ISO 13910:2014
(Main)Timber structures — Strength graded timber — Test methods for structural properties
Timber structures — Strength graded timber — Test methods for structural properties
ISO 13910:2014 specifies test procedures for full-size sawn timber that has been strength-graded, for the derivation of design properties in codes dealing with structural engineering design. It is applicable to sawn timber of rectangular cross-section subjected to a short-duration load.
Structure en bois — Bois classé selon la résistance — Méthodes d'essai des propriétés structurelles
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INTERNATIONAL ISO
STANDARD 13910
Second edition
2014-05-01
Timber structures — Strength graded
timber — Test methods for structural
properties
Structure en bois — Bois classé selon la résistance — Méthodes
d’essai des propriétés structurelles
Reference number
ISO 13910:2014(E)
©
ISO 2014
---------------------- Page: 1 ----------------------
ISO 13910:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 13910:2014(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Symbols and abbreviated terms . 2
3.1 General notation . 2
3.2 Subscripts . 3
4 Test specimens. 3
5 Test conditions . 3
6 Test configurations . 3
6.1 Density . 3
6.2 Bending strength and stiffness . 4
6.3 Tension strength parallel to the grain . 5
6.4 Compression strength parallel to the grain . . 6
6.5 Shear strength parallel to the grain . 7
6.6 Tension strength perpendicular to the grain . 9
6.7 Compression strength and stiffness perpendicular to the grain .11
6.8 Torsional shear modulus .13
7 Adjustment for non-reference test conditions .14
8 Test report .15
Annex A (informative) Adjustment factors for non-reference condition .16
Bibliography .17
© ISO 2014 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 13910:2014(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. 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. 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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 165 Timber Structures.
This second edition cancels and replaces the first edition (ISO 13910:2005), which has been technically
revised.
iv © ISO 2014 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 13910:2014(E)
Introduction
This International Standard provides requirements for testing of structural properties for a specific
grade and size of sawn timber. In accordance with the requirements of performance-based International
Standards, it is concerned with the measurement of properties similar to those that occur under service
conditions and are intended for deriving engineering properties in structural design codes. Hence, terms
such as “bending strength”, “shear strength”, “bearing strength”, etc. relate to the loading configuration
used and to the targeted mode of failure.
It is not the intent to imply that every property of every grade and size of timber used in building
construction needs to be assessed according to this International Standard. The requirements for any
assessment typically are specified in building regulations, quality manuals or other material standards
and specifications.
This document is an internationally-agreed reference standard for measurement of structural properties
of strength-graded timber. Other standards related to the measurement of structural properties may
be deemed to comply with this International Standard, provided that the adjustments necessary to
establish equivalency between this and other standards are applied appropriately
© ISO 2014 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 13910:2014(E)
Timber structures — Strength graded timber — Test
methods for structural properties
1 Scope
This International Standard specifies test procedures for full-size sawn timber that has been strength-
graded, for the derivation of design properties in codes dealing with structural engineering design. It is
applicable to sawn timber of rectangular cross-section subjected to a short-duration load.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
grade
population of timber with defined design properties in a design standard
2.2
piece of timber
timber of rectangular cross-section manufactured for construction purposes of a specific grade
2.3
test specimen
length of timber, cut from a piece, for purposes of testing to evaluate a timber property
© ISO 2014 – All rights reserved 1
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ISO 13910:2014(E)
3 Symbols and abbreviated terms
3.1 General notation
a distance between a load point and nearest support in a bending test set-up, expressed in mm
b thickness (smaller dimension of a cross section) of a rectangular piece or specimen of tim-
ber, expressed in mm
E modulus of elasticity parallel to direction of grain, expressed in MPa
F applied load, expressed in N
f strength, expressed in MPa
G shear modulus of rigidity, expressed in MPa
h width (larger dimension of a cross section) of a rectangular piece or specimen of timber,
expressed in mm
K stiffness, expressed in N per mm deformation
L length along a piece or specimen of timber, expressed in mm
L length of test specimen subjected to torsion forces, expressed in mm
T
l length cut from a specimen, expressed in mm
h
l lever arm of applied torsion load, expressed in mm
t
e displacement of beam, expressed in mm
m mass of specimen, expressed in kg
SH volumetric shrinkage of wood from green fibre saturation point (FSP) to oven-dry condition
v
w ratio of mass of water to mass of oven-dry wood, equivalent to moisture content
w moisture content at fibre saturation point
FSP
x data value
i
θ rotational deformation in a torsion test, in radians
3
ρ density, expressed in kg/m
3
ρ density, expressed in kg/m , at 12% moisture content
12
3
ρ density, expressed in kg/m , at time of test
test
2 © ISO 2014 – All rights reserved
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ISO 13910:2014(E)
3.2 Subscripts
0.1h value at deformation of 0.1h
0 property in a direction of 0° to the grain
90 property in a direction of 90° to the grain
c compression
m bending
t tension
ult value at failure
v shear
4 Test specimens
All test specimens are of full-size cross section. The length required for a test specimen shall be related
to the specific test (see Clause 6).
