ISO/TR 12471:2004
(Main)Computational structural fire design — Review of calculation models, fire tests for determining input material data and needs for further development
Computational structural fire design — Review of calculation models, fire tests for determining input material data and needs for further development
ISO/TR 12471:2004 gives a review of the advances that have been made in measuring and understanding how structural materials respond to fire in terms of changes in their elevated temperature, and physical and mechanical characteristics, and to identify areas where further work is necessary to generate the data required. Analytical methods for heat transfer are combined with mechanical models to calculate structural behaviour from single elements up to complete frames under real fire and ISO Standard furnace heating conditions. ISO/TR 12471:2004 reviews advances in computational analysis and indicates how these can be used with probabilistic analysis to provide a risk-based approach to structural fire engineering design.
Conception de calcul des feux de structures - État des travaux des modèles de calcul et d'essais au feu pour la détermination des données de base requises et des besoins du développement ultérieur
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 12471
First edition
2004-11-15
Computational structural fire design —
Review of calculation models, fire tests
for determining input material data and
needs for further development
Conception de calcul des feux de structures — État des travaux des
modèles de calcul et d'essais au feu pour la détermination des données
de base requises et des besoins du développement ultérieur
Reference number
©
ISO 2004
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ii © ISO 2004 – All rights reserved
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Internationally applied methods for structural fire engineering design . 1
2.1 Models for thermal exposure. 2
2.2 Models for structural behaviour . 6
[56]
3 Characteristics of a reliability-based structural fire engineering design . 7
3.1 Structural fire engineering design based on FORM approximation. 7
3.2 Structural fire engineering design based on practical design format. 10
[56]
4 Predictive model capabilities: uncertainties of design components . 13
5 Main components of structural fire engineering design. 17
5.1 Design fire exposure. 17
5.2 Thermal material properties and transient temperature state. 25
5.3 Mechanical material properties and structural behaviour. 29
6 Need for further development of calculation models and related computer programs
for structural fire design: Examples . 40
6.1 Complete process of structural fire design . 40
6.2 Main components of structural fire design . 41
6.2.1 Fire exposure. 41
6.2.2 Thermal and mechanical behaviour. 41
7 Need for fire tests to determine input material data for structural fire design. 42
7.1 Properties related to fire load density and fire exposure . 42
7.2 Thermal material properties. 43
7.3 Mechanical material properties . 44
Bibliography . 46
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
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.
ISO/TR 12471 was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 2, Fire
containment.
iv © ISO 2004 – All rights reserved
Introduction
Considerable advances have been made in recent years in understanding the behaviour of fires in their
development and impact upon buildings. Coupled with developments in computational techniques, it is now
possible to predict how structures will behave at the fire limit state (i.e. under fire conditions).
As a result of the high level of international fire research in recent decades, more and more components and
systems are becoming amenable to analytical and computer modelling. Considerable progress has been
made concerning such phenomena and procedures as:
reaction of materials to fire;
fire growth in a compartment;
fully developed compartment fire;
fire spread between buildings;
fire behaviour of load-bearing and separating building structures;
smoke filling in enclosures and smoke movement in escape routes and multi-storey buildings;
interaction of sprinklers and fire, including sprinkler and fire venting interaction;
process of escape; and
systems approach to the overall fire safety of a building, in its most general form comprising fire
development models interacting with human response models.
This progress in fire research has led to consequent changes in the field of codes, specifications, and
recommendations for fire engineering. Some characteristic trends in these changes are:
a) improved connection to real fire scenarios;
b) increase in extent of design, based on functional requirements and performance criteria;
c) development of new test methods, that are, as far as possible, material-independent and related to well-
defined phenomena and properties;
d) increase in application of reliability-based analytical design;
e) extended use of integrated assessments; and
f) introduction of goal-oriented systems of analysis of total, active and passive fire protection for a building.
The most manifest verification of these developing trends probably relates to the fire engineering design of
load-bearing and separating structures. An analytical determination of the fire resistance of structural
elements is being approved by authorities in more and more countries as an alternative to the internationally
predominant design that is based on the results of the standard fire resistance test and connected
classification. The further step to permit a general practical application of an analytical design, based on a
natural compartment fire concept, was taken by Swedish authorities as early as 1967. Since then, a few other
countries have been officially open to the possibility of structural fire design.
A significant contribution was made by the Fire Commission of the Conseil International du Bâtiment, CIB
W14, in the form of a state-of-the-art report, in 1983. The report presented a conceptual approach towards a
[1]
probability-based design guide on structural fire safety , supplemented in 1986 by a model code/design
[2]
guide . These design guides are important aids in drafting corresponding national regulations and
recommendations. For European countries, the Eurocodes (see references [3] to [10] in the Bibliography)
issued as European Prestandards and supplemented with national application documents, certainly will
contribute to increased practical use of analytical structural fire design methods.
A problem arises between material-related codes and the general code. The material-related codes focus very
strongly on the fire design, based on thermal exposure according to the standard fire resistance test.
However, the general code, specifying the basis of design and mechanical and thermal actions on
fire-exposed structures, also gives some guidance, in the form of informative annexes, regarding the
alternate structural fire design, based on a parametric fire exposure determined by fire models or specified
temperature-time curves.
An analytical fire engineering design can now be performed in most cases for steel structures. Validated
material models for the mechanical behaviour of concrete under transient high-temperature
[11] to [13] [14] to [16]
conditions and thermal models for a calculation of the charring rate in wood exposed to fire ,
developed in recent decades, have significantly enlarged the area of practical application of an analytical
structural fire design. To support this application, design diagrams and tables have been computed and
published, giving directly, on the one hand, the temperature state of the fire-exposed structure, and on the
other, a further transfer to the corresponding load-bearing capacity of the structure, for instance see
references [17] to [47] in the Bibliography.
The following clauses begin with a summary of internationally applied methods for a structural fire engineering
design. With this survey as general background, the characteristics of a reliability-based approach are
described. In order to review the need for further development of calculation models and for fire tests to get
the input data required for the design, the design alternative, based on a simulated fire exposure, has been
chosen for presentation. For other design alternatives, applied in practice, the need for calculation models and
related input data is less comprehensive than for the more general approach being dealt with. The
presentation is followed by a discussion about uncertainty in the design process.
Following this background presentation of the reliability-based design process and its inherent uncertainties,
the remaining document is devoted to related deterministic models, comprising the fire exposure and the
thermal and mechanical behaviour of the structure. These models are supplemented with a survey of the
material input data required for the structural fire engineering design. Finally, conclusions are drawn regarding
the need for further development of calculation models and tests to determine the input material data required
for the structural fire design.
vi © ISO 2004 – All rights reserved
TECHNICAL REPORT ISO/TR 12471:2004(E)
Computational structural fire design — Review of calculation
models, fire tests for determining input material data and needs
for further development
1 Scope
This Technical Report gives a review of the advances that have been made in measuring and understanding
how structural materials respond to fire in terms of changes in their elevated temperature, and physical and
mechanical characteristics, and to identify areas where further work is necessary to generate the data
required. Analytical methods for heat transfer are combined with mechanical models to calculate structural
behaviour from single elements up to complete frames under real fire and ISO Standard furnace heating
conditions. This Technical Report reviews advances in computational analysis and indicates how these can be
used with probabilistic analysis to provide a risk-based approach to structural fire engineering design.
2 Internationally applied methods for structural fire engineering design
The methods available at present for a structural fire engineering design can systematically be characterized
[1] [2] [37]
with reference to the matrix according to Table 1 .
The matrix is
...
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