Eurocode 3: Design of steel structures - Part 1-2: General rules - Structural fire design

1.1   Scope of prEN 1993-1-2
(1) This document provides rules for the design of steel structures for the accidental situation of fire exposure. This Part of EN 1993 only identifies differences from, or supplements to, normal temperature design.
(2) This document applies to steel structures required to fulfil a loadbearing function.
(3) This document does not include rules for separating function.
(4) This document gives principles and application rules for the design of structures for specified requirements in respect of the aforementioned function and the levels of performance.
(5) This document applies to structures, or parts of structures, that are within the scope of EN 1993 1 1 and are designed accordingly.
(6) This document is intended to be used in conjunction with EN 1991-1-2, EN 1993-1-1, EN 1993 1-3, EN 1993-1-4, EN 1993-1-5, EN 1993-1-6, EN 1993-1-7, EN 1993-1-8, EN 1993-1-11, EN 1993-1-13 or EN 1993-1-14.
1.2   Assumptions
(1) Unless specifically stated, EN 1990, EN 1991(all parts) and EN 1993-1-1 apply.
(2) The design methods given in prEN 1993-1-2 are applicable if
-   the execution quality is as specified in EN 1090-2 and/or EN 1090-4, and
-   the construction materials and products used are as specified in prEN 1993-1-1:2020, Table 5.1 and Table 5.2 and in prEN 1993-1-3:2022, Table 5.1 and Table 5.2, or in the relevant material and product specifications.
(3) In addition to the general assumptions of EN 1990 the following assumptions apply:
-   the choice of the relevant design fire scenario is made by appropriate qualified and experienced personnel, or is given by the relevant national regulation;
-   any fire protection measure taken into account in the design will be adequately maintained.

Eurocode 3: Bemessung und Konstruktion von Stahlbauten - Teil 1-2: Allgemeine Regeln - Tragwerksbemessung für den Brandfall

1.1   Anwendungsbereich von prEN 1993 1 2
(1) Dieses Dokument enthält Regeln für die Bemessung von Stahltragwerken für die außergewöhnliche Situation der Brandbeanspruchung. Dieser Teil von EN 1993 beschränkt sich auf Unterschiede oder Ergänzungen zur Bemessung für Normaltemperatur.
(2) Dieses Dokument gilt für Stahltragwerke, die Funktionen der Tragfähigkeit und/oder des Raumabschlusses erfüllen müssen.
(3) Dieses Dokument enthält keine Regeln für raumabschließende Funktionen.
(4) Dieses Dokument enthält Grundsätze und Anwendungsregeln für die Bemessung von Tragwerken für festgelegte Anforderungen im Hinblick auf die vorstehend erwähnte Funktion und die Leistungsklassen.
(5) Dieses Dokument gilt für Tragwerke oder Teiltragwerke, die in den Anwendungsbereich von EN 1993 1 1 fallen und danach bemessen werden.
(6) Dieses Dokument ist für die Anwendung in Zusammenhang mit EN 1991 1 2, EN 1993 1 1, EN 1993 1 3, EN 1993 1 4, EN 1993 1 5, EN 1993 1 6, EN 1993 1 7, EN 1993 1 8, EN 1993 1 11, EN 1993 1 13 oder EN 1993 1 14 vorgesehen.
1.2   Annahmen
(1) Sofern nicht spezifisch angegeben, gelten EN 1990, EN 1991 (alle Teile) und EN 1993 1 1.
(2) Die in prEN 1993 1 2 angegebenen Bemessungsverfahren sind anwendbar, wenn
-   die Qualität der Ausführung den Festlegungen nach EN 1090 2 und/oder EN 1090 4 entspricht; und
-   die verwendeten Baustoffe und Bauprodukte den Festlegungen nach prEN 1993 1 1:2020, Tabelle 5.1 und Tabelle 5.2, sowie prEN 1993 1 3:2022, Tabelle 5.1 und Tabelle 5.2, oder nach den maßgebenden Baustoff- und Produktspezifikationen entsprechen.
(3) Zusätzlich zu den allgemeinen Annahmen nach EN 1990 gelten die folgenden Annahmen:
-   die Wahl des maßgebenden Bemessungsbrandszenarios erfolgt durch angemessen qualifiziertes und erfahrenes Personal oder ist in der maßgebenden nationalen Regelung angegeben;
-   jede bei der Bemessung berücksichtigte Brandschutzmaßnahme wird ausreichend gewartet.

