ASTM D4761-19

Standard Test Methods for Mechanical Properties of Lumber and Wood-Based Structural Materials

SIGNIFICANCE AND USE
4.1 These test methods provide procedures that are applicable under true field conditions, such as in a plant with specimens not at moisture equilibrium.  
4.2 The data established by these test methods can be used as follows:  
4.2.1 Develop strength and stiffness properties for the population represented by the material being tested (that is, individual grades, grade combinations, species, species groups, or any other defined, identifiable sample).  
4.2.2 Confirm the validity of strength and stiffness properties for the population represented by the material being tested.  
4.2.3 Investigate the effect of parameters that have the potential to influence the strength and stiffness properties of the material, such as moisture content, temperature, knot size and location, or slope of grain.  
4.3 The procedures chosen in accordance with these test methods shall be fully documented in the report to facilitate correlation with test results obtained through the use of traditional procedures, such as those set forth in Test Methods D198.
SCOPE
1.1 These test methods cover the determination of the mechanical properties of stress-graded lumber and other wood-based structural materials.  
1.2 These test methods appear in the following order:    
Section  
Bending edge-wise  
6  
Bending flat-wise:  
Center-point loading  
7  
Third-point loading  
8  
Axial strength in tension  
9  
Axial strength in compression  
10  
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-Mar-2019
• ICS: 79.040 - Wood, sawlogs and sawn timber
• ICS: 79.060.01 - Wood-based panels in general
• Technical Committee: D07 - Wood
• Drafting Committee: D07.01 - Fundamental Test Methods and Properties

Relations

• Replaces: ASTM D4761-18 - Standard Test Methods for Mechanical Properties of Lumber and Wood-Based Structural Materials
• Effective Date: 01-Apr-2019
• Refers: ASTM D4442-20 - Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D4442-16 - Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
• Effective Date: 15-Nov-2016
• Refers: ASTM D4442-15 - Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
• Effective Date: 01-Jun-2015
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM D198-14e1 - Standard Test Methods of Static Tests of Lumber in Structural Sizes
• Effective Date: 01-Feb-2014
• Refers: ASTM D198-14 - Standard Test Methods of Static Tests of Lumber in Structural Sizes
• Effective Date: 01-Feb-2014
• Refers: ASTM D198-13 - Standard Test Methods of Static Tests of Lumber in Structural Sizes
• Effective Date: 01-Oct-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM D9-12 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Oct-2012
• Refers: ASTM D2915-10 - Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
• Effective Date: 01-Nov-2010
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E4-10 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2010
• Refers: ASTM D9-09ae1 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Nov-2009

Overview

ASTM D4761-19 provides standardized test methods for determining the mechanical properties of lumber and wood-based structural materials. Developed by ASTM International, this standard is widely used in the construction and wood products industries to assess the strength and stiffness of materials such as stress-graded lumber, sawn timber, laminated timbers, and composite members. Uniquely, the standard supports both laboratory and field testing, making it highly versatile for research, quality control, and production environments.

Key Topics

• Applicability Under Field Conditions: ASTM D4761-19 allows for mechanical property testing not only in controlled laboratory environments but also in field conditions, such as production plants, where specimens might not be at moisture equilibrium.
• Comprehensive Mechanical Testing: The standard details methods to measure various mechanical properties, including:
  • Bending (edge-wise and flat-wise, under both center-point and third-point loading)
  • Axial strength in tension
  • Axial strength in compression
• Influence of Material Parameters: It facilitates the investigation of factors affecting mechanical properties, such as:
  • Moisture content
  • Temperature
  • Knot size and location
  • Slope of grain
• Reporting and Documentation: Thorough documentation of test procedures is required to ensure results are comparable to traditional standards, such as ASTM D198.

Applications

ASTM D4761-19 is essential for organizations involved in the manufacture, specification, and quality assurance of lumber and wood-based structural materials. Its applications include:

• Strength and Stiffness Validation: Testing according to this standard helps develop and confirm mechanical property data used in structural design and for grading lumber and related products.
• Quality Control: The flexibility of conducting tests in field or production environments supports ongoing quality assurance, ensuring materials meet regulatory and engineering requirements.
• Research and Product Development: Researchers and manufacturers use ASTM D4761-19 to evaluate the impact of environmental or operational factors on the mechanical behavior of wood-based products.
• Compliance and Regulatory Approval: As an international standard, it serves as a basis for demonstrating compliance with building codes and regulations that reference mechanical performance characteristics of wood materials.

Related Standards

Several other ASTM standards and industry documents are referenced within ASTM D4761-19, providing a broader context for wood testing and terminology:

• ASTM D198: Test Methods of Static Tests of Lumber in Structural Sizes
• ASTM D9: Terminology Relating to Wood and Wood-Based Products
• ASTM D2915: Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
• ASTM D4442: Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
• ASTM D7438: Practice for Field Calibration and Application of Hand-Held Moisture Meters
• PS20: American Softwood Lumber Standard (NIST Voluntary Product Standard)

These related documents complement ASTM D4761-19 by establishing terminology, supporting data analysis, and setting product-specific guidelines.

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ASTM D4761-19 is a foundational standard in the field of wood engineering, empowering professionals to accurately assess and validate the mechanical performance of lumber and wood-based materials. By ensuring a consistent and reliable approach to testing, it supports safer structures and improved material quality across the global construction industry.