Unless otherwise stated, test specimens shall be selected from random locations within a piece of
timber. Specimens cut from pre-defined locations (centre of a piece of timber, a randomly selected end
within a piece or clear sections, etc.) may be deemed to comply with this requirement provided this does
not produce any bias in the measured properties.
Each test specimen for a given size, grade or property shall be cut from a different piece of timber and
more than one type of test specimen may be cut from each piece.
5 Test conditions
Unless otherwise specified in the description of the reference population, the reference moisture content
at the time of testing shall be consistent with conditioning at a temperature of 20°C (±2°C) and 65 %
(±5 %) relative humidity. Other test procedures and conditioning criteria may be used provided they
are more conservative; otherwise, an equivalency in performance for these alternative procedures and
conditions shall be established. The rate of loading shall be selected that targets average time-to-failure
in 1 min to 5 min.
NOTE The intent here is not to reject data for weak pieces that fail in a short time.
At the time of testing, the moisture content of the timber, the temperature of the timber, and the time to
failure shall be recorded.
6 Test configurations
6.1 Density
The specimens for the measurement of density shall be free of knots and comprise the full cross-section
of the piece of timber. The length of the test specimen shall be a minimum of 50 mm. The mass, m, and
© ISO 2014 – All rights reserved 3
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ISO 13910:2014(E)
moisture content, w, are measured for each test specimen. The density at the time of test, ρ , shall be
test
calculated from
9
m×10
ρ = (1)
test
Lbh
The density at 12 % moisture content, ρ , shall be calculated from
12
ρρ=−[,10 50(,w− 12)] (2)
12 test
where w is the moisture content at the time of test as determined by the oven-dry method.
Alternatively, it may be sufficiently accurate to measure moisture content by means of a moisture
meter, provided that the meter is calibrated against moisture content measurements determined by the
oven dry method. Where such moisture meter measurements are made, they shall be made at several
locations along each specimen.
NOTE If specific gravity (e.g. based on oven-dry mass and oven-dry volume, SG ) is desired, it can be
OD
estimated from wood density at test, ρ , moisture content, w, fibre saturation point, w , and wood volumetric
test FSP
shrinkage, SH , as follows:
v
(/1+wSHw )ρ
vFSP test
SG =
OD
1000()1+w
6.2 Bending strength and stiffness
The bending strength and stiffness test configuration shall be as shown in Figure 1. The beam specimen
shall be loaded at two points, equally spaced between the end supports, with each load equal to F/2.
The distance between load points shall be 6 h and the distance between a load point and the nearest
support, a, shall be 4,5 h to 7 h. The tension edge of the beam shall be chosen randomly. If the beam has a
slenderness where there could be a tendency for the compression edge to buckle during loading, lateral
restraints may be provided to the compression edge. Such restraints shall not resist any movement in the
direction of the loading. Bearing blocks at loading and support points (see Figure 1), shall be of sufficient
thickness and extend entirely across the beam thickness to eliminate high-stress concentrations at
places of contact between beam and bearing blocks. Load shall be applied to the blocks in such a manner
that the blocks may rotate about an axis perpendicular to the span. The slider bearing plate in Figure 1
shall allow rotation and horizontal movement whereas the bearing plate shall allow only rotation.
F/2
F/2
1
1 b
C
A
B
h
e
2
a
a
1
L
Key
1 slider bearing plate
2 bearing plate (rocker)
Figure 1 — Test set-up for measuring bending strength and stiffness
4 © ISO 2014 – All rights reserved
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ISO 13910:2014(E)
Modulus of elasticity, E, shall be calculated from measurement of e, the centre-point deflection of the
centre-line of the beam relative to the position of the centre-line at the ends of the beam, i.e. the deflection
of point B relative to points A and C as shown in Figure 1.
NOTE Centre-point deflection measured by referencing the displacement transducer against the top or
bottom edge of the beam or by using loading head movement usually contains unintended displacement component
due to the indentation of the wood material at the support and loading points, etc. Deflection measured by such
methods can be used for calculation of E provided it can be shown that it leads to more conservative result.