Eurocode 3 - Calcul des structures en acier - Partie 1-2 : Règles générales - Calcul du comportement au feu

1.1   Domaine d'application du prEN 1993-1-2
(1) Le présent document établit des règles de calcul des structures en acier pour la situation accidentelle d'exposition au feu. La présente partie de l'EN 1993 identifie uniquement les différences avec le calcul à température normale, ou lui apporte des compléments.
(2) Le présent document s'applique aux structures en acier devant remplir une fonction porteuse.
(3) Le présent document ne comprend pas de règles pour la fonction de compartimentage.
(4) Le présent document donne les principes et les règles d'application relatifs au calcul des structures par rapport aux exigences spécifiées eu égard à la fonction mentionnée ci-dessus et aux niveaux de performances.
(5) Le présent document s'applique aux structures, ou aux parties de structures, relevant du domaine d'application de l'EN 1993 1 1 et conçues en conséquence.
(6) Le présent document est destiné à être utilisé conjointement avec l'EN 1991-1-2, l'EN 1993-1-1, l'EN 1993 1-3, l'EN 1993-1-4, l'EN 1993-1-5, l'EN 1993-1-6, l'EN 1993-1-7, l'EN 1993-1-8, l'EN 1993 1 11, l'EN 1993-1-13 ou l'EN 1993-1-14.
1.2   Hypothèses
(1) Sauf indication contraire, l'EN 1990, l'EN 1991(toutes les parties) et l'EN 1993-1-1 s'appliquent.
(2) Les méthodes de calcul données dans le prEN 1993-1-2 sont applicables si :
-   la qualité de l'exécution est telle que spécifiée dans l'EN 1090-2 et/ou l'EN 1090-4 ; et
-   les matériaux de construction et les produits utilisés sont tels que spécifiés dans le prEN 1993 1 1:2020, Tableau 5.1 et Tableau 5.2, et dans le prEN 1993-1-3:2022, Tableau 5.1 et Tableau 5.2, ou dans les spécifications de matériaux et de produits appropriées.
(3) Outre les hypothèses générales de l'EN 1990, les hypothèses suivantes s'appliquent :
-   le choix du scénario d'incendie de calcul pertinent est fait par un personnel qualifié et expérimenté approprié, ou est indiqué par la réglementation nationale pertinente ;
-   les mesures de protection contre l'incendie prises en compte dans le dimensionnement font l'objet d'une maintenance appropriée.

Evrokod 3: Projektiranje jeklenih konstrukcij - 1-2. del: Splošna pravila - Požarnoodporno projektiranje

General Information

Status
Not Published
Public Enquiry End Date
30-May-2022
Technical Committee
Current Stage
4020 - Public enquire (PE) (Adopted Project)
Start Date
15-Mar-2022
Due Date
02-Aug-2022
Completion Date
02-Jun-2022

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SLOVENSKI STANDARD
oSIST prEN 1993-1-2:2022
01-maj-2022
Evrokod 3: Projektiranje jeklenih konstrukcij - 1-2. del: Splošna pravila -
Požarnoodporno projektiranje
Eurocode 3: Design of steel structures - Part 1-2: General rules - Structural fire design
Eurocode 3: Bemessung und Konstruktion von Stahlbauten - Teil 1-2: Allgemeine
Regeln - Tragwerksbemessung für den Brandfall
Eurocode 3 - Calcul des structures en acier - Partie 1-2 : Règles générales - Calcul du
comportement au feu
Ta slovenski standard je istoveten z: prEN 1993-1-2
ICS:
13.220.50 Požarna odpornost Fire-resistance of building
gradbenih materialov in materials and elements
elementov
91.010.30 Tehnični vidiki Technical aspects
91.080.13 Jeklene konstrukcije Steel structures
oSIST prEN 1993-1-2:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 1993-1-2:2022


