutina (black).
D
Includes black gum.
5.2.2.1 Strength values assigned to any combination of %
CDF 5 @~Y/V.I.! 2 A#/s (5)
species and regional subdivisions of a species shall not exceed
where:
the 5 % exclusion value of the combined frequency distribution
= average value for each species or basic group of unit
of all species or subdivisions included in the combination.
Y
areas of a species included in the combination,
5.2.2.2 Determine the 5 % exclusion value for a combina-
V.I. = variability index for each species or basic group of
tion of species and regional subdivisions of a species by adding
unit areas of a species included in the combination,
the areas under the volume weighted frequency distribution of
s = standard deviation for each species or basic group of
each species or subdivision thereof at successively higher
unit areas of a species included in the combination,
levels of strength until a value is obtained below which 5 % of
and
the area under the combined frequency distribution will fall.
A = the computed 5 % exclusion value of the combined
NOTE 10—An approximate value for the 5 % exclusion limit of a
frequency distribution.
combination can be obtained by computing the volume weighted average
5 % exclusion value for all included species or regional subdivisions
5.2.2.4 A species for which no timber volume data are
thereof from the appropriate standard deviations.
available may be included in a previously established combi-
5.2.2.3 In addition, the composite dispersion factor (CDF)
nation if the 5 % exclusion values of the new species equal or
(Eq 5) shall not be less than 1.18 for any included species or
exceed the strength property values assigned the combination.
subdivision thereof. For basic groups using Method A proce-
dure:
´1
D2555 − 17a (2024)
TABLE 5 Standing Timber Volume for Commercially Important
levels of strength until a value is obtained below which 5 % of
A
Species Grown in Canada
the area under the combined frequency distribution will fall
B B
Species Volume MMCF Species Volume MMCF
(Note 10).
Alder, red 1081 Hemlock:
5.3.2.3 In addition, the composite dispersion factor (CDF)
Eastern 46 231
shall not be less than 1.48 for Method B, as established by the
Aspen: Western 2108
Largetooth 11 179
following equation:
Quaking 53 952 Larch, western 2608
%
CDF 5 ~Y 2 A!/s ~see 5.2.2.3! (6)
Birch, white 14 049 Pine:
Red 1235
5.3.2.4 A species for which no timber volume data are
Cedar: Ponderosa 640
available may be included in a previously established combi-
Eastern (northern) 7686 Western white 657
white Eastern white 6779
nation if the 5 % exclusion values of the new species equals or
Western red 20 690 Jack 30 767
exceeds the strength property values assigned the combination.
Cypress, yellow 5494 Lodgepole 86 860
(Alaska cedar)
5.4 Combinations of Table 1 and Table 2 and Table 3
Poplar, balsam 15 426
Species (Methods A and B Combined):
Cottonwood:
Black 10 871 Spruce:
5.4.1 Establish compression perpendicular to grain values
Eastern 73 White 57 193
for combinations as described in 5.3.1. The modulus of
Black 140 539
elasticity value assigned to any combination involving species
Douglas Fir 26 171 Red 21 077
Sitka 12 231
analyzed by Method A and species analyzed by Method B shall
Fir: Engelmann 15 528
be the weighted average value for all species and regional
Amabilis 13 793
subdivisions thereof included in the combination and shall
...