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.
Designation: D4761 − 19
Standard Test Methods for
Mechanical Properties of Lumber and Wood-Based
Structural Materials
This standard is issued under the fixed designation D4761; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Numerous evaluations of the mechanical properties of wood-based structural materials have been
satisfactorilyconductedsincethelate1920s,usingTestMethodsD198.Thosemethodsarebestsuited
to a laboratory environment and are adaptable to a variety of products such as stress-graded lumber,
sawn timber, laminated timbers, wood-plywood composite members, reinforced and pre-stressed
timbers.
The procedures presented in these test methods have been derived from those set forth in Test
Methods D198. They are intended primarily for application to stress-graded lumber, but can be used
for other wood-based structural materials as well.The procedures are more flexible than those inTest
Methods D198, making testing in a non-laboratory environment more feasible.Thus the test methods
can be used on production sites for field testing and quality control, as well as in laboratories for
research applications. Key differences from Test Methods D198 are the testing speed, the deflection-
measuringproceduresforspecimensunderload,andthedetailofdatareporting.Furthermore,thetest
methods do not require that specimens be loaded to failure.
Since these test methods allow latitude in testing procedures, the procedures used shall be fully
documented in the test report. It may also be desirable to correlate the results from tests carried out
according to these test methods with test results obtained using a traditional procedure, such as that
set forth in Test Methods D198.
1. Scope 1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover the determination of the
ization established in the Decision on Principles for the
mechanicalpropertiesofstress-gradedlumberandotherwood-
Development of International Standards, Guides and Recom-
based structural materials.
mendations issued by the World Trade Organization Technical
1.2 These test methods appear in the following order:
Barriers to Trade (TBT) Committee.
Section
Bending edge-wise 6
2. Referenced Documents
Bending flat-wise:
Center-point loading 7
2.1 ASTM Standards:
Third-point loading 8
D9Terminology Relating to Wood and Wood-Based Prod-
Axial strength in tension 9
Axial strength in compression 10
ucts
D198Test Methods of Static Tests of Lumber in Structural
1.3 This standard does not purport to address all of the
Sizes
safety concerns, if any, associated with its use. It is the
D2915Practice for Sampling and Data-Analysis for Struc-
responsibility of the user of this standard to establish appro-
tural Wood and Wood-Based Products
priate safety, health, and environmental practices and deter-
D4442Test Methods for Direct Moisture Content Measure-
mine the applicability of regulatory limitations prior to use.
ment of Wood and Wood-Based Materials
These test methods are under the jurisdiction of ASTM Committee D07 on
Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental
Test Methods and Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2019. Published May 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1988. Last previous edition approved in 2018 as D4761–18. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D4761-19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4761 − 19
D7438Practice for Field Calibration and Application of 6. BENDING EDGE-WISE—THIRD-POINT LOADING
Hand-Held Moisture Meters
6.1 Scope
E4Practices for Force Verification of Testing Machines
6.1.1 This test method provides procedures for the determi-
E6Terminology Relating to Methods of Mechanical Testing
nationofthestrengthandmodulusofelasticityofstress-graded
E177Practice for Use of the Terms Precision and Bias in
lumber and other wood-based structural materials in bending
ASTM Test Methods
3 edge-wise,wherethememberdepthistypicallygreaterthanor
2.2 Other Document:
equal to the member breadth.
NISTVoluntaryProductStandardPS20AmericanSoftwood
Lumber Standard
NOTE 2—The use of the terms “edge-wise” and “flat-wise” in these test
methods are intended to refer to the geometric limitations described
NOTE 1—The current version of PS20 is given as an example of a
above.Theyarenotintendedtomandatethatthe“joist,”“edge,”“flat,”or
product standard applicable to stress-graded lumber. Other product stan-
“plank” orientation of a composite product needs to be tested using a
dards may apply to stress-graded lumber. For wood-based structural
specific specimen geometry or protocol.
materials other than stress-graded lumber, relevant product standards may
apply.
6.2 Summary of Test Methods
6.2.1 The specimen is simply supported and loaded by two
3. Terminology
equal transverse concentrated loads equidistant from the reac-
3.1 Definitions—See Terminologies D9 and E6 and Prac-
tion points and each other. The specimen is loaded at a
tices E4 and E177 for definitions of terms used in these test
prescribed rate until failure occurs or a pre-selected load or
methods.
deflection is reached. The load and corresponding deflection
3.2 Definitions of Terms Specific to This Standard:
are recorded when bending stiffness is to be determined. Only
3.2.1 breadth—in a bending test, that dimension of the
the load is measured if the objective of the test is to determine
specimen in the direction perpendicular to the span and
the specimen strength.
perpendicular to the direction of an applied load.
6.3 Apparatus
3.2.2 depth—in a bending test, that dimension of the speci-
6.3.1 Testing Machine—A device that combines (1) a reac-
men in the direction perpendicular to the span and parallel to
tion frame to support the specimen, (2) a loading mechanism
the direction of an applied load.
for applying load at a specified rate, and (3) a force-measuring
3.2.3 span—in a bending test, the distance between the
apparatusthatcanbecalibratedtotheaccuracyrequirementsof
center lines of the pivot points upon which the specimen is
6.3.3.2 following the procedures outlined in Practices E4.
supported to accommodate a transverse load.
6.3.1.1 Load and Reaction Apparatus—The load and reac-
tion apparatus shall include bearing plates at the load and
4. Significance and Use
reactionpointsthatareatleastaswideasthespecimenbreadth
4.1 These test methods provide procedures that are appli-
and not exceeding the member depth in length. These bearing
cable under true field conditions, such as in a plant with
plates shall have eased edges and sufficient bearing length to
specimens not at moisture equilibrium.
avoid a localized crushing failure at the load and reaction
4.2 The data established by these test methods can be used
points. The apparatus shall also include appropriate
as follows:
mechanisms, such as rollers, to minimize the development of
4.2.1 Developstrengthandstiffnesspropertiesforthepopu-
axialforcesinthespecimen.Eachloadandreactionpointshall
lation represented by the material being tested (that is, indi-
includeanin-planepivotpoint.Bearingplatesandrollersshall
vidual grades, grade combinations, species, species groups, or
be initially centered about their pivot points.
any other defined, identifiable sample).
