ISO 13824:2020
(Main)Bases for design of structures — General principles on risk assessment of systems involving structures
Bases for design of structures — General principles on risk assessment of systems involving structures
This document specifies general principles of risk assessment for systems involving structures. The focus is on strategic and operational decision-making related to design, assessment, maintenance and decommissioning of structures. This also includes formulation and calibration of related codes and standards. Systems involving structures can expose stakeholders at various levels in society to significant risks. The aim of this document is to facilitate and enhance decision-making with regard to monitoring, reducing and managing risks, and preparing for emergency in an efficient, cost-effective and transparent manner. Within the broader context of risk management, risk assessment provides decision-makers with procedures to determine whether or not, and in what manner, it is appropriate to treat risks. This document provides a general framework as well as a procedure for identifying hazards and estimating, evaluating and treating risks of structures and systems involving structures. This document also provides a basis for code writers as well as designers to set reasonable target-reliability levels, such as stated in ISO 2394, based on the result of risk considerations. For existing structures, it is intended that assessment of the risks associated with the events that were not considered in the original design or with changes in use be implemented according to the principles stated in this document. This document can also be used for risk assessment of exceptional structures upon specific adaptation and detailing, the design of which is not usually within the scope of existing codes.
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INTERNATIONAL ISO
STANDARD 13824
Second edition
2020-03
Bases for design of structures —
General principles on risk assessment
of systems involving structures
Reference number
ISO 13824:2020(E)
©
ISO 2020
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ISO 13824:2020(E)
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© ISO 2020
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ISO 13824:2020(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fundamentals of risk assessment of systems involving structures.4
5 Establishment of structural engineering context . 5
5.1 Structural engineering context . 5
5.2 Establishment of design basis . 5
5.3 Assessment of existing structures . 5
5.4 Assessment of exceptional structures or extraordinary events . 5
5.5 Providing support for decisions for other contexts . 5
6 Definition of the system . 6
6.1 General . 6
6.2 Functions of the system . 6
6.3 Identification of the subsystems . 6
7 Identification of hazards and undesirable consequences . 6
7.1 Identification of possible hazards . 6
7.2 Identification of scenarios . 6
7.3 Identification of undesirable consequences . 6
7.4 Hazard screening . 7
7.4.1 General. 7
7.4.2 Hazard screening criteria . 7
8 Risk estimation . 7
8.1 Types of risk estimation . 7
8.1.1 General. 7
8.1.2 Qualitative estimation . 7
8.1.3 Semi-quantitative estimation. 8
8.1.4 Quantitative estimation . 8
8.2 Data for risk estimation . 8
8.2.1 Data collection . 8
8.2.2 Treatment and modelling of uncertainty . 8
8.3 Risk representation . 8
8.4 Estimation of probability . 9
8.4.1 General. 9
8.4.2 Probability of occurrence of hazard . 9
8.4.3 Probability of failure of structures . 9
8.5 Estimation of undesirable consequence . 9
8.6 Sensitivity and bounding analysis . 9
9 Risk evaluation .10
9.1 Risk criteria .10
9.2 Risk acceptance .11
10 Evaluation of options for risk treatment .11
10.1 General .11
10.2 Determination of options .12
10.2.1 General.12
10.2.2 Risk avoidance .12
10.2.3 Risk reduction .12
10.2.4 Risk sharing .12
10.2.5 Risk retention .12
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ISO 13824:2020(E)
10.2.6 Emergency preparedness .12
10.3 Assessment of options for risk treatment .12
10.4 Risk treatment .13
11 Documentation .13
Annex A (informative) General framework of risk management process for systems
involving structures .14
Annex B (informative) Principles in the implementation of risk assessment .19
Annex C (informative) Examples of extraordinary events and exceptional structures for
risk assessment .26
Annex D (informative) Techniques for treatment of expert opinions .28
Annex E (informative) Examples of quantitative risk representation .31
Annex F (informative) Formulae for risk estimation .35
Annex G (informative) Procedure for the estimation of consequences .39
Annex H (informative) Examples of measures for risk treatment .41
Annex I (informative) Examples of application of risk acceptance and optimization .44
Annex J (informative) Examples of risk estimation .50
Annex K (informative) Terrorism and malevolent events .55
Bibliography .60
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ISO 13824:2020(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
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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 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 is information given for the convenience of users and does not constitute an
endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 98, Bases for design of structures,
Subcommittee SC 2, Reliability of structures.
This second edition cancels and replaces the first edition (ISO 13824:2009), which has been technically
revised. The main changes compared to the previous edition are as follows:
— risk-informed approach has been newly introduced to risk assessment in order to comply with the
latest edition of ISO 2394 (ISO 2394:2015);
— requirements for treatment of uncertainty in risk estimation have been updated by introducing
requirements related to sensitivity analysis;
— requirements for risk treatment have been updated by emphasizing the importance of optimization
of prevention and mitigation measures including emergency preparedness;
— new informative annexes on examples of risk estimation of undesirable consequences caused by
human-induced or natural events have been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 13824:2020(E)
Introduction
Systems involving structures in public and private sectors depend on civil engineering technologies
and structures. Structures support missions and business functions of whole systems.