DRAFT
EUROPEAN STANDARD
prEN 1993-1-2
NORME EUROPÉENNE

EUROPÄISCHE NORM

March 2022
ICS 13.220.50; 91.010.30; 91.080.13 Will supersede EN 1993-1-2:2005
English Version

Eurocode 3: Design of steel structures - Part 1-2: General
rules - Structural fire design
Eurocode 3 - Calcul des structures en acier - Partie 1-2 : Eurocode 3: Bemessung und Konstruktion von
Règles générales - Calcul du comportement au feu Stahlbauten - Teil 1-2: Allgemeine Regeln -
Tragwerksbemessung für den Brandfall
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 250.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1993-1-2:2022 E
worldwide for CEN national Members.

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prEN 1993-1-2:2022 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and symbols . 8
Terms and definitions . 8
Symbols . 9
4 Basis of design .14
General .14
Nominal fire exposure .15
Physically based fire exposure .15
Actions.16
Design values of material properties .16
Verification methods .16
Member analysis .17
Analysis of parts of the structure .17
Global structural analysis .17
5 Material properties .17
General .17
Thermal properties .18
Mechanical properties .20
6 Tabulated design data .25
7 Simplified design methods .26
General .26
Classification of cross-sections .26
Effective width for Class 4 cross-sections.27
Resistance .27
Critical temperature .39
Steel temperature development .39
8 Advanced design methods .46
General .46
Thermal analysis .46
Mechanical analysis .46
Validation of advanced design methods .47
Annex A (normative) Strain-hardening of carbon steel at elevated temperatures .48
Annex B (normative) Heat transfer to external steelwork .50
Annex C (normative) Stainless steels .68
Annex D (normative) Joints .82
Annex E (normative) Beams with large web openings .86
Bibliography .91