6.3.1.2 Loading Configuration—Thespecimenshallbesim-
4.2.2 Confirm the validity of strength and stiffness proper-
plysupportedandloadedbytwoequaltransverseconcentrated
tiesforthepopulationrepresentedbythematerialbeingtested.
loads equidistant from the reaction points and each other.
4.2.3 Investigate the effect of parameters that have the
NOTE3—Theapparentmodulusofelasticityvariesfordifferentloading
potentialtoinfluencethestrengthandstiffnesspropertiesofthe
configurations (see Practice D2915). While the loading configuration that
material, such as moisture content, temperature, knot size and
commonly serves as the basis for design assumes a uniformly distributed
location, or slope of grain.
load, a configuration with two concentrated loads symmetrically placed
within the span is usually more suitable for structural tests to determine
4.3 The procedures chosen in accordance with these test
bending capacity and develop related design values. This configuration
methods shall be fully documented in the report to facilitate
also produces a constant bending moment, free of shear, in the portion of
correlation with test results obtained through the use of
the specimen between the load points.
traditional procedures, such as those set forth in Test Methods
6.3.1.3 Lateral Supports—When necessary to restrict speci-
D198.
men out-of-plane displacement, lateral supports shall be used.
5. Precision and Bias
Specimens having a depth-to-breadth ratio of three or greater
are subject to lateral instability during loading and shall be
5.1 The precision and bias of these test methods have not
evaluated for adequate lateral support. Any provided lateral
yet been established.
supports shall restrain out-of-plane displacement, but allow
movement of the specimen in the direction of load application
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460. with minimal frictional or other in-plane restraint.
D4761 − 19
6.3.2 Deflection-MeasuringApparatus—Ameasurementde- length outside the span at an end reaction (overhang) exceeds
vice shall be used to monitor the deflection of the specimen tentimesthespecimendepth,reporttheamountofoverhangat
whenthebendingstiffnessistobedetermined.Deflectionshall each end reaction.
bepermittedtobemeasureddirectlyasthedisplacementofthe 6.4.2.2 The span depends on the purpose of the test pro-
loading head of the testing machine or as direct measurement
gram. It is customary to express the span as a multiple of the
of the specimen movement relative to the reaction frame at specimen depth. While spans that currently serve as a basis
mid-span. In the former case, deflection is expressed as the
suitable for testing range from 17 to 21 times the depth of the
averagedisplacementoftheload-bearingplateswithrespectto specimen, other spans shall be permitted.
the reaction-bearing plates. If, because of the design of the
NOTE 6—Practice D2915 gives an indication of the impact that varying
apparatus, the deflection measurement includes extraneous
span-to-depth ratios have upon the measured member stiffness.The depth
components, the deflection data shall be permitted to be
in this section refers to the relevant size specified in the size classification
of the applicable product standard. As an example for stress-graded
adjusted for such extraneous components. However, if the
lumber, the depth used to determine the span will typically be the dressed
extraneous components are an appreciable portion of the total
dry size specified in the size classification of the current version of PS20.
measurement, then the test apparatus shall be re-examined for
For example, 3.5 in. (89 mm) should be used to calculate the span-to-
its suitability. In all instances, the report shall include a
depth ratio for members with a nominal depth of 4 in.
complete description of test conditions, extraneous
6.4.3 Conditioning—Specimens shall be permitted to be
components, and data adjustment procedures.
tested as produced or conditioned (for example, temperature,
NOTE 4—Possible sources of extraneous components of deflection with
moisture content, or treatment), depending on the purpose of
either measurement type might include: flexure of the load and reaction
the test program. If the temperature of the specimens at the
frame components, slack or looseness in the fixture connections, crushing
time of testing is less than 45°F (7°C) or more than 90°F
of the material surface at the bearing plates, and/or geometric imperfec-
(32°C), that temperature shall be reported.
tions of the tested material. These factors typically result in an overesti-
mation of the member deflection and a conservative underestimation of
6.5 Procedure
the measured stiffness. Provided test results with extraneous components
6.5.1 Specimen Measurements:
are repeatable over the range of materials typically tested, adjustment
6.5.1.1 Before testing, measure and record the cross-
factors to remove this bias may be developed based upon matched
correlations for similar tests of similar materials using Test Methods
sectional dimensions of every specimen at the center of the
D198. As an alternative, a mid-span yoke-mounted deflection device
spanunlessanotherlocationismoreappropriatetothepurpose
similar to that described by Test Methods D198 may be used with these
of the test.
procedures to improve accuracy and mitigate the need for adjustment.
6.5.1.2 Following the test, measure the moisture content of
6.3.3 Accuracy:
the specimens at a location away from the ends and as close to
6.3.3.1 The two load points shall be located within 6 ⁄16 in.
the failure zone as practical in accordance with the procedures
(1.6mm)ofthepositiondeterminedinaccordancewith6.3.1.2
outlined inTest Methods D4442 or using a calibrated moisture
and 6.4.2.2.
meter according to Practice D7438. The number of moisture
6.3.3.2 The force-measuring apparatus shall be such as to
content samples shall be determined using Practice D7438
permit load measurements with an error not to exceed 61.0%
guidelines,withconsiderationoftheexpectedmoisturecontent
oftheloadforloadsgreaterthanorequalto1000lbf(4450N).
variability, and any related requirements in the referenced
Forloadssmallerthan1000lbf,theerrorshallnotexceed 610
product standards.
lbf (45 N).
6.5.2 Lengthwise Positioning—Thepositioningofthespeci-
6.3.3.3 The deflection-measuring apparatus shall be such as
men across the span with respect to specific specimen charac-
to permit deflection measurements with an error not to exceed
teristicsshallbeaddressedbyawithin-piecesamplingplanfor
61.0% of the deflection with deflections greater than or equal
the test program. The procedure shall be documented and the
to 0.150 in. (4 mm).
resulting specimen length shall comply with the provisions of
6.4.2. The plan shall also detail how the tension edge is
NOTE 5—Bending stiffness estimates obtained from total specimen
deflections of 0.150 in. (4 mm) or less have a significant measurement selected.
error component and are not recommended.
NOTE7—Twopossibleapproachesusedforlengthwisepositioningmay
6.3.3.4 The cross-sectional dimensions of the member shall
be to locate the specimen across the span without bias regarding defects
be measured to at least three significant figures. or to locate specific defects near the center of the span and to deliberately
