ISO/TR 24679-5:2023
(Main)Fire safety engineering — Performance of structures in fire — Part 5: Example of a timber building in Canada
Fire safety engineering — Performance of structures in fire — Part 5: Example of a timber building in Canada
This document provides a fire engineering application relative to the fire resistance assessment of a multi-storey timber building according to the methodology given in ISO 24679-1. In an attempt to facilitate the understanding of the design process presented herein, this document follows the same step-by-step procedure as that given in ISO 24679-1. The fire safety engineering approach is applied to a multi-storey timber building with respect to fire resistance and considers specific design fire scenarios, which impact the fire resistance of structural members. A component-level (member analysis) approach to fire performance analysis is adopted in this worked example. Such an approach generally provides a more conservative design than a system-level (global structural) analysis or an analysis of parts of the structure where interaction between components can be assessed. An advantage of the component-level approach is that calculations can be done with the use of simple analytical models or spreadsheets. Advanced modelling using computational fluid dynamics is presented to replicate an actual office cubicle fire scenario and for assessing timber contribution to fire growth, intensity and duration, if any. The thermo-structural behaviour of the timber elements is assessed through advanced modelling using the finite element method. The fire design scenarios chosen in this document are only used for the evaluation of the structural fire resistance. They are not applicable for assessing, for example, smoke production, tenability conditions or other life safety conditions.
Ingénierie de la sécurité incendie — Performances des structures en situation d’incendie — Partie 5: Exemple d’un immeuble en bois au Canada
Le présent document développe une application de l’ingénierie de la sécurité incendie relative à l’évaluation de la résistance au feu d’un immeuble en bois de plusieurs étages conformément à la méthodologie donnée dans l’ISO 24679-1. Dans la volonté de faciliter la compréhension du processus de dimensionnement présenté ci-après, le présent document suit la même procédure par étapes que celle donnée dans l’ISO 24679-1. L’approche d’ingénierie de la sécurité incendie repose sur la résistance au feu d’un immeuble en bois de plusieurs étages et considère des scénarios d’incendie de dimensionnement spécifiques, lesquels impactent la résistance au feu des éléments structuraux. Dans l’exemple développé ci-après, il a été adopté, pour l’analyse de la tenue au feu, une approche au niveau du composant (analyse de l’élément). Une telle approche fournit généralement une conception plus prudente qu’une analyse (structurale globale) au niveau du système ou qu’une analyse des parties de la structure notamment lorsqu’une interaction entre les éléments peut être évaluée. L’approche au niveau du composant présente un avantage qui est que les calculs peuvent être effectués avec l’utilisation de modèles analytiques simples ou de tableurs. Une modélisation avancée utilisant la dynamique des fluides à l’aide d’un modèle de champs est présentée pour reproduire un scénario d’incendie réel d’une cabine de bureau et pour évaluer la contribution du bois dans la croissance, l’intensité et la durée du feu, le cas échéant. Le comportement thermo-structural des éléments en bois est évalué au moyen d’une modélisation avancée utilisant la méthode des éléments finis. Les scénarios d’incendie de dimensionnement choisis dans le présent document sont uniquement utilisés pour l’évaluation de la résistance au feu des éléments de la structure de l’immeuble. Ils ne s’appliquent pas à l’évaluation, par exemple, de la production de fumée, des conditions de tenabilité ou d’autres conditions relatives à la sécurité des personnes.
