ASTM D3737-18(2023)e1
(Practice)Standard Practice for Establishing Allowable Properties for Structural Glued Laminated Timber (Glulam)
Standard Practice for Establishing Allowable Properties for Structural Glued Laminated Timber (Glulam)
ABSTRACT
This practice details the standard procedures for establishing the allowable properties for structural glued laminated timber (glulam). Allowable properties include: stress indexes; stress modification factors associated with slop of grain; stresses for bending, tension and compression parallel to the grain; horizontal shear; compression perpendicular to the grain; radial tension and compression stresses in curved members; grade adjustment factors; modulus of elasticity; and modulus of rigidity. This practice is limited to the calculation of allowable properties subject to the given procedures for the selection and arrangement of grades of lumber of the species considered. It does not cover the requirements for production, inspection and certification, but in order to justify the allowable properties developed using procedures in this practice, manufacturers must conform to recognized manufacturing standards.
SCOPE
1.1 This practice covers the procedures for establishing allowable properties for structural glued laminated timber. Included are the allowable stresses for bending, tension and compression parallel to the grain, horizontal shear, compression perpendicular to the grain, and radial tension and compression in curved members. Also included are modulus of elasticity and modulus of rigidity.
1.2 This practice is limited to the calculation of allowable properties subject to the given procedures for the selection and arrangement of grades of lumber of the species considered.
1.3 Requirements for production, inspection and certification are not included, but in order to justify the allowable properties developed using procedures in this practice, manufacturers must conform to recognized manufacturing standards. Refer to ANSI A190.1 and CSA O122.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in SI units are mathematical conversions that are provided for information only and are not considered standard.
1.5 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.
1.6 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
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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.
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Designation: D3737 − 18 (Reapproved 2023)
Standard Practice for
Establishing Allowable Properties for Structural Glued
Laminated Timber (Glulam)
This standard is issued under the fixed designation D3737; 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—Editorial changes were made throughout in October 2023.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers the procedures for establishing
D9 Terminology Relating to Wood and Wood-Based Prod-
allowable properties for structural glued laminated timber.
ucts
Included are the allowable stresses for bending, tension and
D143 Test Methods for Small Clear Specimens of Timber
compression parallel to the grain, horizontal shear, compres-
D198 Test Methods of Static Tests of Lumber in Structural
sion perpendicular to the grain, and radial tension and com-
Sizes
pression in curved members. Also included are modulus of
D245 Practice for Establishing Structural Grades and Re-
elasticity and modulus of rigidity.
lated Allowable Properties for Visually Graded Lumber
1.2 This practice is limited to the calculation of allowable
D2395 Test Methods for Density and Specific Gravity (Rela-
properties subject to the given procedures for the selection and
tive Density) of Wood and Wood-Based Materials
arrangement of grades of lumber of the species considered.
D2555 Practice for Establishing Clear Wood Strength Values
D2915 Practice for Sampling and Data-Analysis for Struc-
1.3 Requirements for production, inspection and certifica-
tural Wood and Wood-Based Products
tion are not included, but in order to justify the allowable
D4761 Test Methods for Mechanical Properties of Lumber
properties developed using procedures in this practice, manu-
and Wood-Based Structural Materials
facturers must conform to recognized manufacturing standards.
D5456 Specification for Evaluation of Structural Composite
Refer to ANSI A190.1 and CSA O122.
Lumber Products
1.4 The values stated in inch-pound units are to be regarded
D6570 Practice for Assigning Allowable Properties for Me-
as standard. The values given in SI units are mathematical
chanically Graded Lumber
conversions that are provided for information only and are not
E105 Guide for Probability Sampling of Materials
considered standard.
2.2 Other Standards:
ANSI A190.1 Structural Glued Laminated Timber
1.5 This standard does not purport to address all of the
ANSI/AWC National Design Specification for Wood Con-
safety concerns, if any, associated with its use. It is the
struction
responsibility of the user of this standard to establish appro-
CSA O122 Structural Glued Laminated Timber
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Terminology
1.6 This international standard was developed in accor-
3.1 Definitions:
dance with internationally recognized principles on standard-
3.1.1 alternative lumber—laminated veneer lumber (LVL),
ization established in the Decision on Principles for the
laminated strand lumber (LSL), oriented strand lumber (OSL),
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
1 3
This practice is under the jurisdiction of ASTM Committee D07 on Wood and Available from APA – The Engineered Wood Association, Tacoma, WA 98466,
is the direct responsibility of Subcommittee D07.02 on Lumber and Engineered http://www.apawood.org.
Wood Products. Available from American Wood Council (AWC), 222 Catoctin Circle, SE, Suite
Current edition approved Oct. 1, 2023. Published November 2023. Originally 201, Leesburg, VA 20175, http://www.awc.org.