The applied load, F, shall be increased until the maximum load is reached.
To evaluate the modulus of elasticity in bending, E , the incremental deflection ∆e for an incremental
m
load ∆F shall be selected from the linear elastic part of the load-deformation graph. E is calculated
m
from:
a ΔF
22
E = ()34La− (3)
m
3
Δe
4bh
The range of 10 % to 40 % of the maximum load shall be used to determine ∆F/∆e. The deflection e
may be evaluated by the measurement of the movement of points other than those described above,
provided that an acceptable equivalency for these procedures is established, or it can be shown that the
alternative procedures produce conservative results.
NOTE The test set-up will lead to the determination of apparent modulus of elasticity. Shear-corrected
modulus of elasticity can be estimated by adjusting the measured deflection, Δs, using the following formula
assuming shear modulus is known (For structural timber, G can be assumed to be E/16.), and substituting Δe into
Formula (3):
3ΔFa
ΔΔes=−1
5ΔbhG s
The bending strength, f , shall be calculated from
m
3Fa
ult
f = (4)
m
2
bh
where F is the value of the applied load at failure.
ult
6.3 Tension strength parallel to the grain
NOTE The gauge length used is typically longer than the stated minimum to increase the likelihood that the
critical strength-reducing defect is captured within the gauge length.
1
1
b
F
F
h
Gauge length
Key
1 grip
Figure 2 — Test setup for measuring tension strength parallel to the grain
© ISO 2014 – All rights reserved 5
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ISO 13910:2014(E)
The tension strength f shall be calculated from
t,0
F
ult
f = (5)
t,0
bh
where F is the value of the applied load at failure.
ult
6.4 Compression strength parallel to the grain
The compression strength parallel to the grain test configuration shall be as shown in Figure 3. The test
specimen shall be the full length of the piece of timber. It shall be compressed axially by a load F until
failure occurs. The specimen should be restrained against lateral buckling with the spacing of the lateral
restraints not greater than 5h for buckling about the major axis and 5b for buckling about the minor
axis. The lateral restraint shall not provide any resistance in the direction of the loading.
< 5h
b
1
F
F
h
< 5b
1
Key
1 lateral restraint
Figure 3 — Test setup for measuring compression strength parallel to the grain using the full
length test specimen
The compression strength f shall be calculated from
c,0
F
ult
f = (6)
c,0
bh
where F is the value of the applied load at failure.
ult
An alternative test procedure using short compression specimen is permitted to be used provided that
the relationship between the full-length and short-length test st
...
DRAFT INTERNATIONAL STANDARD ISO/DIS 13910
ISO/TC 165 Secretariat: CFI
Voting begins on Voting terminates on
2013-02-11 2013-05-11
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ ORGANISATION INTERNATIONALE DE NORMALISATION
Timber structures — Strength graded timber — Test methods
for structural properties
Structure en bois — Bois classé selon la résistance — Méthodes d'essai des propriétés structurelles
[Revision of first edition (ISO 13910:2005)]
ICS 91.080.20
To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
publication stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME
STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2013
---------------------- Page: 1 ----------------------
ISO/DIS 13910
Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted
under the applicable laws of the user’s country, neither this ISO draft nor any extract from it may be
reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic,
photocopying, recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2013 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 13910
Contents Page
Foreword .iv
Introduction v
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Symbols and abbreviated terms .1
4.1 General notation .1
4.2 Subscripts .2
5 Test specimens.2
6 Test conditions .2
7 Test configurations .2
7.1 Density.2
7.2 Bending strength and stiffness.3
7.3 Tension strength parallel to the grain .5
7.4 Compression strength parallel to the grain .5
7.5 Shear strength parallel to the grain .6
7.6 Tension strength perpendicular to the grain .8
7.7 Compression strength and stiffness perpendicular to the grain.11
7.8 Torsional shear modulus .13
8 Adjustment for non-standard test conditions.14
9 Test report .15
Bibliography.16
© ISO 2012 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 13910
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.
International Standards are drafted in accordance with the rules given in the
ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member
bodies casting a vote.
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.
ISO/DIS 13910 was prepared by Technical Committee ISO/TC 165 Timber Structures
This second edition cancels and replaces the first edition (ISO 13910 2005)
iv © ISO 2012 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/DIS 13910
Introduction
This International Standard provides requirements for testing of structural properties for a
specific grade and size of sawn timber. In accordance with the requirements of performance-
based International Standards, it is concerned with the measurement of properties similar to
those that occur under service conditions and are intended for deriving engineering properties
in structural design codes. Hence, terms such as “bending strength”, “shear strength”, “bearing
strength”, etc. relate to the loading configuration used and to the targeted mode of failure.
