ISO/TR 24679-5:2023

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
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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
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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 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).
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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
...