Structures are subject to multiple natural, technological and malevolent human-induced hazards.
Hazards can have adverse impacts on performance of systems involving structures, quality of life,
stakeholders’ assets inside or near structures, operations and operability, functions and reputation,
structural safety and sustainability of environment.
Given the significance of hazards, it is imperative that all stakeholders such as owners, occupants,
designers, operators, regulators at all levels and at all phases of the lifecycle of systems involving
structures understand their responsibilities for achieving adequate structural safety, structural
functionality and managing risk.
This document provides a common basis for assessing risk relevant to planning, design, assessment,
maintenance, decommissioning and removal of structures, in accordance with ISO 31000.
In risk assessment, hazard identification and the estimation of consequence are primary procedures.
For these, it is essential to assess the risk of systems involving structures rather than just the structures,
since structural failure has significant consequences for systems, and a failure of systems such as fire
protection systems can cause serious damages. However, actions for risk treatment are taken within
the scope of structural design. Such considerations are reflected in the title of this document.
This document is intended to serve as a basis, along with other relevant standards on risk management,
for those assessing risk for systems involving structures.
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INTERNATIONAL STANDARD ISO 13824:2020(E)
Bases for design of structures — General principles on risk
assessment of systems involving structures
1 Scope
This document specifies general principles of risk assessment for systems involving structures. The
focus is on strategic and operational decision-making related to design, assessment, maintenance
and decommissioning of structures. This also includes formulation and calibration of related codes
and standards. Systems involving structures can expose stakeholders at various levels in society to
significant risks. The aim of this document is to facilitate and enhance decision-making with regard to
monitoring, reducing and managing risks, and preparing for emergency in an efficient, cost-effective
and transparent manner. Within the broader context of risk management, risk assessment provides
decision-makers with procedures to determine whether or not, and in what manner, it is appropriate to
treat risks.
This document provides a general framework as well as a procedure for identifying hazards and
estimating, evaluating and treating risks of structures and systems involving structures. This
document also provides a basis for code writers as well as designers to set reasonable target-reliability
levels, such as stated in ISO 2394, based on the result of risk considerations. For existing structures, it is
intended that assessment of the risks associated with the events that were not considered in the original
design or with changes in use be implemented according to the principles stated in this document. This
document can also be used for risk assessment of exceptional structures upon specific adaptation and
detailing, the design of which is not usually within the scope of existing codes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 2394, General principles on reliability for structures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
acceptable risk
level of risk (3.9) that an individual or society accepts or tolerates to secure certain benefits
3.2
cost/benefit analysis
analysis contributing to decision-making on whether to adopt a project or a plan by quantifying and
comparing its costs and benefits
3.3
extraordinary event
very rare event that causes very severe consequences
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ISO 13824:2020(E)
3.4
failure
state which does not meet required performance objectives due to structural damage and/or loss of
function
Note 1 to entry: Failure includes insufficient load-bearing capacity or inadequate serviceability of a structure
(3.21) or structural member, or rupture or excessive deformation of the ground, in which the strengths of soil or
rock are significant in providing resistance.
3.5
hazard
potential source of undesirable consequences (3.23)
Note 1 to entry: A hazard can be a risk (3.9) source (see ISO Guide 73). Examples of hazards include a possible
abnormal action or environmental influence, insufficient strength or stiffness, or excessive detrimental deviation
from intended dimensions (see ISO 2394).
3.5.1
hazard identification
process to find, list and characterize hazards (3.5)
3.5.2
hazard curve
exceedance probability of a specified hazard (3.5) intensity for a specified period of time
3.5.3
hazard screening
process of identifying significant hazards (3.5) for consideration during risk assessment (3.11) of systems
(3.22) involving the structures (3.21)
3.6
option
possible measure for managing risk (3.9)
Note 1 to entry: Doing nothing can be one of the feasible options.
3.7
residual risk
risk (3.9) remaining after risk treatment (3.17)
3.8
resilience
ability of a system (3.22) to reduce likelihood of failure (3.4), to absorb effects of such failure if it occurs
and to recover quickly after failure
3.9
risk
effect of uncertainty on objectives
Note 1 to entry: Risk is generally described as a combination of the probability or frequency of occurrence of an
event and the magnitude of its consequence.
Note 2 to entry: From the viewpoint of the decision theory, risk is defined as the expected value of all undesirable
consequences, i.e. the sum of all the products of the consequences of an event and their probabilities. (see
ISO 2394).
[SOURCE: ISO 2394:2015, 2.1.40, modified — Note 1 has been added.]
