ISO 2394:2015

INTERNATIONAL ISO
STANDARD 2394
Fourth edition
2015-03-01
General principles on reliability for
structures
Principes généraux de la fiabilité des constructions
Reference number
ISO 2394:2015(E)
©
ISO 2015

---------------------- Page: 1 ----------------------
ISO 2394:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015
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
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
Published in Switzerland
ii © ISO 2015 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 2394:2015(E)

Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Terms and definitions . 1
2.1 General terms . 1
2.2 Terms related to design and assessment . . 5
2.3 Terms related to actions, action effects, and environmental influences . 8
2.4 Terms related to structural response, resistance, material properties, and
geometrical quantities .11
3 Symbols .12
3.1 General .12
3.2 Latin upper case letters .12
3.3 Latin lower case letters.13
3.4 Greek letters .13
3.5 Subscripts .14
4 Fundamentals .14
4.1 General .14
4.2 Aims and requirements to structures .14
4.2.1 Fundamental requirements to structures .14
4.2.2 Target performance level .15
4.3 Conceptual basis .16
4.3.1 Decisions concerning structures .16
4.3.2 Structural performance modelling .17
4.3.3 Uncertainty and treatment of knowledge .17
4.4 Approaches.18
4.4.1 General.18
4.4.2 Risk-informed and reliability-based approaches .18
4.4.3 Semi-probabilistic approaches .20
4.5 Documentation .20
5 Performance modelling .21
5.1 General .21
5.1.1 Structural performance and limit state concept.21
5.1.2 Performance and performance indicators .21
5.1.3 Basic performance requirement and design situations .21
5.1.4 Levels of verification.21
5.2 Performance model .22
5.2.1 General.22
5.2.2 Time-dependent aspects .22
5.2.3 System aspects .22
5.3 Limit states .23
5.3.1 Ultimate limit state .23
5.3.2 Serviceability limit states .23
5.3.3 Condition limit states .24
5.3.4 Limit state function.24
© ISO 2015 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 2394:2015(E)

Contents Page
6 Uncertainty representation and modelling .25
6.1 General .25
6.1.1 Types of uncertainty .25
6.1.2 Treatment of uncertainty .26
6.1.3 Interpretation of probability .26
6.1.4 Probabilistic models .26
6.1.5 Population/outcome space .26
6.1.6 Hierarchical modelling of uncertainty .27
6.2 Models for structural analysis .27
6.2.1 General.27
6.2.2 Actions and environmental influences .28
6.2.3 Geometrical properties .30
6.2.4 Material properties .30
6.2.5 Responses and resistances .31
6.3 Models for consequences .33
6.4 Model uncertainty .34
6.5 Experimental models .34
6.6 Updating of probabilistic models .35
7 Risk-informed decision making .35
7.1 General .35
7.2 System identification .35
7.3 System modelling .36
7.4 Risk quantification .36
7.5 Decision optimization and risk acceptance.36
8 Reliability-based decision making .37
8.1 General .37
8.2 Decisions based on updated probability measures .38
8.3 Systems reliability versus component reliability .38
8.4 Target failure probabilities .39
8.5 Calculation of the probability of failure .39
8.5.1 General.39
8.5.2 Time-invariant reliability problems .40
8.5.3 Transformation of time-variant into time-invariant problems .40
8.5.4 Out-crossing approach . .40
8.6 Implementation of probability-based design .41
9 Semi-probabilistic method .41
9.1 General .41
9.2 Basic principles.41
9.3 Representative and characteristic values .42
9.3.1 Actions .42
9.3.2 Resistances . . .43
9.4 Safety formats .43
9.4.1 General.43
9.4.2 Partial factor method .44
9.4.3 The design value method .46
9.5 Verification in case of cumulative damage .47
Annex A (informative) Quality management .48
Annex B (informative) Lifetime management of structural integrity .55
Annex C (informative) Design based on observations and experimental models .62
Annex D (informative) Reliability of geotechnical structures .71
Annex E (informative) Code calibration .79
iv © ISO 2015 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 2394:2015(E)

Contents Page
Annex F (informative) Structural robustness .88
Annex G (informative) Optimization and criterion on life safety .100
Bibliography .110
© ISO 2015 – All rights reserved v

---------------------- Page: 5 ----------------------
ISO 2394:2015(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 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 98, Bases for design of structures, SC 2, Reliability
of structures.
This fourth edition cancels and replaces the third edition (ISO 2394:1998), which has been technically
revised.
vi © ISO 2015 – All rights reserved

---------------------- Page: 6 ----------------------
ISO 2394:2015(E)

