ASTM D7341-08

Standard Practice for Establishing Characteristic Values for Flexural Properties of Structural Glued Laminated Timber by Full-Scale Testing

SIGNIFICANCE AND USE
Full-scale bending testing is an effective way to determine flexural properties of structural glued laminated timber (glulam) beams. However, testing of large glulam members is cost prohibitive. Mathematical models, when confirmed by full-scale test results, are useful tools to assign flexural properties for glulam. This practice provides guidelines for sampling and testing full-scale glulam beams to determine their flexural properties and to validate mathematical models intended for use in assigning flexural design values.
SCOPE
1.1 This practice describes procedures for full scale testing of structural glued laminated timber (glulam) to determine or verify characteristic values used to calculate flexural design properties. Guidelines are given for: (1) testing individual structural glued laminated timber lay-ups (with no modeling), (2) testing individual glulam combinations (with limited modeling), and (3) validating models used to predict characteristic values.
1.2 This practice is limited to procedures for establishing flexural properties (MOR and MOE). Some of the principles for sampling and analysis presented may be applicable to other properties. However, other properties may require additional testing considerations that are beyond the scope of this practice.
1.3 This practice is not intended to supersede the provisions of Practice D 3737, but provides an alternative method for establishing characteristic values. Lay-up combinations developed in accordance with Practice D 3737 are not required to be governed by this standard.
Note 1—The models described by Practice D 3737 have been developed and modified based on more than 50 years of experience and many test programs. In some cases, however, it may be desirable to develop a new model based on other input properties or using lumber materials or grades not covered by that standard.
1.4 Details of production, inspection, and certification are beyond the scope of this document. However, for test results to be representative of production, quality control systems shall be in place to ensure consistent quality. Manufacturing shall conform to recognized manufacturing standards such as ANSI/AITC A190.1 or CSA O122.
1.5 Adjustments to characteristic values to determine reference values for design shall be in accordance with Practice D 2915 for allowable stress design (ASD) or Specification D 5457 for load and resistance factor design (LRFD).
1.6 Adjustments to ASD reference values for end-use conditions intended for design purposes shall be performed in accordance with Practice D 3737. The same adjustment factors shall apply to LRFD reference values, except that the ASD “load duration” factor shall be replaced by an appropriate LRFD “time effect” factor as determined in accordance with recognized industry practice.
1.7 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-Jan-2008
• ICS: 79.060.99 - Other wood-based panels
• Technical Committee: D07 - Wood
• Drafting Committee: D07.02 - Lumber and Engineered Wood Products

Relations

• Replaced By: ASTM D7341-09 - Standard Practice for Establishing Characteristic Values for Flexural Properties of Structural Glued Laminated Timber by Full-Scale Testing
• Effective Date: 01-Mar-2009

