ASTM D2718-00(2011)
(Test Method)Standard Test Methods for Structural Panels in Planar Shear (Rolling Shear)
Standard Test Methods for Structural Panels in Planar Shear (Rolling Shear)
SIGNIFICANCE AND USE
Planar shear (rolling shear) characteristics of structural panels determined by these test methods are essential for the rigorous design of various glued wood-panel structural components, such as box beams, folded plate roofs, and stressed skin panels. Planar shear also may govern the design at low span-depth ratios encountered in floors subjected to high concentrated loads, concrete forms at high pouring pressures, and bulk storage structures.
The modulus of rigidity determined from Test Method A is a composite of the entire specimen acting as a unit. For plywood panels for which the ratio between the shear moduli of the plies with grain oriented parallel and perpendicular to the shear forces is known, the rolling shear modulus of the perpendicular plies can be calculated.
Veneer produced by slicing or rotary peeling may contain fine checks or separations parallel to the grain on the knife side of the veneer that are produced as the knife is forced through the wood. These checks are termed “knife checks” to distinguish them from occasional checks that may be formed on the opposite side of the veneer by forces at the compression bar, and from checks caused by drying. Knife checks can have a significant effect on rolling shear properties in plywood panels and may be of significance in other veneer containing panels. Test Method A requires (when applicable) the testing of matching specimens having knife checks oriented both open and closed wherever possible (see Fig. 1).
To control or define other variables influencing rolling shear, these test methods require determination of moisture content, specific gravity, and elapsed time-to-failure. Conditioning of test material in controlled atmospheres, determination of depth of knife checks (when applicable), and determination of percent of wood and plywood glueline failure (when applicable) are recommended.
(a) Knife Checks Open (b) Knife Checks ClosedFIG. 1 Orientation of Knife Checks in Plywood
SCOPE
1.1 These test methods determine the shear properties of structural panels associated with shear distortion of the planes parallel to the edge planes of the panels. Both shear strength and modulus of rigidity may be determined. Primarily, the tests measure the planar shear (rolling shear) strength developed in the plane of the panel.
1.2 Structural panels in use include plywood, waferboard, oriented strand board, and composites of veneer and of wood-based layers.
1.3 Two test methods are included:
1.3.1 Test Method A—Planar shear loaded by plates.
1.3.2 Test Method B—Planar shear induced by five-point bending.
1.3.3 The choice of method will be dictated by the purpose of the test and equipment available.
1.3.4 Test Method A, Planar Shear Loaded by Plates—This test method uses a rectangular panel section adhered between steel plates with protruding knife edges to create load at the panel faces. This test method has been used to develop shear properties of plywood and oriented strand board for the purpose of confirming design values. This test method does not produce pure shear, but the specimen length is prescribed so that the secondary stresses have a minimum effect. The method determines shear strength and modulus of rigidity.
1.3.5 Test Method B, Planar Shear Induced by Five-Point Bending—Planar shear stress is induced on the panel while loaded in bending using two continuous spans. This test method determines planar shear strength consistent with panel applications under transverse loading. This test method is able to determine shear strength at any moisture condition.
1.4 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.
5.1 The specimen having the form of a rectangular flat plate is bon...
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Designation: D2718 − 00 (Reapproved 2011)
Standard Test Methods for
Structural Panels in Planar Shear (Rolling Shear)
This standard is issued under the fixed designation D2718; 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.
1. Scope 2. Referenced Documents
1.1 These test methods determine the shear properties of
2.1 ASTM Standards:
structural panels associated with shear distortion of the planes
D2395 Test Methods for Density and Specific Gravity (Rela-
parallel to the edge planes of the panels. Both shear strength
tive Density) of Wood and Wood-Based Materials
and modulus of rigidity may be determined. Primarily, the tests
D4442 Test Methods for Direct Moisture Content Measure-
measure the planar shear (rolling shear) strength developed in
ment of Wood and Wood-Based Materials
the plane of the panel.