It is not the intent to imply that every property of every grade and size of timber used in building
construction needs to be assessed according to this International Standard. The requirements
for any assessment typically are specified in building regulations, quality manuals or other
material standards and specifications.
This document is an internationally-agreed reference standard for measurement of structural
properties of strength-graded timber. Other standards related to the measurement of structural
properties may be deemed to comply with this International Standard, provided that the
adjustments necessary to establish equivalency between this and other standards are applied
appropriately
© ISO 2012 – All rights reserved v
---------------------- Page: 5 ----------------------
DIS ISO/DIS 13910
Timber structures – Strength graded timber – Test methods for
structural properties
1 Scope
This International Standard specifies test procedures for full-size sawn timber that has been strength-graded,
for the derivation of design properties in codes dealing with structural engineering design. It is applicable to
sawn timber of rectangular cross-section subjected to a short-duration load.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ASTM D198 Standard test methods of static tests of lumber in structural sizes
AS/NZS 4063 Timber - Stress-graded - In-grade strength and stiffness evaluation
EN 408 Timber structures. Structural timber and glued laminated timber. Determination of some
physical and mechanical properties
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
Grade population of timber with defined design properties in a design standard
Piece of timber timber of rectangular cross-section manufactured for construction purposes of a specific
grade
Test specimen length of timber, cut from a piece, for purposes of testing to evaluate a timber property
4 Symbols and abbreviated terms
4.1 General notation
a distance between a load point and nearest support in a bending test set-up, expressed in millimetres
b thickness (smaller dimension of a cross section) of a rectangular piece or specimen of timber, expressed
in millimetres
E modulus of elasticity parallel to direction of grain, expressed in Newtons per square millimetre
F applied load, expressed in Newtons
f strength, expressed in Newtons per square millimetre
G shear modulus of rigidity, expressed in Newtons per square millimetre
h width (larger dimension of a cross section) of a rectangular piece or specimen of timber, expressed in
millimetres
K stiffness, expressed in Newtons per square millimetre per millimetre deformation
L length along a piece or specimen of timber, expressed in millimetres
L length test specimen subjected to torsion forces, expressed in millimetres
T
l length cut from a specimen, expressed in millimetres
h
© ISO 2012 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/DIS 13910
l lever arm of applied torsion load, expressed in millimetres
t
e displacement of beam, expressed in millimetres
m mass of specimen, expressed in kilograms
SH volumetric shrinkage of wood from green fibre saturation point (FSP) to oven-dry condition
v
w ratio of mass of water to mass of oven-dry wood, equivalent to moisture content
w moisture content at fibre saturation point
FSP
x data value
i
θ rotational deformation in a torsion test, in radians
ρ density, expressed in kilograms per cubic metre,
ρ density, expressed in kilograms per cubic metre, at 12% moisture content
12
ρ density, expressed in kilograms per cubic metre, at time of test
test
4.2 Subscripts
0.1h value at deformation of 0.1h
0 property in a direction 0° to the grain
90 property in a direction of 90° to the grain
c compression
m bending
t tension
ult value at failure
v shear
5 Test specimens
All test specimens are of full-size cross section. The length required for a test specimen shall be related to the
specific test (see Clause 7).
Unless otherwise stated, test specimens shall be selected from random locations within a piece of timber.
Specimens cut from pre-defined locations (centre of a piece of timber, a randomly selected end within a piece
or clear sections, etc.) may be deemed to comply with this requirement provided this does not produce any
bias in the measured properties.
Each test specimen for a given size, grade or property shall be cut from a different piece of timber and more
than one type of test specimen may be cut from each piece.
6 Test conditions
Unless otherwise specified in the description of the reference population, the reference moisture content at the
time of testing shall be consistent with conditioning at a temperature of 20°C (±2°C) and 65 % (±5%) relative
humidity. Other test procedures and conditioning criteria may be used provided they are more conservative;
otherwise, an equivalency in performance for these alternative procedures and conditions shall be established.
The rate of loading shall be selected that targets average time-to-failure in 1 to 5 minutes. (Note: The intent
here is not to reject data for weak pieces that fail in a short time.).
At the time of testing, the moisture content of the timber, the temperature of the timber, and the time to failure
shall be recorded.