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approved in 1978. Last previous edition approved in 2018 as D3737 – 18 . DOI: Available from Canadian Standards Association (CSA), 5060 Spectrum Way,
10.1520/D3737-18R23E01. Mississauga, ON L4W 5N6, Canada, http://www.csa.ca.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D3737 − 18 (2023)
or parallel strand lumber (PSL) meeting the requirements of knot, away from the edge of the lumber to the cross-sectional
Specification D5456; or solid-sawn lumber that is produced area of the lumber (see Fig. 1).
according to Practice D6570 and the grading rules of the
3.1.10 GDE—ratio of the cross-sectional area of the local
applicable grading or inspection agency.
grain deviation, which may or may not be associated with a
3.1.2 E-rated lumber—lumber graded for use in manufac- knot, at the edge of the lumber to the cross-sectional area of the
turing structural glued laminated timber by nondestructive lumber (see Fig. 1).
measurement of a modulus of elasticity (E) and by visual
3.1.11 GDS—projected sum of all GDE and GDC values
inspection in accordance with the grading rules of the appli-
within a one-foot length of lumber as defined in Fig. 1.
cable grading or inspection agency.
3.1.12 KC—ratio of the cross-sectional area of a knot
3.1.3 glulam—term used to denote structural glued lami-
located away from the edge of the lumber to the cross-sectional
nated timber, which is a product made from suitably selected
area of lumber. When a knot at the edge of the wide face and
and prepared pieces of wood bonded together with an adhesive
a knot located away from the edge are in the same cross-
either in a straight or curved form with the grain of all pieces
section, the combination of the two shall be used in determin-
essentially parallel to the longitudinal axis of the member.
ing KC (see Fig. 2).
3.1.4 horizontally laminated timber—member designed to
3.1.13 KE—ratio of cross-sectional area of a knot at the
resist bending loads applied perpendicularly to the wide faces
edge of wide face of lumber to the cross-sectional area of the
of the laminations (referred to as bending about the x-x axis).
lumber (see Fig. 2).
3.1.5 lamination—layer of lumber within the glued lami-
3.1.14 SR —required strength ratio of the tension lamina-
tl
nated timber.
tion at the outermost fiber.
3.1.6 modulus of elasticity (E)—for laminating, E is desig-
nated in two categories to distinguish mode of measurement
4. Materials Requirements
and application.
4.1 Requirements for Laminations:
3.1.6.1 Long-Span E (LSE)—modulus of elasticity calcu-
4.1.1 Laminations of glulam shall be of lumber with net
lated from deflection measured in a flat-wise static bending test
thickness of 2 in. (5 cm) or less.
of lumber with a center-point loading and a span-to-depth ratio
4.1.2 Lumber is permitted to be joined end to end with
ℓ
( ⁄d) of approximately 100 or the modulus of elasticity obtained
structural end joints to form long-length laminations. End
from Practice D2555 and multiplied by the appropriate factors
joints shall be qualified and quality controlled in accordance
from Tables 1-6.
with a recognized manufacturing standard.
4.1.3 Lumber is permitted to be placed or joined side to side
3.1.6.2 member E (E , E , E )—allowable modulus of
axial x y
to form wide laminations.
elasticity values of the structural glued laminated member as
4.1.4 Dimension lumber used to form laminations shall be
defined in this practice.
visually graded or E-rated according to established grading
3.1.7 vertically laminated timber—member designed to re-
rules.
sist bending loads applied parallel to the wide faces of the
4.1.5 Alternative lumber material is permitted by demon-
laminations (referred to as bending about the y-y axis).
strating equivalence to a dimension lumber grade in accor-
3.1.8 visually graded lumber—lumber graded by visual
dance with Annex A1.
inspection in accordance with the grading rules of the appli-
4.1.6 For the analysis of a glulam layup, all laminations in
cable grading or inspection agency.
a single cross-section shall be of equal thickness.
3.1.9 GDC—ratio of the cross-sectional area of the local
4.1.7 The analytical procedures of this standard practice are
grain deviation, which may or may not be associated with a
based on specific lamination characteristics.
4.1.7.1 Lumber properties including knot size and
frequency, physical properties such as specific gravity, and
TABLE 1 Adjustment Factors for Clear Wood Stresses
(Practice D2555) mechanical properties such as modulus of elasticity shall be
based on measurements of 2 by 6 lumber for definition of grade
Seasoning
Multipliers for Average
Factor for a
characteristics.
th
or 5 Percentile
12 %
Property
4.1.7.2 The effect of decay or compression failures upon
Average
strength cannot be readily determined, thus these defects shall
Moisture
Softwoods Hardwoods
Content
be prohibited from laminating grades insofar as existing
Bending 0.476 0.435 1.35
inspection and grading technology permit. Firm white speck or
1 1
( ⁄2.1) ( ⁄2.3)
light white pocket is permissible in grades of lumber that
permit knots to occupy up to one third or more of the
Compression 0.526 0.476 1.75
1 1
parallel to grain ( ⁄1.9) ( ⁄2.1)
cross-section provided their extent in combination with knots
does not exceed that of the largest edge knot permitted. The
Modulus of elas- 1.095 1.095 1.20
1 1
ticity ( ⁄0.913) ( ⁄0.913) exception is that firm white speck and light white pocket shall
be excluded from end joints in tension members and the outer
Horizontal shear 0.244 0.222 1.13
10 % of the total depth on the tension side of bending
1 1
( ⁄4.1) ( ⁄4.5)
members.
