FprEN 13381-11
(Main)Test methods for determining the contribution to the fire resistance of structural members - Part 11: Applied reactive protection to solid steel bars in tension based on mechanically loaded fire tests
Test methods for determining the contribution to the fire resistance of structural members - Part 11: Applied reactive protection to solid steel bars in tension based on mechanically loaded fire tests
This document describes the test and assessment procedure for determining the contribution of reactive fire protection systems to the fire resistance of solid steel bars used as tension members, when exposed to the standard temperature/time curve specified in EN 1363-1. In special circumstances, where specified in National Building Regulations, there can be a need to subject reactive fire protection systems to a slow heating curve (smouldering fire) as defined in EN 1363-2. The corresponding test and assessment procedure are described in Annex E. The fire protection performance is determined by testing mechanically loaded steel bars in horizontal orientation. Information regarding the testing of additional unloaded specimens is given to assess the influence of the bar orientation and smouldering fire behaviour.
The principles of the testing and assessment procedure can also be applied for other section shapes such as angles, channels and flats. This document does not include steel bars used as reinforcement in concrete construction.
The document is applicable to steel bars up to a maximum diameter of 130 mm. In the case of rectangular bars, the maximum edge length shall be limited to 130 mm with a maximum aspect ratio of 2:1 against the shorter edge length.
The test programme and the assessment are designed to cover:
- a range of valid fire protection classification periods;
- a range of thickness of the applied reactive fire protection system;
- a range of steel bar dimensions and profiles;
- a range of specified design temperatures;
- a range of load utilisation factors in case of fire;
- a range of bar orientation.
This document also provides the assessment procedure, which prescribes how the analysis of the test data shall be made and gives guidance on the procedures by which interpolation shall be undertaken. The assessment procedure is used to establish:
a) on the basis of data derived from mechanically loaded testing steel bar, any practical constraints on the use of the reactive fire protection system under fire test conditions (the physical performance);
b) on the basis of the temperature data derived from testing steel bar the thermal properties of the reactive fire protection system (the thermal performance).
The limits of applicability of the results of the assessment arising from the fire test are defined together with permitted direct application of the results to different steel types and sizes over the range of thicknesses of the applied reactive fire protection system tested.
Prüfverfahren zur Bestimmung des Beitrages zum Feuerwiderstand von tragenden Bauteilen - Teil 11: Brandschutzmaßnahmen für Stahl-Vollstäbe unter Zugbeanspruchung basierend auf einer Brandprüfung unter mechanischer Belastung
Dieses Dokument beschreibt das Prüf- und Beurteilungsverfahren für die Bestimmung des Beitrags reaktiver Brandschutzsysteme zum Feuerwiderstand geschlossener Stahlstäbe, die als Elemente unter Zugbeanspruchung verwendet werden, wenn sie der in EN 1363 1 festgelegten Norm-Temperatur/Zeitkurve ausgesetzt sind. Unter besonderen Umständen, soweit in der nationalen Bauordnung festgelegt, kann es erforderlich sein, ein reaktives Brandschutzsystem einer langsamen Erhitzungskurve (Schwelbrand) nach EN 1363 2 auszusetzen. Die entsprechenden Prüf- und Beurteilungsverfahren werden in Anhang E beschrieben. Das Brandschutzverhalten wird durch Prüfung mechanisch beanspruchter Stahlstäbe in horizontaler Ausrichtung geprüft. Informationen zur Prüfung zusätzlicher unbeanspruchter Probekörper werden bereitgestellt, um den Einfluss der Ausrichtung des Stabs und das Schwelbrandverhalten zu beurteilen.
Die Grundsätze des Prüf- und Beurteilungsverfahrens können außerdem auf andere Profilformen wie etwa Winkel, Kanäle und Flachstahl angewendet werden. Dieses Dokument beinhaltet keine Stahlstäbe, die in Betonkonstruktionen als Bewehrung eingesetzt werden.
Das Dokument ist auf Stahlstäbe mit einem maximalen Durchmesser von 130 mm anwendbar. Im Fall rechteckiger Stäbe ist die maximale Kantenlänge auf 130 mm beschränkt und das maximale Seitenverhältnis gegenüber der kürzeren Seitenlänge muss 2 : 1 betragen.