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European foreword
This document (prEN 1993-1-2:2022) has been prepared by Technical Committee CEN/TC 250
“Structural Eurocodes”, the secretariat of which is held by BSI. CEN/TC 250 is responsible for all
Structural Eurocodes and has been assigned responsibility for structural and geotechnical design
matters by CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1993-1-2:2005 and its corrigenda.
The first generation of EN Eurocodes was published between 2002 and 2007. This document forms
part of the second generation of the Eurocodes, which have been prepared under Mandate M/515
issued to CEN by the European Commission and the European Free Trade Association.
The Eurocodes have been drafted to be used in conjunction with relevant execution, material,
product and test standards, and to identify requirements for execution, materials, products and
testing that are relied upon by the Eurocodes.
The Eurocodes recognize the responsibility of each Member State and have safeguarded their right
to determine values related to regulatory safety matters at national level through the use of National
Annexes.
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Introduction
0.1 Introduction to the Eurocodes
The Structural Eurocodes comprise the following standards generally consisting of a number of Parts:
— EN 1990 Eurocode: Basis of structural and geotechnical design
— EN 1991 Eurocode 1: Actions on structures
— EN 1992 Eurocode 2: Design of concrete structures
— EN 1993 Eurocode 3: Design of steel structures
— EN 1994 Eurocode 4: Design of composite steel and concrete structures
— EN 1995 Eurocode 5: Design of timber structures
— EN 1996 Eurocode 6: Design of masonry structures
— EN 1997 Eurocode 7: Geotechnical design
— EN 1998 Eurocode 8: Design of structures for earthquake resistance
— EN 1999 Eurocode 9: Design of aluminium structures
— New parts are under development, e.g. Eurocode for design of structural glass
0.2 Introduction to EN 1993 (all parts)
EN 1993 (all parts) applies to the design of buildings and civil engineering works in steel. It complies
with the principles and requirements for the safety and serviceability of structures, the basis of their
design and verification that are given in EN 1990 – Basis of structural design.
EN 1993 (all parts) is concerned only with requirements for resistance, serviceability, durability and fire
resistance of steel structures. Other requirements, e.g. concerning thermal or sound insulation, are not
covered.
EN 1993 is subdivided in various parts:
EN 1993-1, Design of Steel Structures — Part 1: General rules and rules for buildings;
EN 1993-2, Design of Steel Structures — Part 2: Steel bridges;
EN 1993-3, Design of Steel Structures — Part 3: Towers, masts and chimneys;
EN 1993-4, Design of Steel Structures — Part 4: Silos and tanks;
EN 1993-5, Design of Steel Structures — Part 5: Piling;
EN 1993-6, Design of Steel Structures — Part 6: Crane supporting structures;
EN 1993-7, Design of steel structures — Part 7: Design of sandwich panels.
EN 1993-1 in itself does not exist as a physical document, but comprises the following 14 separate parts,
the basic part being EN 1993-1-1:
EN 1993-1-1, Design of Steel Structures — Part 1-1: General rules and rules for buildings;
EN 1993-1-2, Design of Steel Structures — Part 1-2: Structural fire design;
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prEN 1993-1-2:2022 (E)
EN 1993-1-3, Design of Steel Structures — Part 1-3: Cold-formed members and sheeting;
NOTE Cold formed hollow sections supplied according to EN 10219 are covered in EN 1993-1-1.
EN 1993-1-4, Design of Steel Structures — Part 1-4: Stainless steels;
EN 1993-1-5, Design of Steel Structures — Part 1-5: Plated structural elements;
EN 1993-1-6, Design of Steel Structures — Part 1-6: Strength and stability of shell structures;
EN 1993-1-7, Design of Steel Structures — Part 1-7: Strength and stability of planar plated structures
transversely loaded;
EN 1993-1-8, Design of Steel Structures — Part 1-8: Design of joints;
EN 1993-1-9, Design of Steel Structures — Part 1-9: Fatigue strength of steel structures;
EN 1993-1-10, Design of Steel Structures — Part 1-10: Selection of steel for fracture toughness and through-
thickness properties;
EN 1993-1-11, Design of Steel Structures — Part 1-11: Design of structures with tension components made
of steel;
EN 1993-1-12, Design of Steel Structures — Part 1-12: Additional rules for steel grades up to S960;
EN 1993-1-13, Design of Steel Structures — Part 1-13: Beams with large web openings;
EN 1993-1-14, Design of Steel Structures — Part 1-14: Design assisted by finite element analysis.
All subsequent parts EN 1993-1-2 to EN 1993-1-14 treat general topics that are independent from the
structural type like structural fire design, cold-formed members and sheeting, stainless steels, plated
structural elements, etc.
All subsequent parts numbered EN 1993-2 to EN 1993-7 treat topics relevant for a specific structural
type like steel bridges, towers, masts and chimneys, silos and tanks, piling, crane supporting structures,
etc. EN 1993-2 to EN 1993-7 refer to the generic rules in EN 1993-1 and supplement, modify or supersede
them, where relevant.
0.3 Introduction to prEN 1993-1-2
prEN 1993-1-2 describes the principles, requirements and rules for the structural design of steel
buildings exposed to fire. The focus in prEN 1993-1-2 is on design methods and design rules for individual
members (beams, columns, beam-columns), joints and skeletal structures (frames) regarding resistance
and stability under fire conditions.
0.4 Verbal forms used in the Eurocodes
The verb “shall" expresses a requirement strictly to be followed and from which no deviation is permitted
in order to comply with the Eurocodes.
The verb “should” expresses a highly recommended choice or course of action. Subject to national
regulation and/or any relevant contractual provisions, alternative approaches could be used/adopted
where technically justified.
The verb “may" expresses a course of action permissible within the limits of the Eurocodes.
The verb “can" expresses possibility and capability; it is used for statements of fact and clarification of
concepts.
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0.5 National Annex for prEN 1993-1-2
National choice is allowed in this standard where explicitly stated within notes. National choice includes
the selection of values for Nationally Determined Parameters (NDPs).
The national standard implementing prEN 1993-1-2 can have a National Annex containing all national
choices to be used for the design of buildings and civil engineering works to be constructed in the relevant
country.
When no national choice is given, the default choice given in this standard is to be used.
When no national choice is made and no default is given in this standard, the choice can be specified by a
relevant authority or, where not specified, agreed for a specific project by appropriate parties.
National choice is allowed in EN 1993-1-2 through notes to the following clauses:
4.5 (1) 7.5 (2) – 2 choices
The National Annex can contain, directly or by reference, non-contradictory complementary information
for ease of implementation, provided it does not alter any provisions of the Eurocodes.