3. Significance and Use
1.2 Structural panels in use include plywood, waferboard,
oriented strand board, and composites of veneer and of
3.1 Planar shear (rolling shear) characteristics of structural
wood-based layers.
panels determined by these test methods are essential for the
rigorous design of various glued wood-panel structural
1.3 Two test methods are included:
components, such as box beams, folded plate roofs, and
1.3.1 Test Method A—Planar shear loaded by plates.
stressed skin panels. Planar shear also may govern the design
1.3.2 Test Method B—Planar shear induced by five-point
atlowspan-depthratiosencounteredinfloorssubjectedtohigh
bending.
concentrated loads, concrete forms at high pouring pressures,
1.3.3 The choice of method will be dictated by the purpose
and bulk storage structures.
of the test and equipment available.
1.3.4 Test Method A, Planar Shear Loaded by Plates—This
3.2 The modulus of rigidity determined fromTest MethodA
test method uses a rectangular panel section adhered between
is a composite of the entire specimen acting as a unit. For
steel plates with protruding knife edges to create load at the
plywood panels for which the ratio between the shear moduli
panel faces. This test method has been used to develop shear
oftheplieswithgrainorientedparallelandperpendiculartothe
properties of plywood and oriented strand board for the
shear forces is known, the rolling shear modulus of the
purpose of confirming design values.This test method does not
perpendicular plies can be calculated.
produce pure shear, but the specimen length is prescribed so
3.3 Veneer produced by slicing or rotary peeling may
that the secondary stresses have a minimum effect.The method
contain fine checks or separations parallel to the grain on the
determines shear strength and modulus of rigidity.
knife side of the veneer that are produced as the knife is forced
1.3.5 Test Method B, Planar Shear Induced by Five-Point
through the wood. These checks are termed “knife checks” to
Bending—Planar shear stress is induced on the panel while
distinguish them from occasional checks that may be formed
loaded in bending using two continuous spans. This test
on the opposite side of the veneer by forces at the compression
method determines planar shear strength consistent with panel
bar, and from checks caused by drying. Knife checks can have
applications under transverse loading. This test method is able
a significant effect on rolling shear properties in plywood
to determine shear strength at any moisture condition.
panels and may be of significance in other veneer containing
1.4 This standard does not purport to address all of the
panels.Test MethodArequires (when applicable) the testing of
safety concerns, if any, associated with its use. It is the
matching specimens having knife checks oriented both open
responsibility of the user of this standard to establish appro-
and closed wherever possible (see Fig. 1).
priate safety and health practices and determine the applica-
3.4 To control or define other variables influencing rolling
bility of regulatory limitations prior to use.
shear, these test methods require determination of moisture
This test method is under the jurisdiction of ASTM Committee D07 on Wood
and is the direct responsibility of Subcommittee D07.03 on Panel Products. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2011. Published November 2011. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1969. Last previous edition approved in 2000 as D2718 – 00 (2006). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D2718-00R11. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2718 − 00 (2011)
NOTE 1—The “V” block is supported on a seat that provides rotation
(a) Knife Checks Open
about the axis perpendicular to the knife edge only.
(b) Knife Checks Closed
Metric Equivalents
FIG. 1 Orientation of Knife Checks in Plywood
in. 6 18
mm 15 45
content, specific gravity, and elapsed time-to-failure. Condi-
FIG. 2 Planar (Rolling) Shear Test Using a Dial Gage for Measur-
tioning of test material in controlled atmospheres, determina-
ing Plate Slip
tion of depth of knife checks (when applicable), and determi-
nation of percent of wood and plywood glueline failure (when
applicable) are recommended. uniform material as well. However, smaller specimens of