or randomly position a defect at the tension or compression side of the
6.4 Specimen
specimen, depending upon the test objectives.
6.4.1 Cross Section—Unless the effect of cross-section
6.5.3 Speed of Testing—The test rate shall be such that the
modifications is a test evaluation objective, the specimen shall
sample target failure load is achieved in approximately 1 min.
be tested without modifying the dimensions of the commercial
It is recommended that the failure load be reached in not less
cross section.
than 10 s nor more than 10 min.
6.4.2 Length:
NOTE 8—Some caution is warranted here. A test rate to achieve the
6.4.2.1 The minimum specimen length shall be the span,
averagefailureloadforthesampleinapproximately1minwilldifferfrom
determined in accordance with 6.4.2.2, plus an extension
that to achieve a lower percentile load for the same sample in approxi-
beyond the center lines of the end reactions, such that the
mately 1 min.
specimenwillnotslipoffthebearingplatesattheendreactions
NOTE 9—For stress-graded lumber, a rate of motion of the testing
during the test. In cases where the unsupported specimen machine loading head of approximately 3 in. (76 mm)/min will usually
D4761 − 19
permit the test to be completed in the prescribed time for span-to-depth
7. BENDING FLAT-WISE—CENTER-POINT
ratios of 17:1 and in cases where the target failure load is the average
LOADING
failure load for the sample.
7.1 Scope
6.5.4 Load-Deflection Data—Obtain load-deflection data, if
7.1.1 This test method provides procedures for the determi-
required, using the apparatus specified in 6.3.2.
nation of long-span modulus of elasticity of lumber and other
NOTE 10—Load and deflection data should be captured to define the
wood-based structural materials in flat-wise bending under
linear stiffness and at least include the design load range of the product
center-point load, where the member breadth is typically
being tested. Capturing the data from 10 to 40% of the expected
greater than the member depth (Note 2).
maximum load is typically sufficient to achieve this goal. For stress-
graded lumber, data obtained for loads corresponding to maximum
7.2 Determination of Long-Span Modulus of Elasticity
stresses in the specimen ranging from 400 to 1000 psi (3 to 7 MPa) will
7.2.1 Long-span modulus of elasticity (E) is defined as the
usually be adequate for stiffness calculations.
modulus of elasticity calculated from deflection measured in a
6.5.5 Maximum Load—If the purpose of the test is to
flat-wise test with center point loading and a span-depth ratio
determine strength properties, record the maximum load at-
(L/h) of approximately 100 6 10.
tained in the test.
NOTE 14—The long-span E is sometimes used to estimate the member
NOTE11—Inproofloading,theintendedloadtargetmaynotbereached modulus of elasticity with minimized influence from shear deflection.
ormaybeexceededslightly.Thetargetloadshouldbereportedalongwith
7.3 Summary of the Test Method
the actual attained load.
7.3.1 A known concentrated transverse load is applied at
6.5.6 Record of Failure—For a destructive test, describe the
mid-span of a simply supported specimen oriented flatwise.A
characteristic causing failure, and its location within the span.
displacement measurement device is used to determine the
deflection of the specimen under the load. The modulus of
NOTE 12—An example of a coding scheme for recording characteristic
typeandfailurelocationinstress-gradedlumberisgiveninAppendixX1.
elasticity (E) is determined by relating the applied load and
deflection to the size of specimen and the span.
6.6 Report
6.6.1 The report content depends on the purpose of the test
7.4 Apparatus
program. The report shall include, at the minimum, the
7.4.1 Support System—Any support system shall be permit-
following information:
ted that provides unrestrained support at both end reactions.
6.6.1.1 Description of the testing machine, including a
The reaction point at one end shall be constructed so that
drawingorphotographofthetestsetup,thespan,fixturing,and
stability is provided for a piece of twisted lumber, such as a
the deflection-measuring apparatus, if applicable.
pedestal with a single point reaction, a reaction point that is
6.6.1.2 Description of calibration procedures, frequency,
designed to tilt to match the twist of the lumber, or special
and records.
shims that restrain the specimen from rocking on the reaction
6.6.1.3 Method used for the measurement of the moisture
supports. Each load or reaction point shall include an in-plane
content of specimens. pivot point. Bearing plates, when employed, shall be initially
6.6.1.4 Speedoftestingandmeansofcontrolofthespeedof
centered about their pivot points.
testing. 7.4.2 Accuracy
6.6.1.5 Specimens lengthwise positioning and selection of
7.4.2.1 Span—The load point shall be located within 6 ⁄16
the tension edge. in. (1.6 mm) of the position determined in accordance with
6.6.1.6 As applicable, the type of load-deflection data for 7.2.1 and 7.5.1.
the calculation of the stiffness of specimens, including a 7.4.2.2 Test Loads—Weights used for test loads shall be
descriptionoftestconditions,extraneouscomponents,anddata compact and known to an accuracy of 60.05 lbm (23 g).
adjustment procedures in accordance with 6.3.2.
7.4.2.3 Deflection-Measuring Apparatus—The specimen
6.6.1.7 Description of the population sampled, in accor- deflectionshallbemeasuredusingadevicewiththecapacityto
dance with Practice D2915. measure displacement up to at least 1 in. (25 mm) with an
6.6.1.8 Descriptionofthesample,including(1)samplesize, accuracy of 61%.
(2) conditioning, if applicable, (3) temperature of specimens at
7.4.2.4 The cross-sectional dimensions of the member shall
the time of testing, and (4) number of specimens that failed be measured to at least three significant figures.
during the test.
7.4.3 A weight of approximately 5.0 lbm. (2.3 kg) shall be
6.6.1.9 Data on specimens, including, as applicable, (1) used for pre-loading. Further weights in 5.0 or 10.0 lbm. (2.3
grade, (2) actual cross-sectional dimensions, (3) moisture to 4.5 kg) increments shall be used to apply test loads.
content, (4) overhang in accordance with 6.4.2.1,(5) load-
NOTE 15—Three 5-lbm. (2.3 kg) weights and one 10-lbm. (4.5 kg)
deflection data, (6) maximum load, (7) time to maximum load,
weight have been found to provide an adequate combination of weights
and (8) failure description and location.
for nominal 2 by 4 through nominal 2 by 12 surfaced dimension lumber
sizes.
NOTE 13—The Appendices of Test Methods D198 provide equations
7.5 Specimen
thatmaybeemployedtofurtherconvertthisdataintomodulusofrupture,
modulus of elasticity, and other useful normalized quantities depending
7.5.1 Cross Section—Unless the effect of cross-section
upon the test objectives.
modifications is a test evaluation objective, the specimen shall
6.6.1.10 Details of any deviations from the prescribed or be tested without modifying the dimensions of the commercial
recommended procedures as outlined in this test method. cross section.
D4761 − 19
7.5.2 Length—The minimum specimen length shall be the tant from the reaction points and each other. The specimen is
span, determined in accordance with 7.6.2 plus an extension loadedataprescribedrateuntilfailureoccursorapre-selected
