ISO 12122-2:2014

INTERNATIONAL ISO
STANDARD 12122-2
First edition
2014-03-01
Timber structures — Determination
of characteristic values —
Part 2:
Sawn timber
Structures en bois — Détermination des valeurs caractéristiques —
Partie 2: Bois massif
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 1
5 Reference Population . 1
6 Sampling . 2
6.1 Sampling method . 2
6.2 Sample size . 2
7 Sample conditioning . 2
8 Test data . 2
8.1 Test method . 2
8.2 Test data compatible with product description . 2
9 Evaluation of characteristic values for structural properties . 3
9.1 Structural properties . 3
9.2 Characteristic modulus of elasticity . 3
9.3 Characteristic values of strength . 3
10 Report . 3
Annex A (informative) Commentary . 4
Bibliography . 7
Foreword
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The committee responsible for this document is ISO/TC 165, Structural Timber.
ISO 12122 consists of the following parts, under the general title Timber structures — Determination of
characteristic values:
— Part 1: Basic requirements
— Part 2: Sawn timber
iv © ISO 2014 – All rights reserved

Introduction
This International Standard sets out a framework for establishing characteristic values from test results
on a sample drawn from a clearly defined reference population of sawn timber. The characteristic value
is an estimate of the property of the reference population with a consistent level of confidence prescribed
in the standard.
This part of ISO 12122 is to be used in conjunction with ISO 12122-1.
This part of ISO 12122 permits the evaluation of characteristic values on testing on commercial sized
specimens of sawn timber.
This part of ISO 12122 is applicable to structural sawn timber. In some cases, characteristic values
determined in accordance with this part of ISO 12122 can be modified to become a design value.
This part of ISO 12122 has the following annexes:
— Annex A presents a commentary on this part of ISO 12122.
INTERNATIONAL STANDARD ISO 12122-2:2014(E)
Timber structures — Determination of characteristic
values —
Part 2:
Sawn timber
1 Scope
This International Standard gives methods for the determination of characteristic values for a defined
population of sawn timber products, calculated from test values.
It presents methods for the determination of
a) characteristic value of mean-based properties, and
b) characteristic value of 5th percentile-based properties.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 12122-1, Timber structures — Determination of characteristic values — Part 1: Basic requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12122-1 apply.
4 Symbols and abbreviated terms
Symbols defined in the relevant ISO product or test standard shall be used. Other symbols are defined
in ISO 12122-1.
5 Reference Population
In addition to the requirements for definition of the reference population in ISO 12122-1, the following
attributes of sawn timber may be described:
a) climate or climate range of growing region;
b) altitude or altitude range of growing region;
c) specific silvicultural practices used in the growing region;
d) soil type or range of soil types of growing region;
e) sawing patterns (e.g. backsawn or quartersawn, core wood included or excluded);
f) seasoning method (if seasoned);
g) grading or production method.
6 Sampling
6.1 Sampling method
The sampling method shall comply with the performance objective of sampling defined in ISO 12122-1.
Representation of each of the variants in the sample shall approximate the representation of the same
variants in the reference population.
The sampling method shall be documented in the report as detailed in Clause 10 and this documentation
shall indicate a response to each of the identified attributes of the reference population listed in
compliance with Clause 5 in this part of ISO 12122 and in ISO 12122-1.
6.2 Sample size
The sample size shall comply with requirements of ISO 12122-1 and shall take into account the coefficient
of variation (V) expected for the sawn timber in the reference population.
NOTE 1 See notes under the relevant clause in ISO 12122-1.
Sawn timber properties generally have larger population coefficient of variation (V), and should
therefore have a larger sample size.
NOTE 2 ISO 12122-1 gives some guidance on selecting sample size.
7 Sample conditioning
The sample storage and testing environment shall reflect conditioning in accordance with the definition
of the reference population as indicated in ISO 12122-1.
8 Test data
8.1 Test method
The test data shall be obtained from
a) ISO 13910, or
b) a standard test method appropriate for the sawn timber reference population provided equivalency
factors with ISO 13910 can be established.
NOTE 1 See notes under the relevant clause in ISO 12122-1.
NOTE 2 Test methods involve many variables that will affect results including loading configuration and rates,
specimen positioning ,and measurement methods. The level of precision of these variables must be appropriate
to the objectives of the testing and the adjustments required in 8.2.
8.2 Test data compatible with product description
Where the characteristic value is applicable to a standard size or moisture content, adjustments to the
raw test data may be required. Any adjustment shall be in accordance with ISO 12122-1 and shall be
detailed in the report.
NOTE These adjustments include those required to pool data from different test programs as outlined in
ISO 12122-1.
2 © ISO 2014 – All rights reserved

9 Evaluation of characteristic values for structural properties
9.1 Structural properties
For sawn timber, material properties shall be evaluated. These shall include modulus of elasticity and
characteristic strengths.
NOTE These are properties which when multiplied by a geometric parameter give a component capacity or
component stiffness. Examples of these properties include characteristic modulus of elasticity and characteristic
bending strength.
Determination of the characteristic values for structural properties shall be in accordance with
ISO 12122-1.
9.2 Characteristic modulus of elasticity
Characteristic modulus of elasticity value for serviceability shall be the average of the test values
evaluated in accordance with ISO 12122-1, and in the case of its use in the ultimate limit state it shall be
either the average or the 5th percentile value.
NOTE In some cases, where a reduction of modulus of elasticity is not already factored into the behaviour
equation used for design, a 5th percentile value of modulus of elasticity can be required to design for beam or
column stability.
9.3 Characteristic values of strength
9.3.1 Characteristic bearing strength
The characteristic values for bearing strength, both parallel and perpendicular to grain, shall be the
mean property obtained from results of tests.
9.3.2 Other characteristic values for strength based on the 5th percentile test value
The 75 % lower single-sided confidence limit of the test 5th percentile value shall be evaluated. Suitable
methods for evaluating the 5th percentile value of the test data and estimating the 75 % lower single-
sided confidence limit are presented in ISO 12122-1.
10 Report
The report shall comply with the requirements of ISO 12122-1.
Annex A
(informative)
Commentary
A.1 Commentary on scope
This part of ISO 12122 presents methods for determining characteristic values for only sawn structural
timber. It is to be read in conjunction with ISO 12122-1.
This part of ISO 12122 presents a uniform methodology for the evaluation of characteristic va
...