ISO 8375:2017

INTERNATIONAL ISO
STANDARD 8375
Third edition
2017-06
Timber structures — Glued
laminated timber — Test methods
for determination of physical and
mechanical properties
Structures en bois — Bois lamellé-collé — Méthodes d’essai pour la
détermination de certaines propriétés physiques et mécaniques
Reference number
ISO 8375:2017(E)
©
ISO 2017

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ISO 8375:2017(E)

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ISO 8375:2017(E)

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and suffixes . 2
4.1 Symbols . 2
4.2 Suffixes . 3
5 Determination of dimensions of test specimens . 3
6 Determination of moisture content of test specimens . 3
7 Determination of density of test specimens . 4
8 Conditioning of test specimens . 4
9 Determination of local (shear-free) modulus of elasticity of the beam in bending .4
9.1 Test specimen . 4
9.2 Procedure . 4
9.3 Expression of results . 5
10 Determination of global modulus of elasticity of the beam in bending .6
10.1 Test specimen . 6
10.2 Procedure . 6
10.3 Expression of results . 7
11 Determination of shear modulus of the beam — Variable span method .7
11.1 General . 7
11.2 Test piece . 8
11.3 Procedure . 8
11.4 Expression of results . 9
11.4.1 Determination of K and K .
1 2 9
11.4.2 Shear modulus . 9
12 Determination of bending strength of the beam.10
12.1 Test specimen .10
12.2 Procedure .10
12.3 Expression of results .11
13 Determination of the modulus of elasticity in tension parallel to the grain of the
glued laminated timber .11
13.1 General .11
13.2 Test specimen .11
13.3 Procedure .11
13.4 Expression of results .12
14 Determination of the parallel to the grain tension strength of the glued
laminated timber .12
14.1 Test specimen .12
14.2 Procedure .12
14.3 Expression of results .12
15 Determination of the modulus of elasticity in compression parallel to the grain of
the glued laminated timber.13
15.1 General .13
15.2 Test specimen .13
15.3 Procedure .13
15.4 Expression of results .13
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ISO 8375:2017(E)

16 Determination of the parallel to grain compression strength of the glued
laminated timber .14
16.1 Test specimen .14
16.2 Procedure .14
16.3 Expression of results .14
17 Determination of the modulus of elasticity in compression and tension
perpendicular to the grain of the glued laminated timber .14
17.1 Requirements for test specimens .14
17.2 Procedure .15
17.3 Expression of results .15
17.3.1 Compression perpendicular to the grain .15
17.3.2 Tension perpendicular to the grain .16
18 Determination of tension and compression strengths perpendicular to the grain of
the glued laminated timber.17
18.1 Requirements for test specimens .17
18.1.1 Fabrication .17
18.1.2 Surface preparation .17
18.2 Procedure .17
18.3 Expression of results .19
18.3.1 Compression perpendicular to the grain .19
18.3.2 Tension perpendicular to the grain .20
19 Determination of shear strength parallel to the grain — Small specimen test .20
19.1 Requirements for test specimens .20
19.1.1 Fabrication .20
19.1.2 Surface preparation .20
19.2 Procedure .21
19.3 Expression of results .22
20 Determination of shear strength parallel to the grain — Full size beam test .23
20.1 Specimen .23
20.2 Procedure .23
20.3 Expression of result .24
21 Test report .25
21.1 General .25
21.2 Test specimen .25
21.3 Test method .25
21.4 Test results.25
Bibliography .26
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ISO 8375:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 165, Timber structures.
This third edition cancels and replaces the second edition (ISO 8375:2009), which has been technically
revised.
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INTERNATIONAL STANDARD ISO 8375:2017(E)
Timber structures — Glued laminated timber — Test
methods for determination of physical and mechanical
properties
1 Scope
This document specifies test methods suitable for determining the following characteristic values of
glued laminated timber: modulus of elasticity in bending; shear modulus; bending strength; modulus of
elasticity in tension parallel to the grain; tension strength parallel to the grain; modulus of elasticity in
compression parallel to the grain; compression strength parallel to the grain; modulus of elasticity in
tension perpendicular to the grain; tension strength perpendicular to the grain; modulus of elasticity
in compression perpendicular to the grain; compression strength perpendicular to the grain and shear
strength.
In addition, the determination of dimensions, moisture content and density are specified.
This document is applicable to rectangular shapes of glued laminated timber.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
density
characteristic mean density obtained at a 75 % confidence limit with mass and volume corresponding
to equilibrium moisture content at a temperature of 20 °C and a relative humidity of 65 %
Note 1 to entry: ISO 12122-1 and ISO 12122-3 provide guidelines for statistical processing of data to determine
characteristic values such as density.
3.2
strength
characteristic lower 5-percentile value at a 75 % confidence limit obtained from the results of tests
using test specimens at an equilibrium moisture content resulting from a temperature of 20 °C and
a relative humidity of 65 % or the strength value at the observed moisture content when full size
members are tested
Note 1 to entry: ISO 12122-1 and ISO 12122-3 provide guidelines for statistical processing of data to determine
characteristic values such as strength.
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ISO 8375:2017(E)