beyond the center lines of the end reactions, such that the load or deflection is reached. The load and corresponding
specimenwillnotslipoffthebearingplatesattheendreactions deflection are recorded when bending stiffness is to be deter-
during the test. mined. Only the load is measured if the objective of the test is
7.5.3 Conditioning—The procedures of 6.4.3 shall be fol- to determine or verify the specimen strength.
lowed. 8.2.2 If the data collection is only to determine specimen
stiffness, then a step-wise load shall be permitted that includes
7.6 Procedure
pre-loading and then adding a known weight for deflection
7.6.1 Specimen Measurements—The procedures of 6.5.1
measurement.
shall be followed.
7.6.2 Space the reaction points to provide a span-to-depth 8.3 Apparatus
ratioforthespecimenofapproximately100 610foruseinthe 8.3.1 Testing Machine—A device that combines (1) a reac-
calculation of the modulus of elasticity.The span used shall be tion frame to support the specimen; (2) a loading mechanism
forapplyingloadataspecifiedrateorprescribedloadinterval;
recorded.
7.6.3 Place the displacement measurement device midway and (3) a force-measuring apparatus that can be calibrated to
between the reaction points and adjust it so the downward the requirements of 8.3.3.2, following the procedures outlined
deflection of the specimen can be measured when loaded. in Practices E4. If the test is used only to determine member
Construct or arrange the apparatus such that the relative bendingstiffnessusingknownweights,thenaforce-measuring
position of the deflection measurement device to the reaction device is not specifically required. Fig. 1 illustrates the
pointsisnotchangedmorethan0.001in.(0.025mm)whenthe traditional device meeting the requirements of these test
load weight is placed on the specimen. methods for bending stiffness measurement using a known test
7.6.4 Place the specimen flatwise on the reaction points and load.
in firm contact with both end reactions. 8.3.1.1 Load and Reaction Apparatus—The load and reac-
7.6.5 Apply the 5.0 lbm (2.3 kg) pre-load weight to the tion apparatus shall include bearing plates at the load and
specimen at or near mid-span and either tare the deflection reactionpointsthatareatleastaswideasthespecimenbreadth
measurement device or take an immediate reading. and not exceeding the member depth in length. These bearing
7.6.6 Load the specimen at mid-span and immediately take plates shall have eased edges and sufficient bearing length to
a deflection measurement device reading. This load shall be avoid a localized crushing failure at the load and reaction
such that it will induce approximately 0.2 in. (5 mm) or more points. The apparatus shall also include appropriate
deflection. mechanisms, such as rollers, to minimize the development of
7.6.7 Determine and record the deflection of the specimen axialforcesinthespecimen.Eachloadandreactionpointshall
due to the load applied in 7.6.6. include an in-plane pivot point. If only the bending stiffness is
7.6.8 Long-span modulus of elasticity is determined using to be determined in accordance with 8.2.2, then roller support
the following equation: surfaces similar to those depicted in Fig. 1 are permitted in
E 5 PL / 48∆I
~ !
where:
E = modulus of elasticity, psi (MPa),
P = increment of applied load in 7.6.6, lbf (N),
L = span, in. (mm),
∆ = increment of deflection from 7.6.7 corresponding to the
increment of applied load, in 7.6.6, in. (mm), and
4 4
I = moment of inertia, in. (mm ).
7.7 Report
7.7.1 The content of the report depends on the purpose of
the test program. The repor
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4761 − 18 D4761 − 19
Standard Test Methods for
Mechanical Properties of Lumber and Wood-Based
Structural Materials
This standard is issued under the fixed designation D4761; 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.
INTRODUCTION
Numerous evaluations of the mechanical properties of wood-based structural materials have been
satisfactorily conducted since the late 1920s, using Test Methods D198. Those methods are best suited
to a laboratory environment and are adaptable to a variety of products such as stress-graded lumber,
sawn timber, laminated timbers, wood-plywood composite members, reinforced and pre-stressed
timbers.
The procedures presented in these test methods have been derived from those set forth in Test
Methods D198. They are intended primarily for application to stress-graded lumber, but can be used
for other wood-based structural materials as well. The procedures are more flexible than those in Test
Methods D198, making testing in a non-laboratory environment more feasible. Thus the test methods
can be used on production sites for field testing and quality control, as well as in laboratories for
research applications. Key differences from Test Methods D198 are the testing speed, the deflection-
measuring procedures for specimens under load, and the detail of data reporting. Furthermore, the test
methods do not require that specimens be loaded to failure.
Since these test methods allow latitude in testing procedures, the procedures used shall be fully
documented in the test report. It may also be desirable to correlate the results from tests carried out
according to these test methods with test results obtained using a traditional procedure, such as that
set forth in Test Methods D198.
1. Scope
1.1 These test methods cover the determination of the mechanical properties of stress-graded lumber and other wood-based
structural materials.
1.2 These test methods appear in the following order:
Section
Bending edge-wise 6
Bending flat-wise:
Center-point loading 7
Third-point loading 8
Axial strength in tension 9
Axial strength in compression 10
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.
These test methods are under the jurisdiction of ASTM Committee D07 on Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental Test Methods
and Properties.
Current edition approved Nov. 1, 2018April 1, 2019. Published March 2019May 2019. Originally approved in 1988. Last previous edition approved in 20132018 as
D4761 – 13.D4761 – 18. DOI: 10.1520/D4761-18.10.1520/D4761-19.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4761 − 19
2. Referenced Documents
2.1 ASTM Standards:
D9 Terminology Relating to Wood and Wood-Based Products
D198 Test Methods of Static Tests of Lumber in Structural Sizes
D2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
D4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
D7438 Practice for Field Calibration and Application of Hand-Held Moisture Meters
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
2.2 Other Document:
NIST Voluntary Product Standard PS20 American Softwood Lumber Standard
NOTE 1—The current version of PS20 is given as an example of a product standard applicable to stress-graded lumber. Other product standards may
apply to stress-graded lumber. For wood-based structural materials other than stress-graded lumber, relevant product standards may apply.
3. Terminology
3.1 Definitions—See Terminologies D9 and E6 and Practices E4 and E177 for definitions of terms used in these test methods.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 breadth—in a bending test, that dimension of the specimen in the direction perpendicular to the span and perpendicular