uniform material may be used if these are not less than four
4. Control of Moisture Content
times the thickness in width nor twelve times the thickness in
4.1 The structural panel samples to be tested at specific length.
moisture contents or equilibrium relative humidities shall be
6.2 From each sample of panels containing veneer, two
conditioned to approximately constant weight in controlled
matching specimens shall be cut. Knife edges of loading plates
atmospheric conditions before gluing to plates. For approxi-
for one specimen of each matching pair shall be oriented
mating moisture conditions of structural panel used under dry
perpendicular to one of the primary panel directions or for
conditions a relative humidity of 65 6 2 % at a temperature of
plywood to cause opening of knife checks during test as shown
68 6 6°F (20 6 3°C) is recommended. Specimens shall be
in Fig. 1(a). Knife edges of plates loading the other specimen
tested without undue delay after the adhesive is cured. Testing
shall be positioned perpendicular to one of the primary panel
in similarly controlled atmospheres is recommended wherever
directions or for plywood to cause knife checks to close during
possible.
test as shown in Fig. 1(b). Proper plywood orientation may be
determined from check depth specimens described in 16.3.It
Test Method A—Planar Shear Loaded by Plates
may not be possible to test samples having two or more plies
stressed in rolling shear in both “open” and “closed” orienta-
5. Scope
tions if these plies are oriented in opposite directions causing a
5.1 The specimen having the form of a rectangular flat plate
“checks open” failure regardless of direction of loading.
is bonded between steel plates beveled at opposite ends of the
6.3 Specimen length and width shall be measured to the
specimen to provide knife edges for loading the plate at the
nearest 0.01 in. (0.25 mm) and thickness to the nearest 0.001
face bonded to the specimen. The knife edges project beyond
in. (0.025 mm). When applicable, the direction of knife checks
the ends of the specimen. This test method is conducted by
in plies having grain perpendicular to its length shall be
loading the knife edges in compression at a uniform rate while
determined and the specimens marked for position of knife
a suitable gage measures slip between the plates due to
edges. At the time specimens are cut matching samples for
specimen deformation. Shear strength is computed from maxi-
determination of moisture content and specific gravity in
mum load, and effective shear modulus for the specimen is
accordance with 16.1 and 16.2 shall be obtained. When
determined from a plot of load versus slip.
measurement of knife checks is included as discussed in 16.3,
6. Test Specimen
a sample for this measurement also may be cut at this time.
6.1 Specimen thickness shall be that of the material. Speci-
7. Loading
mensfrommaterialthatisexpectedtovarysignificantlywithin
the specimen due to growth or manufacturing features or from 7.1 Figs.1and2illustratethespecimenandsuitableloading
other causes shall be 6 in. (15 cm) wide by 18 in. (45 cm) long plates and blocks for loading the knife edges of the plates. The
or larger as shown in Fig. 2. This size is recommended for specimen shall be loaded by steel plates bonded to both faces
D2718 − 00 (2011)
of the specimen with an adhesive sufficiently rigid to preclude 7.3 Both epoxy and polyvinyl adhesives have been found
contributionofadhesivecreeptomeasureddeformation.Width satisfactory for bonding steel plates to specimens. Minimum
of plates shall be that of the specimen. One end of each plate required surface preparation of steel plates consists of removal
shall be provided with a knife edge projecting ⁄4 in. (6 mm) of residual adhesive. This can be accomplished most easily by
mild heating of the plate and any portion of the specimen
beyond the end of the specimen at one end and flush with the
surface glued to the specimen. The other end of the plate shall remaining from the previous test in an oven which weakens the
bond to the steel sufficiently to permit peeling the remaining
be square and flush with the end of the specimen. Knife edges
of the two plates shall be at opposite ends of the specimen and wood and adhesive from the plate. The residual adhesive may
be scraped off with a sharp-edged tool. Further degreasing and
shall be oriented to load the specimen in the desired direction
cleaning has frequently been found necessary in addition to the
in relation to the knife checks. Planar shear properties of
above to ensure adequate bond strength. Curing the adhesive at
structural panels should be determined in both directions.
a slightly elevated temperature has also been helpful.