3.3
elasticity
characteristic mean stiffness at a 75 % confidence limit obtained from the results of tests using test
specimens at an equilibrium moisture content resulting from a temperature of 20 °C and a relative
humidity of 65 %
Note 1 to entry: ISO 12122-1 and ISO 12122-3 provide guidelines for statistical processing of data to determine
characteristic values such as elasticity.
3.4
specimen
item to be tested for the determination of all characteristic values
Note 1 to entry: The minimum number of test specimens required for the determination of all characteristic
values is provided in ISO 12122-1 and ISO 12122-3, unless otherwise noted for the specific test involved.
3.5
population
specimens (3.4) used to determine characteristic values
Note 1 to entry: Specimens should be reflective of the population they are intended to represent.
4 Symbols and suffixes
4.1 Symbols
A cross-sectional area, in square millimetres
a distance between a loading position and the nearest support in a bending test, in mil-
limetres
b width of cross section in a bending test, or the smaller dimension of the cross section, in
millimetres
E modulus of elasticity in compression parallel to the grain, in megapascals
c,0
E modulus of elasticity in compression perpendicular to the grain, in megapascals
c,90
E global modulus of elasticity in bending, in megapascals
m,g
E apparent modulus of elasticity in bending, in megapascals
m,app
E modulus of elasticity in tension parallel to the grain, in megapascals
t,0
E modulus of elasticity in tension perpendicular to the grain, in megapascals
t,90
F load, in newtons
F maximum compressive load perpendicular to the grain, in Newtons
c,90,max
F estimated maximum compressive load perpendicular to the grain, in Newtons
c,90,max,est
F maximum load, in Newtons
max
F estimated maximum load, in Newtons
max,est
F maximum tensile load perpendicular to the grain, in Newtons
t,90,max
f compressive strength parallel to the grain, in megapascals
c,0
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ISO 8375:2017(E)

f compressive strength perpendicular to the grain, in megapascals
c,90
f bending strength, in megapascals
m
f tensile strength parallel to the grain, in megapascals
t,0
f tensile strength perpendicular to the grain, in megapascals
t,90
f shear strength parallel to the grain, in megapascals
v
G shear modulus, in megapascals
h depth of cross section in a bending test, or the larger dimension of the cross section, or
the test specimen height in perpendicular to grain tests, in millimetres
h gauge length, in millimetres
0
I second moment of area, in millimetres to the fourth power
K, k coefficients
k coefficient for shear modulus
G
l span in bending, or length of test specimen between the testing machine grips in com-
pression and tension, in millimetres
S section modulus, in millimetres to the third power
w deformation, in millimetres
4.2 Suffixes
1, 2 loads or deformations at particular points of a test, referred to as necessary in the text
5 Determination of dimensions of test specimens
The dimensions of the test specimen shall be measured to an accuracy of 1 %. The dimension measuring
devices shall be such as to permit measuring dimensions in millimetres to three significant figures. All
measurements shall be made when the test specimens are conditioned as specified in Clause 8. If the
width or thickness varies within a test specimen, these dimensions should be recorded as the average
of three separate measurements taken at different positions on the length of each specimen.
Where possible, the measurements should not be taken closer than 150 mm to the ends of the specimen.
6 Determination of moisture content of test specimens
The moisture content of the test specimen shall be determined on a section taken from the test
specimen.
In strength tests for bending, shear, tension parallel and perpendicular to grain and compression
parallel and perpendicular to grain, the moisture content of the test specimen shall be determined as
soon as practical after testing or the specimen shall be sealed to prevent any further moisture change
until testing can be initiated. The section shall be cut as close as possible to the fracture.
As an alternative, the provisions of ISO 3130 or ASTM D4442 may be used for determining moisture
content.
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ISO 8375:2017(E)