7 Test configurations
7.1 Density
The specimens for the measurement of density shall be free of knots and comprise the full cross-section of
2 © ISO 2012 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DIS 13910
the piece of timber. The length of the test specimen shall be not less than h. The mass, m, and moisture
content, w, are measured for each test specimen. The density at the time of test, " , shall be calculated from
test
(1)
The density at 12% moisture content, " , shall be calculated from
12
(2)
where w is the moisture content at the time of test as determined by the oven-dry method.
Alternatively, it may be sufficiently accurate to measure moisture content by means of a moisture meter,
provided that the meter is calibrated against moisture content measurements determined by the oven dry
method. Where such moisture meter measurements are made, they shall be made at several locations along
each specimen.
NOTE: If specific gravity (e.g. based on oven-dry mass and oven-dry volume, SG ) is desired, it can be
OD
estimated from wood density at test (" ), moisture content (w), fibre saturation point w , and wood
test FSP
volumetric shrinkage (SH ) as follows:
v
7.2 Bending strength and stiffness
The bending strength and stiffness test configuration shall be as shown in Figure 1. The beam specimen shall
be loaded at two points, equally spaced between the end supports, with each load equal to F/2. The distance
between load points shall be 6h and the distance between a load point and the nearest support, a, shall be
4.5h to 7h. The tension edge of the beam shall be chosen randomly. If the beam has a slenderness where
there could be a tendency for the compression edge to buckle during loading, lateral restraints may be
provided to the compression edge. Such restraints shall not resist any movement in the direction of the
loading. Bearing blocks at loading and support points (Fig. 1), shall be of sufficient thickness and extend
entirely across the beam thickness to eliminate high-stress concentrations at places of contact between beam
and bearing blocks. Load shall be applied to the blocks in such a manner that the blocks may rotate about an
axis perpendicular to the span. The slider bearing plate in Figure 1 shall allow rotation and horizontal
movement whereas the bearing plate shall allow only rotation.
© ISO 2012 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO/DIS 13910
"#$%&'!(!)!*'+,!+',)%-!./&!0'1+%$!3'24#2$!+,&'2$,5!124!+,#.2'++!
Modulus of elasticity, E, shall be calculated from measurement of e, the centre-point deflection of the centre-
line of the beam relative to the position of the centre-line at the ends of the beam, i.e. the deflection of point B
relative to points A and C as shown in Figure 1.
The applied load, F, shall be increased until the maximum load is reached.
To evaluate the modulus of elasticity in bending, E , the incremental deflection #e for an incremental load #F
m
shall be selected from the linear elastic part of the load-deformation graph. E is calculated from
m
(3)
The range of 10 % to 40 % of the maximum load shall be used to determine #F/#e. The deflection e may be
evaluated by the measurement of the movement of points other than those described above, provided that an
acceptable equivalency for these procedures is established, or it can be shown that the alternative procedures
produce conservative results.
NOTE : The test set-up will lead to the determination of apparent modulus of elasticity. Shear-corrected
modulus of elasticity can be estimated by adjusting the measured deflection, $s, using the following formula
assuming shear modulus is known (For structural timber, G can be assumed to be E/16.), and substituting $e
into equation (3):
The bending strength f shall be calculated from
m
(4)
where F is the value of the applied load at failure.
ult
4 © ISO 2012 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/DIS 13910
7.3 Tension strength parallel to the grain
The tension strength parallel to the grain test configuration shall be as shown in Figure 2. The specimen shall
have a length between grips (gauge length) equal to at least 9h when tested in self-aligning grips. However,
when tested without self-aligning grips, it is recommended that the length between grips be at least 20h. The
specimen shall be loaded to failure.
NOTE: The gauge length used is typically longer than the stated minimum to increase the likelihood that the
critical strength-reducing defect is captured within the gauge length.
"#$%&'!6!)!*'+,!+',%-!./&!0'1+%$!,'2+#/2!+,&'2$,5!-1&177'7!,/!,5'!$&1#2!
The tension strength f shall be calculated from
t,0
(5)
where F is the value of the applied load at failure.
ult
7.4 Compression strength parallel to the grain
The compression strength parallel to the grain test configuration shall be as shown in Figure 3. The test
specimen shall be the full length of the piece of timber. It shall be compressed axially by a load F until failure
occurs. The specimen should be restrained against lateral buckling with the spacing of the lateral restraints
not greater than 5h for buckling about the major axis and 5b for buckling about the minor axis. The lateral
restraint shall not provide any resistance
...
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