ISO 12122-1:2014

INTERNATIONAL ISO
STANDARD 12122-1
First edition
2014-03-01
Timber structures — Determination
of characteristic values —
Part 1:
Basic requirements
Structures en bois — Détermination des valeurs caractéristiques —
Partie 1: Exigences de base
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 . 2
5 Reference population . 2
6 Sampling . 3
6.1 Sampling method . 3
6.2 Sample size . 3
7 Sample conditioning . 3
7.1 Sample moisture content . 4
7.2 Sample temperature . 4
8 Test data . 4
8.1 Test method . 4
8.2 Test data compatible with product description . 4
9 Evaluation of characteristic values for structural properties . 4
9.1 Structural properties . 4
9.2 Characteristic value based on the mean . 5
9.3 Characteristic value based on the 5th percentile test value . 5
10 Report . 5
10.1 General . 5
10.2 Reference population . 5
10.3 Sampling . 6
10.4 Test methods . 6
10.5 Analysis methods . 6
10.6 Characteristic values . 6
Annex A (normative) Analysis of data for characteristic values . 7
Annex B (informative) Commentary .12
Annex C (informative) Examples .22
Bibliography .27
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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electrotechnical standardization.
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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
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to Trade (TBT) see the following URL: Foreword - Supplementary information
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 to establish characteristic values from test results on
a sample drawn from a clearly defined reference population. The characteristic value is an estimate of
the property of the reference population with a consistent level of confidence prescribed in this part of
ISO 12122.
It is the intention that this part of ISO 12122 can be used on any structural product including but not
limited to: sawn timber, glulam, structural composite lumber, I-beams, wood-based panels, poles, and
round timber. Whenever it is used, this part of ISO 12122 alerts the user to the basic requirements
for the determination of consistent characteristic values, but for some classes of products, additional
requirements set out in other parts or Annexes to this part give further mandatory detail and explanation.
It permits the evaluation of characteristic values on testing of commercial sized specimens.
In some cases, characteristic values determined in accordance with this part of ISO 12122 may be
modified to become a design value.
This part of ISO 12122 has the following Annexes:
Annex A presents detail on a number of statistical methods that may be used in the evaluation of
characteristic values.
Annex B presents a commentary on the provisions in this part of ISO 12122.
Annex C presents examples of the use of the statistical methods.
INTERNATIONAL STANDARD ISO 12122-1:2014(E)
Timber structures — Determination of characteristic
values —
Part 1:
Basic requirements
1 Scope
This International Standard gives methods for the determination of characteristic values for a defined
population of 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.
AS/NZS 4063.2, Characterisation of structural timber — Part 2: Determination of characteristic values
ASTM D2915, Sampling and data-analysis for structural wood and wood-based products
EN 14358, Timber structures — Calculation of characteristic 5th percentile values and acceptance criteria
for a sample
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
characteristic value
value of a property taken to represent the property of a designated population using a process of
sampling, testing of specimens, and analysis
3.2
characteristic value of mean-based property
two alternative presentations of characteristic value for mean-based properties are possible:
a) the mean property obtained from results of tests on the defined product;
b) the mean property with 75 % confidence obtained from results of tests on the defined product
3.3
characteristic value of 5th percentile-based strength property
5th percentile value with 75 % confidence strength property obtained from results of tests on the
defined product
3.4
population
all of the structural timber product that meets the description of the population
Note 1 to entry: See Annex B for some examples of the use of the term population.
3.5
sample
number of single members of the population, selected to represent the population
Note 1 to entry: See Annex B for some examples of the use of the term sample.
3.6
specimen
single element used in a test; the element may be a complete member, a member that has been trimmed
to length, or a part of a member fabricated for a specific test
Note 1 to entry: See Annex B for some examples of the use of the term specimen.
4 Symbols and abbreviated terms
Symbols defined in the relevant ISO product or test standard shall be used.
In addition, the following apply:
f is the characteristic bending strength
m
k is a multiplier to give the mean property with 75 % confidence and is given in Table A1
mean, 0,75
k is a multiplier to give the 5th percentile value with 75 % confidence for a 5th percen-
0,05, 0,75
tile-based property and is given in Table A2
M is the moment capacity
n is the number of specimens in the test data
V is the coefficient of variation of the test data
X is the target difference between the reported characteristic value and the test result
Δ
5th percentile
X is a generalized test value
i
X is the average of the individual test values (X )
mean i
X is the mean property with 75 % confidence
mean, 0,75
X is the 5th percentile value from the test data
0,05
X is the 5th percentile value with 75 % confidence
0,05, 0,75
Z is the section modulus
5 Reference population
The population to which the characteristic value applies shall be fully described. The description shall
reference all of the attributes that may affect either the strength or stiffness and restrict the pieces to
the
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