to the direction of an applied load.
3.2.2 depth—in a bending test, that dimension of the specimen in the direction perpendicular to the span and parallel to the
direction of an applied load.
3.2.3 span—in a bending test, the distance between the center lines of the pivot points upon which the specimen is supported
to accommodate a transverse load.
4. Significance and Use
4.1 These test methods provide procedures that are applicable under true field conditions, such as in a plant with specimens not
at moisture equilibrium.
4.2 The data established by these test methods can be used as follows:
4.2.1 Develop strength and stiffness properties for the population represented by the material being tested (that is, individual
grades, grade combinations, species, species groups, or any other defined, identifiable sample).
4.2.2 Confirm the validity of strength and stiffness properties for the population represented by the material being tested.
4.2.3 Investigate the effect of parameters that have the potential to influence the strength and stiffness properties of the material,
such as moisture content, temperature, knot size and location, or slope of grain.
4.3 The procedures chosen in accordance with these test methods shall be fully documented in the report to facilitate correlation
with test results obtained through the use of traditional procedures, such as those set forth in Test Methods D198.
5. Precision and Bias
5.1 The precision and bias of these test methods have not yet been established.
6. BENDING EDGE-WISE—THIRD-POINT LOADING
6.1 Scope
6.1.1 This test method provides procedures for the determination of the strength and modulus of elasticity of stress-graded
lumber and other wood-based structural materials in bending edge-wise, where the member depth is typically greater than or equal
to the member breadth.
NOTE 2—The use of the terms “edge-wise” and “flat-wise” in these test methods are intended to refer to the geometric limitations described above.
They are not intended to mandate that the “joist,” “edge,” “flat,” or “plank” orientation of a composite product needs to be tested using a specific specimen
geometry or protocol.
6.2 Summary of Test Methods
6.2.1 The specimen is simply supported and loaded by two equal transverse concentrated loads equidistant from the reaction
points and each other. The specimen is loaded at a prescribed rate with observation of load and/or deflection until failure occurs
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 ASTM website.
Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.
D4761 − 19
or a pre-selected load or deflection is reached. The load and corresponding deflection are recorded when bending stiffness is to be
determined. Only the load is measured if the objective of the test is to determine the specimen strength.
6.3 Apparatus
6.3.1 Testing Machine—A device that combines (1) a reaction frame to support the specimen, (2) a loading mechanism for
applying load at a specified rate, and (3) a force-measuring apparatus that can be calibrated to the accuracy requirements of 6.3.3.2
following the procedures outlined in Practices E4.
6.3.1.1 Load and Reaction Apparatus—The load and reaction apparatus shall include bearing plates at the load and reaction
points that are at least as wide as the specimen breadth and not exceeding the member depth in length. These bearing plates shall
have eased edges and sufficient bearing length to avoid a localized crushing failure at the load and reaction points. The apparatus
shall also include appropriate mechanisms, such as rollers, to minimize the development of axial forces in the specimen. Each load
and reaction point shall include an in-plane pivot point. Bearing plates and rollers shall be initially centered about their pivot points.
6.3.1.2 Loading Configuration—The specimen shall be simply supported and loaded by two equal transverse concentrated loads
equidistant from the reaction points and each other.
NOTE 3—The apparent modulus of elasticity varies for different loading configurations (see Practice D2915). While the loading configuration that
commonly serves as the basis for design assumes a uniformly distributed load, a configuration with two concentrated loads symmetrically placed within
the span is usually more suitable for structural tests to determine bending capacity and develop related design values. This configuration also produces
a constant bending moment, free of shear, in the portion of the specimen between the load points.
6.3.1.3 Lateral Supports—When necessary to restrict specimen out-of-plane displacement, lateral supports shall be used.
Specimens having a depth-to-breadth ratio of three or greater are subject to lateral instability during loading and shall be evaluated
for adequate lateral support. Any provided lateral supports shall restrain out-of-plane displacement, but allow movement of the
specimen in the direction of load application with minimal frictional or other in-plane restraint.
6.3.2 Deflection-Measuring Apparatus—A measurement device shall be used to monitor the deflection of the specimen when
the bending stiffness is to be determined. Deflection shall be permitted to be measured directly as the displacement of the loading
head of the testing machine or as direct measurement of the specimen movement relative to the reaction frame at mid-span. In the
former case, deflection is expressed as the average displacement of the load bearing load-bearing plates with respect to the reaction
bearing reaction-bearing plates. If, because of the design of the apparatus, the deflection measurement includes extraneous
components, the deflection data shall be permitted to be adjusted for such extraneous components. However, if the extraneous
components are an appreciable portion of the total measurement, then the test apparatus shall be re-examined for its suitability. In
all instances, the report shall include a complete description of test conditions, extraneous components, and data adjustment
procedures.
NOTE 4—Possible sources of extraneous components of deflection with either measurement type might include: flexure of the load and reaction frame
components, slack or looseness in the fixture connections, crushing of the material surface at the bearing plates, and/or geometric imperfections of the
tested material. These factors typically result in an overestimation of the member deflection and a conservative underestimation of the measured stiffness.
Adjustment factors, if used to remove some of this conservatism,Provided test results with extraneous components are repeatable over the range of
materials typically tested, adjustment factors to remove this bias may be developed based upon matched correlations for similar tests of similar materials
using Test Methods D198. As an alternative, a mid-span yoke-mounted deflection device similar to that described by Test Methods D198 may be used
with these procedures to improve accuracy and mitigate the need for adjustment.
6.3.3 Accuracy:
6.3.3.1 The two load points shall be located within 6 ⁄16 in. (1.6 mm) of the position determined in accordance with 6.3.1.2 and
6.4.2.2.