Plates for specimens 18 in. (45 cm) long shall be 1 in. (2.5 cm)
thick. The thickness of plates for shorter specimens may be
8. Measurement of Deformation
reduced proportionately. Loading of at least one V-block shall
8.1 Slip between the steel plates during load application
provide for uniform load distribution along the knife edge by
shall be measured to at least the nearest 0.0001 in. (0.002 mm)
loading through a pivot having its axis perpendicular to the
at no less than twelve and preferably more equally spaced
knife edge and centered along it. Pivots permitting rotation
increments of load to proportional limit from which a load-
about an axis parallel to the knife edge or spherical seats free
deformation curve shall be plotted. Slip can be measured with
to pivot in this manner shall not be used as they create unstable
a dial gage as illustrated in Figs. 2 and 3 or with appropriate
loadingwhichmaycauseviolentejectionofthespecimenfrom
automatic measuring and recording equipment. Gage geometry
the machine and hazard to operating personnel. The V-blocks
and position on the specimen shall be such as to minimize any
shall be vertically positioned in the machine, one above the
effects of unsymmetrical loading or deformation.
other, causing the forces applied to the specimen to act parallel
to the axis of the machine. The specimen itself will be slightly
9. Calculation
inclined when placed in the machine. A means of holding the
9.1 Shear stress shall be calculated as follows:
plates in an upright position after the specimen has sheared
(2)
apart is desirable as a complete separation of the specimen
permits the plates to be thrown out of the machine with
where:
attendant hazard to the operator.
f = shear stress, psi (N/mm),
v
7.2 Loadshallbeappliedcontinuouslythroughoutthetestat P = maximum or proportional limit load (force), lbf (N),
W = specimen width, in. (mm), and
constant rate of cross-head motion to normally produce failure
L = specimen length, in. (mm).
in the range of 3 to 12 min elapsed time from beginning of
loading. For plywood, the approximate speed may be deter-
Maximum shear stress obtained from specimens having final
mined as follows:
failure of the bond between the plate and the specimen shall be
regarded as defective and shall be clearly indicated in the
N 5 0.0075 T 1R T (1)
~ !
'
( (
?
report of results.
where:
9.2 Effective modulus of rigidity for the specimen acting as
N = crosshead speed, in./min (cm/min),
a unit shall be calculated as follows:
∑T = total thickness of plies having grain parallel to
|
G 5 ~P/∆!@t/~L·W!# (3)
direction of shear force, in. (cm),
R = 8 (assumed ratio of shear modulus of parallel plies to
where:
shear modulus of perpendicular plies), and
G = apparent modulus of rigidity for the entire specimen,
∑T = total thickness of plies having grain perpendicular to
'
psi (N/mm),
the direction of shear force, in. (cm).
t = specimen thickness, in. (mm),
P/∆ = slope of the force-deformation curve below propor-
7.2.1 Elapsed time from beginning of load application to
tional limit load, lbf/in. (N/mm), and other notation is
failure of each specimen shall be measured and recorded to the
as indicated in 9.1.
nearest half minute. Machine speeds calculated by the above
formula will normally produce failure in the range of 3 to 12 For plywood, modulus of rigidity of the cross plies may be
min elapsed time from the beginning of loading. Should calculated from that given above if the ratio of moduli of
elapsed time to failure fall greatly outside this range, machine
rigidity and thickness of the parallel and perpendicular plies is
speed should be modified to obtain times within this range. known.
D2718 − 00 (2011)
FIG. 3 Planar (Rolling) Shear Specimen Ready for Testing
3,4
available. Research on the test method’s usefulness for determining
Test Method B—Planar Shear Induced by Five-Point
elastic constants is also available.
Bending
10. Scope
11. Test Specimen
10.1 Specimens are tested in a two-span continuous beam
11.1 The test specimen shall be rectangular in cross-section.
support configuration with line loads applied at midspan of
The depth of the specimen shall be the thickness of the
each span as shown in Fig. 4. Induced shear stresses are
material, and the width shall be at least 4.5 in. (115 mm) and
consist
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