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:D7341–08
Standard Practice for
Establishing Characteristic Values for Flexural Properties of
Structural Glued Laminated Timber by Full-Scale Testing
This standard is issued under the fixed designation D 7341; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope accordance with Practice D 3737.The same adjustment factors
shall apply to LRFD reference values, except that the ASD
1.1 This practice describes procedures for full scale testing
“load duration” factor shall be replaced by an appropriate
of structural glued laminated timber (glulam) to determine or
LRFD “time effect” factor as determined in accordance with
verify characteristic values used to calculate flexural design
recognized industry practice.
properties. Guidelines are given for: (1) testing individual
1.7 This standard does not purport to address all of the
structural glued laminated timber lay-ups (with no modeling),
safety concerns, if any, associated with its use. It is the
(2) testing individual glulam combinations (with limited mod-
responsibility of the user of this standard to establish appro-
eling), and (3) validating models used to predict characteristic
priate safety and health practices and determine the applica-
values.
bility of regulatory limitations prior to use.
1.2 This practice is limited to procedures for establishing
flexural properties (MOR and MOE). Some of the principles
2. Referenced Documents
for sampling and analysis presented may be applicable to other
2.1 ASTM Standards:
properties. However, other properties may require additional
D 198 Test Methods of Static Tests of Lumber in Structural
testing considerations that are beyond the scope of this
Sizes
practice.
D 245 Practice for Establishing Structural Grades and Re-
1.3 This practice is not intended to supersede the provisions
lated Allowable Properties for Visually Graded Lumber
of Practice D 3737, but provides an alternative method for
D 2915 Practice for Evaluating Allowable Properties for
establishing characteristic values. Lay-up combinations devel-
Grades of Structural Lumber
oped in accordance with Practice D 3737 are not required to be
D 3737 Practice for Establishing Allowable Properties for
governed by this standard.
Structural Glued Laminated Timber (Glulam)
NOTE 1—The models described by Practice D 3737 have been devel-
D 4761 Test Methods for Mechanical Properties of Lumber
oped and modified based on more than 50 years of experience and many
and Wood-Base Structural Material
test programs. In some cases, however, it may be desirable to develop a
D 5456 Specification for Evaluation of Structural Compos-
new model based on other input properties or using lumber materials or
ite Lumber Products
grades not covered by that standard.
D 5457 Specification for Computing Reference Resistance
1.4 Details of production, inspection, and certification are
of Wood-Based Materials and Structural Connections for
beyond the scope of this document. However, for test results to
Load and Resistance Factor Design
be representative of production, quality control systems shall
D 6815 Specification for Evaluation of Duration of Load
be in place to ensure consistent quality. Manufacturing shall
and Creep Effects of Wood and Wood-Based Products
conform to recognized manufacturing standards such asANSI/
2.2 Other Standards:
AITC A190.1 or CSA O122.
ANSI/AITC A190.1 American National Standard for Wood
1.5 Adjustments to characteristic values to determine refer-
Products – Structural Glued Laminated Timber
ence values for design shall be in accordance with Practice
AITC Test T119 Full Size End Joint Tension Test
D 2915 for allowable stress design (ASD) or Specification
D 5457 for load and resistance factor design (LRFD).
1.6 Adjustments to ASD reference values for end-use con-
ditions intended for design purposes shall be performed in
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee D07 on Wood and Standards volume information, refer to the standard’s Document Summary page on
is the direct responsibility of Subcommittee D07.02 on Lumber and Engineered the ASTM website.
Wood Products. Available from theAmerican Institute of Timber Construction (AITC), 7012 S.
Current edition approved Feb. 1, 2008. Published February 2008. Revere Parkway Suite 140, Centennial, CO 80112, [e-mail]
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7341–08
CSA O122 Structural Glued Laminated Timber tested, it is necessary to relate the properties of the component
PS-20 Voluntary Product Standard, ALS laminations to the beam properties through the use of an
analytical model.
3. Terminology
4.1.2 Predictive Models—Models that will be used to de-
velop new combinations, predict characteristic values, and
3.1 Definitions of Terms Specific to This Standard:
assign design values shall be able to predict accurately these
3.1.1 apparent properties, n—Mechanical properties as re-
valuesforabroadrangeofcombinations.Theseresultsmustbe
lated to the actual cross-sectional dimensions of the structural
validated by full-scale tests according to appropriate test
glued laminated timber.
methods for the property of interest.
3.1.2 characteristic value, n—A test statistic from which
4.1.3 Single Combination—For comparing different lay-ups
design values can be derived by the application of appropriate
adjustment factors. For strength properties of structural glued and identifying critical sizes for testing within a single com-
bination, transformed section analysis is sufficient to predict
laminated timber, this value is typically a fifth percentile
estimate with 75 % confidence. For deformation-based prop- the stresses on each grade in the lay-up relative to the stresses
in the tested lay-up. No further modeling shall be required.
erties, such as modulus of elasticity, this value is represented
by the average value. Other statistics are permitted to be used 4.1.4 Single Lay-Up—All modeling requirements shall be
as characteristic values for input properties of laminations waived if the test results are limited to a single, well-defined
depending on the model. Characteristic values for structural lay-up (i.e., the number of laminations is fixed, the grades of
glued laminated timber are typically based on apparent prop- laminations are well defined, and the size (depth) tested is
erties. representative of the size intended for production).
3.1.3 combination, n—A series of lay-ups having similar
4.2 Minimum Model Inputs:
lamination properties (grades, species, and end joint strengths),
4.2.1 General—At a minimum, a suitable model shall be
similar percentages of grade placement in the areas of critical
based on defined lamination properties representative of the
stresses, and similar predicted properties, that are grouped
material used for each lamination and shall account for the
together for design purposes.
placement of different qualities of laminations throughout the
cross section.
NOTE 2—An example of a lay-up combination based on Practice
4.2.2 Lamination Properties—The model shall account for