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1 Scope
1.1 Scope of prEN 1993-1-2
(1) This document provides rules for the design of steel structures for the accidental situation of fire
exposure. This Part of EN 1993 only identifies differences from, or supplements to, normal temperature
design.
(2) This document applies to steel structures required to fulfil a loadbearing function.
(3) This document does not include rules for separating function.
(4) This document gives principles and application rules for the design of structures for specified
requirements in respect of the aforementioned function and the levels of performance.
(5) This document applies to structures, or parts of structures, that are within the scope of EN 1993-1-1
and are designed accordingly.
(6) This document is intended to be used in conjunction with EN 1991-1-2, EN 1993-1-1, EN 1993-1-3,
EN 1993-1-4, EN 1993-1-5, EN 1993-1-6, EN 1993-1-7, EN 1993-1-8, EN 1993-1-11, EN 1993-1-13 or
EN 1993-1-14.
1.2 Assumptions
(1) Unless specifically stated, EN 1990, EN 1991(all parts) and EN 1993-1-1 apply.
(2) The design methods given in prEN 1993-1-2 are applicable if
— the execution quality is as specified in EN 1090-2 and/or EN 1090-4, and
— the construction materials and products used are as specified in prEN 1993-1-1:2020, Table 5.1 and
Table 5.2 and in prEN 1993-1-3:2022, Table 5.1 and Table 5.2, or in the relevant material and product
specifications.
(3) In addition to the general assumptions of EN 1990 the following assumptions apply:
— the choice of the relevant design fire scenario is made by appropriate qualified and experienced
personnel, or is given by the relevant national regulation;
— any fire protection measure taken into account in the design will be adequately maintained.
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.
NOTE See the Bibliography for a list of other documents cited that are not normative references, including
those referenced as recommendations (i.e. through ‘should’ clauses) and permissions (i.e. through ‘may’ clauses).
EN 1090-2, Execution of steel structures and aluminium structures - Part 2: Technical requirements for steel
structures
EN 1090-4, Execution of steel structures and aluminium structures - Part 4: Technical requirements for cold-
formed structural steel elements and cold-formed structures for roof, ceiling, floor and wall applications
prEN 1990:2020, Eurocode - Basis of structural and geotechnical design
EN 1991 (all parts), Eurocode 1 - Actions on structures
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prEN 1993-1-2:2022 (E)
prEN 1991-1-2:2021, Eurocode 1 - Actions on structures - Part 1-2: Actions on structures exposed to
fire,
prEN 1993-1-1:2020, Eurocode 3 -Design of steel structures - Part 1-1: General rules: General rules and
rules for buildings
prEN 1993-1-3:2022, Eurocode 3 - Design of steel structures - Part 1-3: General rules: Supplementary rules
for cold formed steel members and sheeting
EN 1993-1-4, Eurocode 3 - Design of steel structures - Part 1-3: General rules: Supplementary rules for
stainless steels
prEN 1993-1-5:2022, Eurocode 3 - Design of steel structures - Part 1-5: Plated structural elements
EN 1993-1-6, Eurocode 3 - Design of steel structures - Part 1-6: Strength and Stability of Shell Structures
EN 1993-1-7, Eurocode 3 - Design of steel structures - Part 1-7: Plate assemblies with elements under
transverse loads
prEN 1993-1-8:2021, Eurocode 3 - Design of steel structures - Part 1-8: General rules: Design of joints
EN 1993-1-11, Eurocode 3 - Design of steel structures - Part 1-11: Design of structures with tension
components
EN 1993-1-13:2022, Eurocode 3 - Design of steel structures - Part 1-13: Beams with web openings
EN 1993-1-14, Eurocode 3 - Design of steel structures - Part 1-14: Design assisted by finite element analysis
3 Terms, definitions and symbols
Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1990, EN 1991-1-2 and the
following apply.
3.1.1
box value of section factor
ratio between the exposed surface area of a notional bounding box to the section and the volume of steel
3.1.2
critical temperature of structural steel element
temperature for a given load level, at which failure is expected to occur in a structural steel element
assuming a uniform temperature distribution
3.1.3
effective yield strength
stress level for a given temperature, at which the stress-strain relationship of steel is truncated to provide
a yield plateau
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3.1.4
fire protection material
any material or combination of materials applied to a structural member for the purpose of increasing its
fire resistance
3.1.5
part of structure
isolated part of a structure with appropriate support and boundary conditions
3.1.6
section factor
ratio between the exposed surface area and the volume of steel for a steel member, or ratio between the
internal surface area of the exposed encasement and the volume of steel for an enclosed member
