ASTM D2555-05a

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Designation:D2555–05a
Standard Practice for
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Establishing Clear Wood Strength Values
This standard is issued under the fixed designation D 2555; 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.
INTRODUCTION
The development of safe and efficient working stresses 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 standard 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
tothelevelofworkingstressesfordesign.Sincefactorssuchasspeciespreference,speciesgroupings,
marketing practices, design techniques, and safety factors vary with each type of product and end use,
it is contemplated that this standard will be supplemented where necessary by other appropriate
standardsrelatingtospecificworkstressesforeachsuchproduct.PracticeD 245isanexampleofsuch
a standard applicable to the interpretation of the clear wood strength values in terms of working
stresses for structural 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 D 143.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 Guidelinesfortheinterpretationofthedataintermsof
assigned values for combinations of species or regional divi-
1.1 Thispracticecoversthedeterminationofstrengthvalues
sions within a species to meet special marketing needs, and
for clear wood of different species in the unseasoned condition,
1.1.3 Information basic to the translation of the clear wood
unadjusted for end use, applicable to the establishment of
values into working stresses for different solid wood products
working stresses for different solid wood products such as
for different end uses.
lumber, laminated wood, plywood, and round timbers. Pre-
1.1.4 For species where density survey data are not as yet
sented are:
available for the re-evaluation of average strength properties,
1.1.1 Procedures by which test values obtained on small
thepresentlyavailabledatafromtestsmadeunderthesampling
clear specimens may be combined with density data from
methods and procedures of Test Methods D 143 or Practice
extensive forest surveys to make them more representative,
E 105 are provided with appropriate provision for their appli-
cationanduse.Becauseofthecomprehensivemannerinwhich
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This practice is under the jurisdiction of ASTM Committee D07 on Wood and
the density survey is undertaken, it follows that the re-
are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods
evaluated strength data are intended to be representative of the
and Properties.
forest stand, or rather large forest subdivisions.
Current edition approved Oct. 1, 2005. Published October 2005. Originally
approved in 1966. Last previous edition approved in 2005 as D 2555 – 05.
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D2555–05a
1.1.5 Some useful mechanical properties (tensile strengths strength properties and estimates of variance for the groups. In
parallel and perpendicular to grain and modulus of rigidity for these methods a basic group is a combination of unit areas
a longitu
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