ISO 13910:2005

Structural timber — Characteristic values of strength-graded timber — Sampling, full-size testing and evaluation

ISO 13910:2005 specifies sampling, full-size testing and evaluation procedures for the assessment of the characteristic values of the structural properties of sawn timber for use in codes dealing with structural engineering design. It provides methods for establishing equivalency with other standards for the testing and evaluation of characteristic properties of structural timber. It is applicable to sawn timber of rectangular cross-section subjected to a short-duration (approx. 1 min) load. Its evaluation procedure is not intended to be used for quality-control purposes or for acceptance of parcels of timber.

Bois de structure — Valeurs caractéristiques du bois classé selon la résistance — Échantillonnage, essais en grandeur nature et évaluation

General Information

• Status: Withdrawn
• Publication Date: 10-Feb-2005
• Withdrawal Date: 10-Feb-2005
• ICS: 91.080.20 - Timber structures
• Technical Committee: ISO/TC 165 - Timber structures
• Drafting Committee: ISO/TC 165 - Timber structures
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 06-May-2014

Relations

• Revised: ISO 13910:2014 - Timber structures — Strength graded timber — Test methods for structural properties
• Effective Date: 28-Feb-2009

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13910
First edition
2005-02-15

Structural timber — Characteristic values
of strength-graded timber — Sampling,
full-size testing and evaluation
Bois de structure — Valeurs caractéristiques du bois classé selon la
résistance — Échantillonnage, essais en grandeur nature et évaluation




Reference number
ISO 13910:2005(E)
©
ISO 2005

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ISO 13910:2005(E)
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ii © ISO 2005 – All rights reserved

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ISO 13910:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviated terms. 2
4.1 General notation. 2
4.2 Subscripts. 3
5 Sampling . 4
6 Test specimens . 4
7 Test conditions. 4
8 Test configurations. 4
8.1 Density . 4
8.2 Bending strength and stiffness . 5
8.3 Tension strength parallel to the grain. 6
8.4 Compression strength parallel to the grain . 7
8.5 Shear strength parallel to the grain . 7
8.6 Tension strength perpendicular to the grain .8
8.7 Compression strength and stiffness perpendicular to the grain. 9
8.8 Torsional rigidity . 11
9 Evaluation of characteristic values of properties tested. 12
9.1 Adjustment for non-standard test conditions. 12
9.2 Statistical processing. 13
10 Design strength properties . 15
11 Test report. 15
Annex A (informative) Equivalence with other standards. 16
Annex B (informative) Double span configuration for shear strength test . 18
Annex C (informative) Statistical operations . 19
Bibliography . 22

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ISO 13910:2005(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.
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 13910 was prepared by Technical Committee ISO/TC 165, Timber structures.
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ISO 13910:2005(E)
Introduction
This International Standard provides requirements for sampling, testing and assessing characteristic values of
structural properties for a specific grade and size of sawn timber for use in a timber engineering design code.
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 the derived characteristic
strength values are intended for use in structural design codes. For the characteristic strength values, the
intent is to obtain a reliable load capacity. 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.
This first edition includes clauses dealing with sampling, testing and evaluation of the characteristic values of
strength-graded timber. ISO/TC 165 plans to revise this International Standard once additional standards
(dealing with the sampling, testing, and evaluation subjects separately) have been developed.

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INTERNATIONAL STANDARD ISO 13910:2005(E)

Structural timber — Characteristic values of strength-graded
timber — Sampling, full-size testing and evaluation
1 Scope
This International Standard specifies sampling, full-size testing and evaluation procedures for the assessment
of the characteristic values of the structural properties of sawn timber for use in codes dealing with structural
engineering design. It provides methods for establishing equivalency with other standards for the testing and
evaluation of characteristic properties of structural timber.
It is applicable to sawn timber of rectangular cross-section subjected to a short-duration (approx. 1 min) load.
Its evaluation procedure is not intended to be used for quality-control purposes or for acceptance of parcels of
timber.
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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
characteristic value
percentile of a statistical distribution estimated with a specified degree of accuracy
NOTE The characteristic values used are either the mean value of the sample or an estimate of the 5-percentile
value.
3.2
grade
population of timber with defined characteristic values
3.3
p-percentile
value for which the probability of getting lower values is p percent
3.4
piece of timber
timber of rectangular cross-section and length manufactured for construction purposes
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ISO 13910:2005(E)
3.5
population of strength-graded timber
all available pieces of structural timber that are covered by a defined set of parameters such as source,
species, size and grade
3.6
reference population
population of strength-graded timber, for which the measured characteristic strength properties can be
expected to remain constant
3.7
sample size
number of pieces or specimens selected from a specified population
3.8
test specimen
length of timber, cut from a piece, for purposes of testing to evaluate a timber property
3.9
thickness
d
lesser dimension, perpendicular to the longitudinal axis of a piece of timber
3.10
width
b
greater dimension, perpendicular to the longitudinal axis of a piece of timber
4 Symbols and abbreviated terms
4.1 General notation
b width of a rectangular piece or specimen of timber, expressed in millimetres
b width of a rectangular piece or specimen of timber under compression, expressed in millimetres
c
CV coefficient of variation
d thickness of a rectangular piece or specimens 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
K grain stiffness
k importance factor