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 24679-5
First edition
2023-07
Fire safety engineering —
Performance of structures in fire —
Part 5:
Example of a timber building in
Canada
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Design strategy for fire safety of structures . 2
4.1 General design process for fire safety of structures . 2
4.2 Practical design process for fire safety of structures . 2
5 Quantification of the performance of structures in fire . 2
5.1 Step 1: Scope of the project for fire safety of structures. 2
5.1.1 Built-environment characteristics . 2
5.1.2 Fuel loads . 6
5.1.3 Mechanical actions . 8
5.2 Step 2: Identifying objectives, functional requirements and performance criteria
for fire safety of structures . 8
5.2.1 Objectives and functional requirements for fire safety of structures . 8
5.2.2 Performance criteria for fire safety of structures . 9
5.3 Step 3: Trial design plan for fire safety of structures . 10
5.4 Step 4: Design fire scenarios and design fires (thermal actions) . 10
5.4.1 General . 10
5.4.2 Design fire scenarios . 11
5.4.3 Design fires (thermal actions) .12
5.5 Step 5: Thermal response of the structure .34
5.5.1 Charring of timber .34
5.5.2 Description of the thermal properties . 37
5.5.3 Scenario 3 .38
5.5.4 Temperature beyond the char layer .50
5.6 Step 6: Mechanical response of the structure . 51
5.6.1 Description of the mechanical properties . 52
5.6.2 Scenario 3 – Beam B1 . 52
5.6.3 Scenario 3 – Column C2 .56
5.7 Step 7: Assessment against the fire safety objectives .60
5.7.1 Beam B1 .60
5.7.2 Column C2 .60
5.8 Documentation of the design for fire safety of structures . 61
5.9 Factors and influences to be considered in the quantification process . 61
5.9.1 Material properties . 61
5.9.2 Effect of continuity and restraint (interaction between elements and
materials) . 62
5.9.3 Use of test results . 62
5.9.4 Fire spread routes . 62
6 Guidance on use of engineering methods .62
6.1 Using calculation methods . 62
6.2 Using experimental methods . 62
6.3 Using engineering judgment . 62
Bibliography .64
iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document 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 92, Fire safety, Subcommittee SC 4, Fire
safety engineering.
A list of all parts in the ISO 24679 series can be found on the ISO website.
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.
iv
Introduction
This document provides an example of the application of ISO 24679-1. The procedure described in
this document is intended to follow the principles outlined in ISO 24679-1. It therefore preserves the
numbering of subclauses in ISO 24679-1, omitting numbered subclauses for which there is no text or
information relevant to this example.
The example provided in this document is intended to illustrate the implementation of the steps of
fire resistance assessment, as defined in ISO 24679-1, and to demonstrate how ISO 24679-1 can be
applied to different building regulatory systems. It is not intended to demonstrate full conformance of
a performance-based fire engineering design seeking approval. Therefore, only a limited number of fire
design scenarios and structural assessments are presented.
v
TECHNICAL REPORT ISO/TR 24679-5:2023(E)
Fire safety engineering — Performance of structures in
fire —
Part 5:
Example of a timber building in Canada
1 Scope
This document provides a fire engineering application relative to the fire resistance assessment of
a multi-storey timber building according to the methodology given in ISO 24679-1. In an attempt to
facilitate the understanding of the design process presented herein, this document follows the same
step-by-step procedure as that given in ISO 24679-1.
The fire safety engineering approach is applied to a multi-storey timber building with respect to fire
resistance and considers specific design fire scenarios, which impact the fire resistance of structural
members.
A component-level (member analysis) approach to fire performance analysis is adopted in this worked
example. Such an approach generally provides a more conservative design than a system-level (global
structural) analysis or an analysis of parts of the structure where interaction between components can
be assessed. An advantage of the component-level approach is that calculations can be done with the use
of simple analytical models or spreadsheets. Advanced modelling using computational fluid dynamics
is presented to replicate an actual office cubicle fire scenario and for assessing timber contribution to
fire growth, intensity and duration, if any. The thermo-structural behaviour of the timber elements is
assessed through advanced modelling using the finite element method.
The fire design scenarios chosen in this document are only used for the evaluation of the structural fire
resistance. They are not applicable for assessing, for example, smoke production, tenability conditions
or other life safety conditions.
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 13943, Fire safety — Vocabulary
ISO 23932-1, Fire safety engineering — General principles — Part 1: General
ISO 24679-1, Fire safety engineering — Performance of structures in fire — Part 1: General
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943, ISO 239
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.