6.3.3.2 The force-measuring apparatus shall be such as to permit load measurements with an error not to exceed 61.0 % of the
load for loads greater than or equal to 1000 lbf (4450 N). For loads smaller than 1000 lbf, the error shall not exceed 610 lbf (45
N).
6.3.3.3 The deflection-measuring apparatus shall be such as to permit deflection measurements with an error not to exceed
61.0 % of the deflection with deflections greater than or equal to 0.150 in. (4 mm).
NOTE 5—Bending stiffness estimates obtained from total specimen deflections of 0.150 in. (4 mm) or less have a significant measurement error
component and are not recommended.
6.3.3.4 The cross-sectional dimensions of the member shall be measured to an accuracy of at least three significant figures.
6.4 Specimen
6.4.1 Cross Section—Unless the effect of cross-section modifications is a test evaluation objective, the specimen shall be tested
without modifying the dimensions of the commercial cross section.
6.4.2 Length:
6.4.2.1 The minimum specimen length shall be the span, determined in accordance with 6.4.2.2, plus an extension beyond the
center lines of the end reactions, such that the specimen will not slip off the bearing plates at the end reactions during the test. In
cases where the unsupported specimen length outside the span at an end reaction (overhang) exceeds 10ten times the specimen
depth, report the amount of overhang at each end reaction.
D4761 − 19
6.4.2.2 The span depends on the purpose of the test program. It is customary to express the span as a multiple of the specimen
depth . depth. While spans that currently serve as a basis suitable for testing range from 17 to 21 times the depth of the specimen,
other spans shall be permitted. Practice D2915 gives an indication of the impact that varying span-to-depth ratios have upon the
measured member stiffness.
NOTE 6—Practice D2915The depth here gives an indication of the impact that varying span-to-depth ratios have upon the measured member stiffness.
The depth in this section refers to the relevant size specified in the size classification of the applicable product standard. As an example for stress-graded
lumber, the depth used to determine the span will typically be the dressed dry size specified in the size classification of the current version of PS20. For
example, 3.5 in. (89 mm) should be used to calculate the span-to-depth ratio for members with a nominal depth of 4 in. (102 mm).
6.4.3 Conditioning—Specimens shall be permitted to be tested as produced or conditioned (for example, temperature, moisture
content, or treatment), depending on the purpose of the test program. If the temperature of the specimens at the time of testing is
less than 45°F (7°C)45 °F (7 °C) or more than 90°F (32°C),90 °F (32 °C), that temperature shall be reported.
6.5 Procedure
6.5.1 Specimen Measurements:
6.5.1.1 Before testing, measure and record the cross-sectional dimensions of every specimen at the center of the span unless
another location is more appropriate to the purpose of the test.
6.5.1.2 Following the test, measure the moisture content of the specimens at a location away from the ends and as close to the
failure zone as practical in accordance with the procedures outlined in Test Methods D4442 or using a calibrated moisture meter
according to Practice D7438. The number of moisture content samples shall be determined using Practice D7438 guidelines, with
consideration of the expected moisture content variability, and any related requirements in the referenced product standards.
6.5.2 Lengthwise Positioning—The positioning of the specimen across the span with respect to specific specimen characteristics
shall be addressed by a within-piece sampling plan for the test program. The procedure shall be documented and the resulting
specimen length shall comply with the provisions of 6.4.2. The plan shall also detail how the tension edge is selected.
NOTE 7—Two possible approaches used for lengthwise positioning may be to locate the specimen across the span without bias regarding defects or
to locate specific defects near the center of the span and to deliberately or randomly position a defect at the tension or compression side of the specimen,
depending upon the test objectives.
6.5.3 Speed of Testing—The test rate shall be such that the sample target failure load is achieved in approximately 1 min. It is
recommended that the failure load be reached in not less than 10 s nor more than 10 min.
NOTE 8—Some caution is warranted here. A test rate to achieve the average failure load for the sample in approximately 1 min will differ from that
to achieve a lower percentile load for the same sample in approximately 1 min.
NOTE 9—For stress-graded lumber, a rate of motion of the testing machine loading head of approximately 3 in. (76 mm)/min will usually permit the
test to be completed in the prescribed time for span to depth span-to-depth ratios of 17:1 and in cases where the target failure load is the average failure
load for the sample.
6.5.4 Load-Deflection Data—Obtain load-deflection data, if required, using the apparatus specified in 6.3.2.
NOTE 10—Load and deflection data should be captured to define the linear stiffness and at least include the design load range of the product being
tested. Capturing the data from 10 to 40%40 % of the expected maximum load is typically sufficient to achieve this goal. For stress-graded lumber, data
obtained for loads corresponding to maximum stresses in the specimen ranging from 400 to 1000 psi (3 to 7 MPa) will usually be adequate for stiffness
calculations.
6.5.5 Maximum Load—If the purpose of the test is to determine strength properties, record the maximum load attained in the
test.
NOTE 11—In proof loading, the intended load target may not be reached or may be exceeded slightly. The target load should be reported along with
the actual attained load.
6.5.6 Record of Failure—For a destructive test, describe the characteristic causing failure, and its location within the span.
NOTE 12—An example of a coding scheme for recording characteristic type and failure location in stress-graded lumber is given in Appendix X1.
6.6 Report
6.6.1 The report content depends on the purpose of the test program. The report shall include, at the minimum, the following
information:
6.6.1.1 Description of the testing machine, including a drawing or photograph of the test setup, the span, fixturing, and the
deflection-measuring apparatus, if applicable.
6.6.1.2 Description of calibration procedures, frequency, and records.
6.6.1.3 Method used for the measurement of the moisture content of specimens.
6.6.1.4 Speed of testing and means of control of the speed of testing.
6.6.1.5 Specimens lengthwise positioning and selection of the tension edge.
6.6.1.6 As applicable, the type of load-deflection data for the calculation of the stiffness of specimens, including a description
of test conditions, extraneous components, and data adjustment procedures in accordance with 6.3.2.
6.6.1.7 Description of the population sampled, in accordance with Practice D2915.
D4761 − 19
6.6.1.8 Description of the sample, including (1) sample size, (2) conditioning, if applicable, (3) temperature of specimens at the
time of testing, and (4) number of specimens that failed during the test.