3.10
risk acceptance
decision to accept a risk (3.9) to secure certain benefits
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ISO 13824:2020(E)
3.11
risk assessment
overall process of establishment of structural engineering context (3.19), definition of system (3.22),
identification of hazards (3.5) and consequences, risk estimation (3.15), risk evaluation (3.16) and
evaluation of treatment options (3.6)
3.12
risk communication
exchange or sharing of information about risk (3.9) among the decision-makers and stakeholders (3.20)
Note 1 to entry: The information can relate to the existence, nature, form, probability, severity, acceptability,
treatment or other aspects of risk.
Note 2 to entry: Engineers are the main source for risk information and should encourage decision-makers and
stakeholders to communicate with each other. Some engineers are part of, or support, the decision-makers.
3.13
risk control
actions implementing risk-management decisions
Note 1 to entry: Risk control can involve monitoring, re-evaluation and compliance with decisions.
3.14
risk criteria
criteria against which the significance of the results of the risk (3.9)analysis is evaluated
Note 1 to entry: The criteria are generally based on regulations, standards, experience, and/or theoretical
knowledge used as a basis for risk acceptance.
Note 2 to entry: Risk criteria can depend on associated costs and benefits, legal and statutory requirements,
socio-economic and environmental aspects, the concerns of stakeholders, priorities and other inputs to the
assessment.
3.15
risk estimation
process of assigning values to the probability of occurrence of events and their consequences
3.16
risk evaluation
process of comparing the estimated risk (3.9) with given risk criteria (3.14) to determine the significance
of the risk
Note 1 to entry: Risk evaluation is the process for assisting in the decision to accept or to treat a risk.
3.17
risk treatment
process of selection and implementation of measures to mitigate risk (3.9)
3.18
scenario
description of sequences or combinations of events in time and space and their inter-relationship given
the occurrence of a hazard (3.5)
3.19
structural engineering context
background or reasons why the risk assessment (3.11) is implemented from structural perspectives
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ISO 13824:2020(E)
3.20
stakeholder
any individual, group, organization or authority that can affect, be affected by, or perceive itself to be
affected by, a risk (3.9)
Note 1 to entry: The decision-maker is sometimes categorized as one of the stakeholders.
3.21
structure
arrangement of materials that is expected to withstand certain actions and to perform some intended
function
3.22
system
delimited group of interrelated, interdependent or interacting objects that is assessed for a risk (3.9)
Note 1 to entry: This definition implies that the system is identifiable and is made up of interacting elements or
subsystems, that all elements are identifiable, and that the boundary of the system can be identified.
Note 2 to entry: A system involving structures includes the structural system defined in ISO 2394 as a subsystem.
3.23
undesirable consequence
direct and indirect harm due to structural damage, functionality loss, etc., stated in terms of personal
injury, death, environmental damage, societal harm and/or monetary loss
Note 1 to entry: There can be more than one undesirable consequence from an event.
Note 2 to entry: Consequences can be expressed qualitatively or quantitatively.
Note 3 to entry: Both immediate and long-term consequences are included.
3.24
undesirable event
event that can have undesirable consequences (3.23)
Note 1 to entry: Undesirable events are sometimes caused by natural, technological and human-induced hazards.
4 Fundamentals of risk assessment of systems involving structures
Risk assessment of system involving structures shall be done within the scope of the prescribed
risk management; see Annexes A and B. Risk assessment shall consist of the following elements: the
establishment of the structural engineering context, the definition of system, the identification of
hazards and consequences, the risk estimation, the risk evaluation and the evaluation of options for
risk treatment.
NOTE 1 A risk management process typically consists of the establishment of risk-management goals, a risk
assessment, a risk treatment, communication and consultation, and a monitoring and review; see Annex A. The
establishment of risk-management goals includes the development of risk criteria; see 9.1.
NOTE 2 A risk management process is not a one-way process but an iterative process; see Annexes A and B.
There shall be thorough communication and appropriate consultation with the stakeholders for each
element of the risk assessment. After the risk assessment is complete, its results shall be conveyed in a
suitable manner so that appropriate decisions can be made and the stakeholders can understand them.
The decision concerning structures shall conform to requirements specified in ISO 2394.
The appropriateness of all elements of the risk assessment shall be reviewed in order to ensure continuous
improvement of the risk management process, including risk assessment; see Annexes A and B.
The results of risk assessment shall be documented for future reference to guarantee that decisions are
understood and to assist in the continuous improvement of the process; see Clause 11.
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ISO 13824:2020(E)
5 Establishment of structural engineering context
5.1 Structural engineering context
Structural engineering context shall be established as the first step of risk assessment. Typical
structural engineering contexts or typical applications of risk assessment of systems, including
structures, are the following:
a) establishment of design basis;
b) assessment of existing structures;
c) assessment of exceptional structures and/or extraordinary events; see Annexes C and K;
d) providing support for decisions in other contexts.
Stakeholders shall be identified based on the established structural-engineering context.
NOTE 1 Examples of decisions in other contexts include situations related to operation such as inspection and
maintenance planning as well as performance and functional level
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