Symbols
For the purposes of this document, the following symbols apply.
3.2.1 Latin upper case letters
A
i an elemental area of the cross-section with a temperature θ ;
i
2
A surface area exposed to fire of a member per unit length [m /m];
m
-1
Am / V section factor of unprotected steel members [m ];
2
A appropriate area of fire protection material per unit length of the member [m /m];
p
-1
A /V section factor for steel members insulated by fire protection material [m ];
p
C protection coefficient of member face i;
i
E modulus of elasticity of steel for normal temperature design;
a
E slope of the linear elastic range for steel at elevated temperature θ ;
a,θ a
Ed design effect of actions at normal temperature, determined in accordance with
EN 1991-1-1;
E design effect of actions for the fire situation, determined in accordance with
fi,d
prEN 1991-1-2, including the effects of thermal expansions and deformations;
E
p0,2,θ tangent modulus at 𝑓𝑓 ;
p0,2,θ
F design bearing resistance per bolt according to EN 1993-1-8;
b,Rd
F design bearing resistance per bolt in the fire situation at time t;
b,fi,t,Rd
F design shear resistance per bolt per shear plane calculated assuming that the
v,Rd
shear plane passes through the threads of the bolt according to EN 1993-1-8;
F design shear resistance per bolt per shear plane in the fire situation at time t;
v,fi,t, Rd
F design resistance per unit length of a fillet weld according to EN 1993-1-8;
w, Rd
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F design resistance per unit length of a fillet weld in the fire situation at time t;
w,fi,t, Rd
I radiative heat flux from an opening;
f
I radiative heat flux from a flame;
z
I radiative heat flux from a flame to a column face i;
z,i
L system length of a column in the relevant storey;
L length along axis between the opening and the relevant point;
i
M number of openings on side m;
M design buckling resistance moment in the fire situation at time t;
b,fi,t,Rd
M plastic moment resistance of the gross cross-section M for normal
c,Rd pl,Rd
temperature design; the elastic moment resistance of the gross cross-section
M for normal temperature design;
el,Rd
M elastic critical moment for lateral torsional buckling based on the gross cross-sectional
cr
properties, taking into account loading conditions, actual moment distribution and lateral
restraints;
M design moment resistance in the fire situation at time t;
fi,t,Rd
M design moment resistance of the cross-section for a uniform temperature θ ;
fi,θ,Rd a
N number of openings on side n;
N design buckling resistance in the fire situation at time t of a compression member;
b,fi,t,Rd
N elastic critical axial force for the relevant buckling mode based on the gross
cr
cross-sectional properties, using the buckling length under fire conditions;
N design resistance in the fire situation at time t of a tension member with a
fi,t,Rd
non-uniform temperature distribution across the cross-section;
N design resistance of a tension member with a uniform temperature θ ;
fi,θ,Rd a
N design tension resistance of the cross-section N for normal temperature design,
t,Rd pl,Rd
according to EN 1993-1-1;
R design resistance in the fire situation at time t;
fi,d,t
R value of R for time t = 0 ;
fi,d,0 fi,d,t
T temperature of fire [K];
f
T temperature of the steel member [K];
m
T flame temperature at the opening [K];
o
T flame temperature at the flame tip [813 K];
x
T flame temperature [K];
z
T flame temperature [K] from Annex B of prEN 1991-1-2:2021, level with the bottom of
z,1
a beam;
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oSIST prEN 1993-1-2:2022
prEN 1993-1-2:2022 (E)
T flame temperature [K] from Annex B of prEN 1991-1-2:2021, level with the top of
z,2
a beam;
V volume of a member per unit length;
V design value of the resistance to shear force for normal temperature design,
c,Rd
according to EN 1993-1-1;
V design shear resistance in the fire situation at time t;
fi,t,Rd
X characteristic value of a strength or deformation property (generally f or E )
k k k
for normal temperature design to EN 1993-1-1).
3.2.2 Latin lower case letters
a absorptivity of flames;
z
c specific heat of steel;
a
c specific heat of the fire protection material;
p
d effective cross-sectional dimension;
d cross-sectional dimension of member face i;
i
d thickness of fire protection material;
p
d thickness of the fire protection material. (d = 0 for unprotected members.);
f f
f
modification factor for χ ;
LT,fi
f proportional limit for steel at elevated temperature θ ;
p,θ a
ultimate strength at elevated temperature, allowing for strain-hardening;
f
u,θ
f yield strength at 20°C;
y
f effective yield strength of steel at elevated temperature θ ;
y,θ a
f nominal yield strength f for the elemental area A taken as positive on the
y,i y i
compression side of the plastic neutral axis and negative on the tension side;
h equivalent height of the opening;
eq
design value of the net heat flux per unit area;