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D3737 − 18 (2023)
TABLE 2 Bending Stress Index Based on Large Beam Tests and Modulus of Elasticity Values for Visually Graded Lumber
NOTE 1—Appendix X1 provides one method of developing new data.
B
Bending Stress Index Modulus of Elasticity
A
Species Growth Classification
psi MPa million psi MPa
Douglas Fir-Larch medium grain 3000 20.7 1.9 13 100
close grain 3250 22.4 2.0 13 800
dense 3500 24.1 2.1 14 500
C
Southern Pine coarse grain 2000 13.8 1.5 10 300
medium grain 3000 20.7 1.8 12 400
dense 3500 24.1 2.0 13 800
Hem-Fir medium grain 2560 17.7 1.7 11 700
D
dense 3000 20.7 1.8 12 400
A
Classification for “dense” wood shall follow Practice D245.
B
Values shown are based on full-size beam tests. As a result, these values incorporate the effects of some features such as grain deviations in lumber along with influences
of end and face bonding influences. Beams designed using these values and tested in accordance with Test Methods D198 will yield strength values such that the lower
th
5 percentile will exceed the design bending stress by a factor of 2.1 with 75 % confidence. Analysis of test data assumed a log-normal distribution. For unsymmetric
combinations, tests have shown that values up to 40 % higher than those listed may be applied to the compression side of bending members.
C
Also applicable to minor species of southern pine regardless of growth rate.
D
Specific gravity, based on oven-dry weight and volume at 12 % moisture content, must equal or exceed 0.39.
TABLE 3 Bending Stress Indexes and Compression Stress Index TABLE 6 Grade Adjustment Factors for Modulus of Elasticity
A
Parallel to Grain for E-Rated Lumber Used in Laminating
A
Bending Strength Ratio Adjustment Factor
Compression Stress
0.55 or greater 1.00
Bending Stress
Long
Index Parallel
A
Index 0.45 to 0.54 0.90
-Span, B,C
to Grain
0.44 or less 0.80
E, psi
psi MPa psi MPa
A
Determined in accordance with Practice D245.
1 600 000 2560 17.7 1900 13.1
1 900 000 3000 20.7 2400 16.5
2 100 000 3500 24.1 2800 19.3
2 300 000 4000 27.6 3100 21.4
(1) For dry service conditions, grades permitting knots up
A
Values shall be not higher than obtained by interpolation for intermediate E
to one half of the cross-section may contain streaks of
values.
B
compression wood occupying as much as 20 % of the cross-
Values are for 12-in. (0.30 m) deep members at 12 % moisture content (dry).
C
Values are for members at 12 % moisture content (dry) values.
section. Streaks of compression wood up to one eighth of the
cross-section may be permitted in other grades.
(2) For wet service conditions, or for pressure-treated
TABLE 4 Parallel-to-Grain Stress Modification Factors Associated
members, the conditions of 4.1.7.3 (1) apply except that
with Slope of Grain for Designing
compression wood is limited to 5 % of the cross-section of the
Glulam Combinations
laminations in tension members and in the outer 10 % of the
Stress Modification Factor
Slope of Grain total depth on the tension side of bending members.
Tension Compression
4.1.7.4 Lumber shall be free of shakes and splits that make
1:4 0.27 0.46
an angle of less than 45° with the wide face of the piece. Pitch
1:6 0.40 0.56
1:8 0.53 0.66
pockets shall be limited in size to the area of the largest knot
1:10 0.61 0.74
permitted, and pitch streaks shall be limited to one sixth of the
1:12 0.69 0.82
width of the lumber.
1:14 0.74 0.87
1:15 0.76 1.00
4.2 Requirements for Adhesives:
1:16 0.80 1.00
4.2.1 Adhesives for use in glulam shall be rigid (non-
1:18 0.85 1.00
1:20 1.00 1.00
elastomeric) to ensure composite action of the laminations and
shall be sufficiently strong to transfer stresses required by the
intended use of the member.
TABLE 5 Constant Used to Adjust Vertically Laminated Bending
4.2.2 Adhesives shall be sufficiently durable to provide
Strength Ratio
bond for the life of the glulam member in its expected service
Strength Ratio (SR ) C
1 1
environment.
0.45 or greater 1.238
0.40 1.292 4.3 Tension Laminations—for horizontally laminated bend-
0.35 1.346
ing members shall meet the requirements herein.
0.30 1.400
4.3.1 The results of full-size beam tests reported in Refs
0.26 or less 1.444
(1-3) have yielded an empirical relationship between the size
of knots in the tension zone and bending strength. This
relationship dictates that special grading considerations be
4.1.7.3 Compression wood (as defined in Terminology D9)
in readily identifiable and damaging form shall be limited in
The boldface numbers in parentheses refer to a list of references at the end of
accordance with 4.1.7.3 (1) and 4.1.7.3 (2). this practice.
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D3737 −
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