imp
k sampling factor
samp
k size factor
size
L length along a piece or specimen of timber, expressed in millimetres
L length test specimen subjected to torsion forces, expressed in millimetres
T
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ISO 13910:2005(E)
l length cut from a specimen, expressed in millimetres
h
l lever arm of applied torsion load, expressed in millimetres
t
N sample size
p percentile
e displacement of beam, expressed in millimetres
m mass of specimen, expressed in kilograms
w mass of water/mass of wood equivalent to moisture content
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% by mass moisture content
12
ρ density, expressed in kilograms per cubic metre, at time of test
test
4.2 Subscripts
0,1b value at deformation of 0,1b
0,05 5-percentile value
0 property in a direction 0° to the grain
90 property in a direction of 90° to the grain
c compression
data statistical property of the data
k characteristic value
l lower limit of a characteristic value
m bending
mean mean value
ref value for a reference size
spec value for a specific size
std standard
t tension
tail property related to the tail of a statistical distribution
u upper limit of a characteristic value
ult value at failure
v shear
y value for specific value of y on graph
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ISO 13910:2005(E)
5 Sampling
The parameters defining the reference population shall be comprehensively defined in terms of species and
other factors such as source, size, grade and method of grading.
All test specimens shall be cut from pieces that have been selected to be representative of a reference
population. Representation of the reference population may be obtained by selecting pieces at random from
the reference population. However, improved representation can be obtained if all population parameters,
such as the proportion of pieces produced by each mill, are replicated in the sample selected for testing.
A minimum sample size of 40 shall be used for each grade or size or property to be evaluated. A sample size
of greater than 40 is recommended so as to provide more reliable characteristic values for strength without
having to introduce a penalty factor as related to sample size (see 9.2.1).
6 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 8).
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 or 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.
As specified in Clause 5, a minimum sample size of 40 shall be used for each grade/size/property.
7 Test conditions
Unless otherwise specified in this International Standard, test procedures shall be in accordance with
ASTM D198. The reference moisture content at the time of testing should be consistent with conditioning at a
temperature of 20 °C and 65 % 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.
For the reference conditioning temperature and humidity, the equilibrium moisture content for solid timber
shall be approximately 12 %.
The reference temperature at the time of testing shall be 20 °C.
The rate of loading shall be one that leads to failure at about one minute.
At the time of testing, the moisture content of the timber, the temperature of the timber, and the time to failure
shall be recorded.
8 Test configurations
8.1 Density
The specimens for the measurement of density shall comprise the full cross-section of the piece of timber.
The length of the test specimen shall be not less than b. The mass, m, and moisture content, w, are measured
for each test specimen. The density at the time of test, ρ , shall be calculated from
test
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ISO 13910:2005(E)
9
m ×10
ρ = (1)
test
Ldb
The density at 12 % by mass moisture content, ρ , shall be calculated from
12
1,12

ρρ= (2)
12 test

1+ w

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 an electrical resistance
meter, provided that the meter is calibrated against moisture content measurements determined by the oven
dry method. Where such electrical moisture meter measurements are made, they should be made at two or
three locations along each specimen.
8.2 Bending strength and stiffness
The bending strength and stiffness test configuration shall be as shown in Figure 1. A beam of span 18b shall
be loaded at two points equally spaced between the end supports, with each load equal to F/2. A random
edge of the beam shall be chosen to be the tension edge. If the beam has a slenderness where there could be
a tendency to buckle during loading, then lateral restraints may be used to restrain the buckling. Such
restraints shall not provide any resistance to movement in the direction of the loading.

Key
1 rocker slider
2 bearing plate
Figure 1 — Test set-up for measuring bending strength and stiffness
Measurement of the modulus of elasticity, E, shall be undertaken by measurement of e, the centrepoint
deflection of the centreline of the beam relative to the position of the centreline at the ends of the beam, the
deflection of point B relative to points A and C as shown in Figure 1. Where this is not possible, an acceptable
conservative alternative is to measure the deflection of the centrepoint of the bottom surface of the beam
relative to the end supports of the beam.
The applied load F shall be increased until the beam fails in bending or in a mode other than bending.
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ISO 13910:2005(E)
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 and calculated from
3
23 LF ∆  1
E=× × × (3)
m
  
108be∆ d
  
The range of 10 % to 40 % of the maximum load should be used to determine ∆F/∆e.
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.
The bending strength f shall be calculated from
m
F L
ult
f = (4)
m
2
db
where
F is the value of the applied load at failure (ultimate load).
ult
8.3 Tension strength parallel to the grain
The tension strength parallel to the grain test configuration shall be as shown in Figure 2. The specimen
length between grips shall be 8b + 2 000 mm. The specimen shall be loaded to failure.
Dimensions in millimetres

Key
1 tension grip
Figure 2 — Test set-up for measuring tension strength parallel to the grain
The tension strength f shall be calculated from
t,0
F
ult
f = (5)
t,0
db
where
F is the value of the applied load at failure (ultimate load).
ult
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ISO 13910:2005(E)
8.4 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 of a total length 8b + 2 000 mm. 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 10d for buckling about the minor axis and 10b for buckling about the major axis. The lateral
restraint shall not provide any resistance in the direction of the loading.
Dimensions in millimetres

Key
1 lateral restraint
Figure 3
...