h
net,d
h height of the top of the flame above the bottom of the beam;
z
i column face indicator (1), (2), (3) or (4);
reduction factor determined for the appropriate bolt temperature;
k
b, θ
k correction factor for moment distribution;
c
k reduction factor for the slope of the linear elastic range at the
E,θ
steel temperature θ reached at time t;
a
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oSIST prEN 1993-1-2:2022
prEN 1993-1-2:2022 (E)
reduction factor for the slope of the linear elastic range at the maximum steel
k
E,θ,com
temperature in the compression flange θ reached at time t ;
a,com
k reduction factor for the 0,2% proof strength at the steel
p0,2,θ
temperature θ reached at time t;
a
k correction factor for the shadow effect;
sh
k reduction factor for the ultimate strength at the steel temperature θ reached
u,θ a
at time t;

relative value of a strength or deformation property of steel at elevated
k
θ
temperature θ ;
a
k strength reduction factor for welds at elevated temperature;
w,θ
reduction factor for the yield strength at the steel
k
y,θ
temperature θ reached at time t ;
a
k reduction factor for the yield strength of steel at the maximum temperature in
y,θ,com
the compression flange θ reached at time t;
a,com
k reduction factor for the yield strength of steel at temperature θ ;
y,θ,i i
reduction factor for the yield strength of steel at the maximum steel
k
y,θ,max
temperature θ reached at time t ;
a,max
k reduction factor for the yield strength of steel at the steel temperature θ ;
y,θ,web web
k interaction factor for buckling about y-y axis;
y
k interaction factor for buckling about z-z axis;
z
k interaction factor for
...

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