7 Determination of density of test specimens
If a density value is needed, the density shall be determined on a portion of the cross section or the
entire cross section taken from the test specimen near the fracture area.
In strength tests such as bending and parallel to grain, the density of the test specimen shall be
determined after the testing and the section shall be cut as close as possible to the fracture.
For perpendicular to grain test specimens, the density of the test specimens shall be determined prior
to test from the measurements of mass and volume of the whole test specimen.
As an alternative, the provisions of ISO 3131 or ASTM D2395 are acceptable for determining density.
8 Conditioning of test specimens
The tests shall be carried out on specimens that are conditioned at the standard environment of
(20 ± 2) °C and (65 ± 5) % relative humidity. A test piece is conditioned when it attains constant mass.
Constant mass is considered to be attained when the results of two successive weightings, carried out
at an interval of 6 h, do not differ by more than 0,1 % of the mass of the test specimen.
The provisions of ASTM D4933 are also acceptable to establish moisture conditioning.
Where the timber to be tested cannot be readily conditioned to the above standard environment, that
fact shall be reported and the moisture content of the test specimen shall be reported with the test
results.
For small specimens, unless otherwise protected, test specimens shall not be removed from the
conditioning environment more than 1 h before testing.
NOTE Test specimens can be stored in the test area for up to 24 h provided they are closely stacked and
wrapped in vapour-tight wrapping.
9 Determination of local (shear-free) modulus of elasticity of the beam in bending
9.1 Test specimen
The test specimen shall have a minimum length to permit testing with a span of approximately 18 times
the depth of the section. The test span shall be reported.
9.2 Procedure
The test specimen shall be symmetrically loaded in bending at two points over a span of 18 (± 3) times
the depth as shown in Figure 1. The span between load heads shall be six times the specimen depth. All
spans and distances shall be noted and measured to the nearest millimetre.
NOTE 1 The intent of this document is to test with a span equal to 18 times the depth. Tolerances are provided
to enable testing of a broader range of specimens.
The test specimen shall be simply supported.
NOTE 2 Small steel plates of length not greater than one-half of the depth of the test specimen can be inserted
between the specimen and the loading heads or supports to minimize local indentation.
Lateral restraint shall be provided as necessary to prevent buckling. This restraint shall permit the
specimen to deflect without significant frictional resistance.
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ISO 8375:2017(E)

Load shall be applied at a constant rate and the test should be completed within approximately 300 s
but not less than 180 s.
NOTE 3 Ideally, the load application rate is determined from the results of preliminary tests. The objective is
that the average time to reach F is 300 s.
max
The maximum load applied shall not exceed the proportional limit load or cause damage to the piece.
Figure 1 — Test arrangement for measuring local modulus of elasticity in bending
The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load
applied to the test specimen or, for loads less than 10 % of the applied maximum load, with an accuracy
of 0,1 % of the maximum applied load.
The deformation, w, shall be measured at the neutral axis, at the centre of a central gauge length of five
times the depth of the section as shown in Figure 1.
The deformation measuring devices and recording system shall be such as to permit measuring
deflections to the nearest millimetre.
NOTE 4 ASTM D198 provides a descr
...