ISO/TR 24679-4:2017

TECHNICAL ISO/TR
REPORT 24679-4
First edition
2017-08
Fire safety engineering —
Performance of structures in fire —
Part 4:
Example of a fifteen-storey steel-
framed office building
Ingénierie de la sécurité incendie — Performance des structures en
situation d'incendie —
Partie 4: Exemple d'un immeuble de bureaux en structure acier de
quinze étages
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Design strategy for fire safety of structures . 3
6 Quantification of the performance of structures in fire . 3
6.1 General . 3
6.2 Step 1: Scope of the project for fire safety of structures . 4
6.2.1 Built environment characteristics . 4
6.2.2 Fuel load . 5
6.2.3 Mechanical actions . 6
6.3 Step 2: Identify objectives, functional requirements and performance criteria for
fire safety of structures . 7
6.4 Step 3: Trial design plan for fire safety of structures . 7
6.5 Step 4: Design fire scenarios and design fires . 8
6.5.1 Design fire scenarios . 8
6.5.2 Design fires (thermal actions) . 9
6.6 Step 5: Thermal response of the structure .10
6.6.1 Steel columns and beams .10
6.6.2 Other construction elements . .12
6.7 Step 6: Mechanical response of the structure .12
6.7.1 Steel columns .12
6.7.2 Steel beams .13
6.8 Step 7: Assessment against the fire safety objectives .14
6.9 Step 8: Documentation of the design for fire safety of structures .14
6.10 Factors and influences to be considered in the quantification process .15
6.10.1 Thermal properties.15
6.10.2 Mechanical strength of steel material .15
6.10.3 Uncertainty of material properties .15
7 Guidance on use of engineering methods .15
Annex A (informative) Building and framing design .16
Annex B (informative) Fuel and structural load .26
Annex C (informative) Fire temperatures .31
Annex D (informative) Maximum temperature of insulated steel elements .36
Annex E (informative) Critical temperature of steel columns, girders and beams .42
Bibliography .49
Foreword
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This document was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 4, Fire
safety engineering.
iv © ISO 2017 – All rights reserved

Introduction
This document is an example of the application of ISO 24679-1, prepared in the format of ISO 24679-1. It
includes only those subclauses of ISO 24679-1 that describe the steps of the methodology for assessing
the performance of structures in fire. It preserves the numbering of subclauses in ISO 24679-1 and so
omits numbered subclauses for which there is no text or information relevant to this example.
This example is intended to illustrate the implementation of the steps of the fire resistance assessment,
as defined in ISO 24679-1. Only steps that are considered to be relevant to this example are well-detailed
in this document. The technical contents are based on the performance based verification methods for
fire resistance in the Building Standards Law of Japan, but were slightly modified for simplicity and
compatibility with ISO 24679-1.
TECHNICAL REPORT ISO/TR 24679-4:2017(E)
Fire safety engineering — Performance of structures in
fire —
Part 4:
Example of a fifteen-storey steel-framed office building
1 Scope
This document provides a fire engineering application relative to the fire resistance assessment of a
fifteen-storey steel framed building following the methodology given in ISO 24679-1. This document
describes the adopted process which follows the same step by step procedure as that provided in
ISO 24679-1. The annexes of this document present the detailed assessment results obtained for the
most severe fire scenarios on the basis of the outcome of this specific fire safety engineering procedure
for the building.
The fire safety engineering applied in this example to the office building with respect to its fire
resistance considers specific design fire scenarios as well as the corresponding fire development.
It takes into account fully-developed compartment fires. In realistic situations, activation of fire
suppression systems and/or intervention of fire brigade are expected, but their beneficial effects are
not taken into account. It should be noted that these severe fire scenarios have been selected for fire
resistance purposes.
Global structural behaviour is not explicitly considered, but implicitly included in the calculation
formulae. Since the building of the example is located in a seismic region, principal structural elements
are rigidly connected to each other. Load redistribution from heated elements to cold surrounding
elements exists, but it's not taken into account in the design calculations. By this approach, design is
conservative, while the process of safety checking is greatly simplified and clear. As a result, all the
calculations were carried out by explicit algebraic formulae.
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, Fire safety engineering — General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943 and ISO 23932 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
design heat release of a room
amount of heat to be released in a room including movable fire load, fixed fire load and heat transferred
from adjacent rooms
Note 1 to entry: It is expressed in MJ.
3.2
equivalent fire duration time
duration of heating by a standard fire as specified in ISO 834-1 that gives equivalent thermal effect on
structural elements with a real fire
Note 1 to entry: It is expressed in min.
3.3
fixed fuel load density
heat of combustion of materials fixed to room, such as interior finish materials, equipment and so on,
per unit floor area of fire room
Note 1 to entry: It is expressed in MJ/m .
3.4
heat penetration factor
ratio of heat penetrated from adjacent rooms to the room in consideration
Note 1 to entry: It is dimensionless.
3.5
movable fuel load density
heat of combustion of movable room contents such as furniture, commodities and so on per unit floor
area of fire room
Note 1 to entry: It is expressed in MJ/m .
3.6
total heat release of a room
amount of heat possible to be released in a room including movable and fixed fire load
Note 1 to entry: It is expressed in MJ.
4 Symbols
For
...