D 3737 would be a 24F-V4 Douglas fir combination.
both lumber and end joint properties.
3.1.4 lay-up, n—The specific arrangement of well-defined
4.2.2.1 Lumber Grade—The species and grades of lumber
laminationgradesforasinglestructuralgluedlaminatedtimber
used in structural glued laminated timber shall be well defined
depth.
to ensure consistent performance between the grades used in
3.1.5 model, n—A mathematical method for predicting a
test members and future production members. Strength and
characteristicvalueforfull-scalelaminatedtimberbasedonthe
stiffness properties for the laminations shall be assigned
input properties of the individual laminations.
according to the lumber grade. For deterministic models, the
3.1.6 reference value, n—The characteristic value of a
properties assigned to the grade shall be a representative
material that has been adjusted by the procedures in Practice
characteristic value for the grade. For probabilistic models, a
D 2915 or Specification D 5457 for use in design equations,
parametric distribution of values shall be determined to repre-
but has not been adjusted for end-use conditions.
sent the grade.
3.1.7 structural glued laminated timber, n—Aproductmade
(1) Species—The species or groups of species permitted by
from suitably selected and prepared pieces of component
the grade shall be well defined and shall be represented in the
laminations, hereafter referred to as “lumber” in this practice
tested members.
but including sawn lumber, manufactured lumber, or structural
(2) Modulus of Elasticity—For each grade of lumber used,
composite lumber, bonded together with an adhesive, with the
the modulus of elasticity shall be determined in accordance
grainofallpiecesessentiallyparalleltothelongitudinalaxisof
with Test Methods D 198 or D 4761 or by the procedures of
the member.
Specification D 5456 or Practice D 245.
3.1.8 well-defined grade, n—A lumber grade with specific
(3) Strength—Strength values shall be assigned to each
limits on acceptable characteristics, such as knots, slope of
grade of lumber used in the laminated timber. Values shall be
grain, density, modulus of elasticity, tensile strength, etc., to
determined by testing in accordance with Test Methods D 198
ensure reproducibility in production.
or D 4761 or by the procedures of Specification D 5456 or
Practice D 245. Strength values are also permitted to be
4. Modeling Requirements
assigned to a grade zone based on its interaction with the beam
4.1 General:
as a whole. (For example, the I /I model used in Practice
K G
4.1.1 Purpose for Modeling—For test results to be appli-
D 3737 assigns strength values in this way.)
cable to structural glued laminated timber sizes that are not
(4) Creep—Structural composite lumber for use in struc-
tural glued laminated timber shall demonstrate creep perfor-
mance similar to solid wood as demonstrated by Specification
Available from Canadian Standards Association (CSA), 5060 Spectrum Way,
D 6815.
Mississauga, ON L4W 5N6, Canada, http://www.csa.ca.
4.2.2.2 End Joint Strength—The model shall include the
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. effect of end joints (if used) stressed in tension. Appropriate
D7341–08
end joint tensile strengths shall be determined by full-scale wider nor 2 in. narrower than the tested width, provided that
tension testing in accordance with AITC Test T119 and main- the selection (grading) criteria relative to the cross-sectional
tained through in-plant quality control procedures. sizeisthesameforeachwidth.Forverticallylaminatedbeams,
4.2.3 Arrangement of Grades (Lay-Up)—The arrangement the depth of test specimens shall be representative of intended
of laminations of varying quality throughout a laminated productionsizes,andthewidthshallbebasedonthenumberof
timber can significantly alter the stress distribution and perfor- laminations and shall be equal to the number of laminations
manceofthemember.Themodelshallaccountfortheseeffects intended for use in production.
if more than one grade of laminations is to be used. The
5.4.3 Sample Size—A minimum of 30 specimens shall be
placement of grades shall be well defined to ensure proper
required for each lay-up.
modeling and reproducibility in production.
5.4.4 Facilities—If the lay-up is intended to be produced in
4.3 Minimum Model Analyses:
multiple facilities, samples shall be obtained from enough
4.3.1 Transformed-Section Analysis—The stresses at the
plants to represent all major processing variables including
location of each change of grade in a cross section shall be
lumber characteristics and end joint strength.
determined using transformed section analysis. For determin-
5.5 Sampling Requirements for a Single Combination:
istic analyses, the average modulus of elasticity of each lumber
5.5.1 Lay-Ups and Sample Size—For horizontally lami-
grade shall be used. The use of probabilistic models with
nated beams, a minimum of two critical depths based on a
simulated values of modulus of elasticity is also acceptable.
transformed section analysis shall be selected for testing. The
4.3.2 Prediction of Properties—The model shall predict
lay-ups at the critical depths shall be representative of a group
characteristic values for the laminated timber’s apparent prop-
of similar lay-ups within the combination. A minimum of 15
erties, based on the input lamination properties. Additionally,
members per critical depth shall be tested with 30 or more
for strength properties, the model shall account for the possi-
members tested for the combination. For vertically laminated
bility of any grade of lamination in the member controlling the
beams, a minimum of two widths shall be tested including
strength of the timber. The model shall identify the critical or
members with 2 and 4 laminations.
controlling grade zone.
5.5.2 Specimen Size(s)—For horizontally laminated beams,
the width of test specimens shall be representative of intended
5. Testing Requirements
production sizes and the depth shall be determined by the
5.1 General—Full-scale member testing can be used to (1)
critical depths selected in 5.5.1. For horizontally laminated
establish the properties of a single lay-up, (2) determine the
beams, a single width is permitted to be considered represen-
properties of a combination, or (3) validate a model intended
tative of members with widths not more than 2 in. wider nor 2
for use in the prediction and assignment of characteristic
in. narrower than the tested width. For vertically laminated
values. Increased testing shall be required for validation of a
beams, the depth of test specimens shall be representative of
model, as compared to verifying the properties of a single
intended production sizes, and the widths shall be based on the
combination or lay-up. Standard production procedures shall
lamination thickness multiplied by the number of laminations.
be followed for the manufacture of all test specimens. Matched
5.5.3 Facilities—If the combination is intended to be pro-
end joint specimens shall be manufactured and tested in
duced in multiple facilities, samples shall
...