Introduction
The present fourth edition of this International Standard is intended to reflect advances in the common
basis for decision making related to load-bearing structures relevant to the construction industry.
Advances range from the development of systematic and rational treatment of risk to implementation of
reliability-based design through codes and standards.
Compliance with this International Standard should therefore promote harmonization of design practice
internationally and unification between the respective codes and standards such as for actions and
resistances for the respective structural materials.
The principles and appropriate instruments to ensure adequate levels of reliability provide for special classes
of structures or projects where the common experience base need to be extended in a rational manner.
In particular, a risk framework has been introduced which is scenario based, facilitates unified modelling
approaches over different applications, accounts for consequences of both a direct and indirect nature,
and has emphasis on robustness.
Whereas requirements to safety and reliability in the previous edition of this International Standard
took their basis in efficiency requirements of a heuristic character, these are now based on risk
considerations and socio-economics. This, in turn, facilitates a more relevant use of the International
Standard in the context of sustainable societal developments and adaptation for application of the
International Standard in different nation states in accordance with economic capacity and preferences.
The present International Standard, thus, enables the possibility to regulate, verify, and document the
adequate safe performance of structures and also to consider them in a broader sense as part of societal
systems. The International Standard provides for approaches at three levels, namely the following:
— risk informed;
— reliability based;
— semi-probabilistic.
[8]
The methodical basis for this edition of ISO 2394 is described in the Probabilistic Model Code and
[9]
Risk Assessment in Engineering — Principles, System Representation and Risk Criteria by the Joint
Committee on Structural Safety (JCSS), and EN 1990 (2007), where the reader will find additional
information of relevance for its use.
Informative Annexes are included to this International Standard as a support to its users in the
interpretations and use of the principles contained in its clauses.
© ISO 2015 – All rights reserved vii

---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO 2394:2015(E)
General principles on reliability for structures
1 Scope
This International Standard constitutes a risk- and reliability-informed foundation for decision making
concerning design and assessment of structures both for the purpose of code making and in the context
of specific projects.
The principles presented in this International Standard cover the majority of buildings, infrastructure,
and civil engineering works, whatever the nature of their application and use or combination of the
1)
materials used . The application of this International Standard will require specific adaptation and
2)
detailing in special cases where there are potentially extreme consequences of failure .
This International Standard is intended to serve as a basis for those committees responsible for the task
of preparing international standards, national standards, or codes of practice in accordance with given
objectives and context in a particular country.
The present International Standard describes how the principles of risk and reliability can be utilized to
support decisions related to the design and assessment of structures and systems involving structures
over their service life. Three different but related levels of approach are facilitated, namely, a risk-
informed, a reliability-based, and a semi-probabilistic approach.
The general principles are applicable to the design of complete structures (buildings, bridges, industrial
structures, etc.), the structural elements and joints making up the structures and the foundations. The
principles of this International Standard are also applicable to the successive stages in construction,
the handling of structural elements, their erection, and all work on-site, as well as the use of structures
during their design working life, including maintenance and rehabilitation, and decommissioning.
Risk and reliability are concepts accounting for and describing actions, structural response, durability,
life-cycle performance, consequences, design rules, workmanship, quality control procedures, and
national requirements, all of which are mutually dependent.
The application of this International Standard necessitates knowledge beyond what is contained in
the Clauses and the Annexes. It is the responsibility of the user to ensure that this knowledge is
available and applied.
2 Terms and definitions
2.1 General terms
2.1.1
structure
organized combination of connected parts including geotechnical structures designed to provide
resistance and rigidity against various actions
2.1.2
structural member
physically distinguishable part of a structure, e.g. column, beam, plate, foundation
1) The present International Standard is completely general from the perspective of basic principles and can be
applied for any structure below, on, and over the surface of the Earth.
2) This concerns, for example, structures of nuclear power plants and offshore oil and gas facilities in highly
sensitive environments.
© ISO 2015 – All rights reserved 1

---------------------- Page: 8 ----------------------
ISO 2394:2015(E)

2.1.3
system
bounded group of interrelated, interdependent, or interacting members forming an entity that achieves
a defined objective in its environment through interaction of its parts and interactions of its parts with
the environment
2.1.4
structural system
load-bearing members of a building or civil engineering structure and the way in which these members
function together and interact with the environment
2.1.5
requirement
demand with respect to structural aspects like safety for people and environment, functionality, usage,
and commitment of resources and cost efficiency
2.1.6
compliance
fulfilment of specified requirements
2.1.7
life cycle
life cycle incorporates initiation, project definition, design, construction, commissioning, operation,
maintenance, refurbishment, replacement, deconstruction, and ultimate disposal, recycling, or re-use
of the structure (or parts thereof), including its components, systems, and building services
2.1.8
reliability
ability of a structure or structural member to fulfil the specified requirements, during the working life,
for which it has been designed.
Note 1 to entry: Reliability is often expressed in terms of probability.
Note 2 to entry: Reliability covers safety, serviceability, and durability of a structure.
2.1.9
structural safety
ability (of a structure or structural member) to avoid exceedance of ultimate limit states, including the effects
of specified accidental phenomena, with a specified level of reliability, during a specified period of time
2.1.10
durability
capability of a structure or any structural member to satisfy with planned maintenance the design
performance requirements over a specified period of time under the influence of the environmental actions
2.1.11
exposure events
events which may cause damage or otherwise affect the performance indicators for the structure
2.1.12
assessment
total set of activities performed in order to verify the reliability of an existing structure
2.1.13
upgrading
modifications of an existing structure, construction works, and procedures to improve its structural
performance or facilitate its use for new purposes
2.1.14
repair (of a structure)
restoring the condition of a structure that has been damaged or deteriorated
2 © ISO 2015 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 2394:2015(E)

2.1.15
rehabilitation
repairing or upgrading of an existing structure
2.1.16
monitoring
frequent or continuous, normally long-term, observation or measurement of structural conditions or
actions or structural response
2.1.17
inspection
on-site examination within the scope of quality control and condition assessment aiming to assess the
present condition of a structure
2.1.18
constituent events
events associated with damage or failure of structural members or parts of these, such as individual
cross sections and joints
2.1.19
reliability-based design
design procedure that is subjected to prescribed reliability level of the structure
2.1.20
...