6.6.1.9 Data on specimens, including, as applicable, (1) grade, (2) actual cross-sectional dimensions, (3) moisture content, (4)
overhang in accordance with 6.4.2.1, (5) load-deflection data, (6) maximum load, (7) time to maximum load, and (8) failure
description and location.
NOTE 13—The Appendices of Test Methods D198 provide equations that may be employed to further convert this data into modulus of rupture,
modulus of elasticity, and other useful normalized quantities depending upon the test objectives.
6.6.1.10 Details of any deviations from the prescribed or recommended procedures as outlined in this test method.
7. BENDING FLAT-WISE—CENTER-POINT LOADING
7.1 Scope
7.1.1 This test method provides procedures for the determination of long-span modulus of elasticity of lumber and other
wood-based structural materials in flat-wise bending under center-point load, where the member breadth is typically greater than
the member depth (Note 2).
7.2 Determination of Long-Span Modulus of Elasticity
7.2.1 Long-span modulus of elasticity (E) is defined as the modulus of elasticity calculated from deflection measured in a
flat-wise test with center point loading and a span-depth ratio (L/h) of approximately 100610.100 6 10.
NOTE 14—The long-span E is sometimes used to estimate the member modulus of elasticity with minimized influence from shear deflection.
7.3 Summary of the Test Method
7.3.1 A known concentrated transverse load is applied at mid-span of a simply supported specimen oriented flatwise. A
displacement measurement device is used to determine the deflection of the specimen under the load. The modulus of elasticity
(E) is determined by relating the applied load and deflection to the size of specimen and the span.
7.4 Apparatus
7.4.1 Support System—Any support system shall be permitted that provides unrestrained support at both end reactions. The
reaction point at one end shall be constructed so that stability is provided for a piece of twisted lumber, such as a pedestal with
a single point reaction, a reaction point that is designed to tilt to match the twist of the lumber, or special shims that restrain the
specimen from rocking on the reaction supports. Each load or reaction point shall include an in-plane pivot point. Bearing plates,
when employed, shall be initially centered about their pivot points.
7.4.2 Accuracy
7.4.2.1 Span—The load point shall be located within 6 ⁄16 in. (1.6 mm) of the position determined in accordance with 7.2.1 and
7.5.1.
7.4.2.2 Test Loads—Weights used for test loads shall be compact and known to an accuracy of 60.05 lbm (23 g).
7.4.2.3 Deflection-Measuring Apparatus—The specimen deflection shall be measured using a device with the capacity to
measure displacement up to at least 1 in. (25 mm) with an accuracy of 61%.
7.4.2.4 The cross-sectional dimensions of the member shall be measured to at least three significant figures.
7.4.3 A weight of approximately 5.0 lbm. (2.3 kg) shall be used for pre-loading. Further weights in 5.0 or 10.0 lbm. (2.3 to 4.5
kg) increments shall be used to apply test loads.
NOTE 15—Three 5-lbm. (2.3 kg) weights and one 10-lbm. (4.5 kg) weight have been found to provide an adequate combination of weights for nominal
2 by 4 through nominal 2 by 12 surfaced dimension lumber sizes.
7.5 Specimen
7.5.1 Cross Section—Unless the effect of cross-section modifications is a test evaluation objective, the specimen shall be tested
without modifying the dimensions of the commercial cross section.
7.5.2 Length—The minimum specimen length shall be the span, determined in accordance with 7.6.2 plus an extension beyond
the center lines of the end reactions, such that the specimen will not slip off the bearing plates at the end reactions during the test.
7.5.3 Conditioning—The procedures of 6.4.3 shall be followed.
7.6 Procedure
7.6.1 Specimen Measurements—The procedures of 6.5.1 shall be followed.
7.6.2 Space the reaction points to provide a span-to-depth ratio for the specimen of approximately 100610 100 6 10 for use
in the calculation of the modulus of elasticity. The span used shall be recorded.
7.6.3 Place the displacement measurement device midway between the reaction points and adjust it so the downward deflection
of the specimen can be measured when loaded. Construct or arrange the apparatus such that the relative position of the deflection
measurement device to the reaction points is not changed more than 0.001 in. (0.025 mm) when the load weight is placed on the
specimen.
7.6.4 Place the specimen flatwise on the reaction points and in firm contact with both end reactions.
7.6.5 Apply the 5.0 lbm (2.3 kg) pre-load weight to the specimen at or near mid-span and either tare the deflection measurement
device or take an immediate reading.
D4761 − 19
7.6.6 Load the specimen at mid-span and immediately take a deflection measurement device reading. This load shall be such
that it will induce approximately 0.2 in. (5 mm) or more deflection.
7.6.7 Determine and record the deflection of the specimen due to the load applied in 7.6.6.
7.6.8 Long-span modulus of elasticity is determined using the following equation:
E 5 PL / 48ΔI
~ !
where:
E = modulus of elasticity, psi (MPa),
P = increment of applied load in 7.6.6, lbf (N),
L = span, in. (mm),
Δ = increment of deflection from 7.6.7 corresponding to the increment of applied load, in 7.6.6, in. (mm), and
4 4
I = moment of inertia, in. (mm ).
7.7 Report
7.7.1 The content of the report depends on the purpose of the test program. The report shall include, at the minimum, all
applicable information as presented in 6.6.
8. BENDING FLAT-WISE—THIRD-POINT LOADING
8.1 Scope
8.1.1 This test method provides procedures for the determination of bending strength and stiffness of stress-graded lumber and
other wood based wood-based structural materials in flat-wise bending on short spans under third-point load, where the member
breadth is typically greater than the member depth (Note 2).
8.2 Summary of the Test Methods
8.2.1 The specimen is simply supported and loaded on the wide face by two equal transverse concentrated loads equidistant
from the reaction points and each other. The specimen is loaded at a prescribed rate with observation of load and/or deflection until
failure occurs or a preselectedpre-selected load or deflection is reached. The load and corresponding deflection are recorded when
bending stiffness is to be determined. Only the load is measured if the objective of the test is to determine or verify the specimen
strength.
8.2.2 If the data collection is only to determine specimen stiffness, then a step-wise load shall be permitted that includes
pre-loading and then adding a known weight for deflection measurement.
8.3 Apparatus
8.3.1 Testing Machine—A device that combines ((1)1) a reaction frame to support the specimen; ((2)2) a loading mechanism
for applying load at a specified rate or prescribed load interval; and ((3)3) a force-measuring apparatus that can be calibrated to
the requirements of 8.3.3.2, following the procedures outlined in Practices E4. If the test is used only to determine member bending
stiffness using known weights, then a force-measuring device is not specifically required. Fig. 1 illustrates the traditional device
meeting the requi
...