Das Prüfprogramm und die Beurteilung dienen dazu, Folgendes abzudecken:
- einen Bereich gültiger Brandschutzklassifizierungs-Zeitspannen;
- einen Dickebereich des angewendeten reaktiven Brandschutzsystems;
- einen Bereich von Maßen und Profilen des Stahlstabs;
- einen Bereich festgelegter Bemessungstemperaturen;
- einen Bereich von Auslastungsfaktoren im Brandfall;
- einen Bereich von Stabausrichtungen.
Dieses Dokument beschreibt auch ein Beurteilungsverfahren, das vorschreibt, wie die Analyse der Prüfdaten durchzuführen ist und bietet eine Anleitung zu den Verfahren für die Interpolation. Ziel des Beurteilungsverfahrens ist es:
a) mit Hilfe von durch Prüfung von mechanischen beanspruchten Stahlstäben ermittelten Prüfdaten Einschränkungen in der praktischen Anwendbarkeit des reaktiven Brandschutzsystems unter Brandbeanspruchung festzulegen (das physikalische Verhalten);
b) mit Hilfe von durch Prüfung von Stahlstäben ermittelten Temperaturmesswerten die thermischen Eigenschaften des reaktiven Brandschutzsystems zu bestimmen (thermische Leistungsfähigkeit).
Die Anwendungsgrenzen der aus Feuerprüfungen ermittelten Ergebnisse der Bewertung sowie die direkte Übertragbarkeit der Ergebnisse auf unterschiedliche Stahlarten und -größen für die verschiedenen Dicken des geprüften Brandschutzsystems werden festgelegt.
Méthodes d'essai pour déterminer la contribution à la résistance au feu des éléments de construction - Partie 11: Protection réactive appliquée aux barres d'acier pleines précontraintes (tirants) basé sur des essais de feu soumis à des contraintes mécaniques
Le présent document décrit le mode opératoire d'essai et d'évaluation permettant de déterminer la contribution des systèmes de protection réactive contre le feu à la résistance au feu des barres en acier pleines utilisées comme éléments précontraints, lorsqu'elles sont exposées à la courbe de température/temps normalisée spécifiée dans l'EN 1363 1. Dans des circonstances particulières, lorsque cela est spécifié dans le National Building Regulations (Règlement national du bâtiment), il peut être nécessaire de soumettre les systèmes de protection réactive contre le feu à une courbe d'échauffement lent (feu à combustion lente) telle que définie dans l'EN 1363 2. Le mode opératoire d'essai et d'évaluation correspondant est décrit à l'Annexe E. La performance de protection contre le feu est déterminée par l'essai des barres en acier soumises à une charge mécanique dans une direction horizontale. Des informations concernant l'essai d'éprouvettes supplémentaires non soumises à une charge sont données pour évaluer l'influence de la direction de la barre et le comportement du feu à combustion lente.
Les principes de la procédure d'essai et d'évaluation peuvent également être appliqués à d'autres formes de sections telles que cornières, profils U et plates. Le présent document n'inclut pas les barres en acier utilisées comme armatures dans les constructions en béton.
Le document s'applique aux barres en acier jusqu'à un diamètre maximal de 130 mm. Dans le cas des barres rectangulaires, la longueur maximale du bord est limitée à 130 mm avec un rapport d'aspect maximal de 2:1 par rapport à la longueur du bord la plus courte.
Le programme d'essai et l'évaluation sont conçus pour couvrir :
- une gamme de périodes de classification de la protection contre le feu valables ;
- une gamme d'épaisseurs du système de protection réactive contre le feu appliqué ;
- une gamme de dimensions et de profilés de barres en acier ;
- une gamme températures de calcul spécifiées ;
- une gamme de facteurs d'utilisation de la charge en cas d'incendie ;
- une gamme de direction de la barre.
Le présent document fournit également la procédure d'évaluation, qui prescrit la manière dont l'analyse des données d'essai est effectuée et donne des recommandations sur les procédures d'interpolation. La procédure d'évaluation est utilisée pour établir :
a) sur la base des données obtenues à partir d'une barre en acier d'essai soumise à une charge mécanique, toutes les contraintes pratiques liées à l'utilisation du système de protection réactive contre le feu dans les conditions de l'essai au feu (la performance physique) ;
b) sur la base des données de température obtenues à partir d'une barre en acier d'essai, les propriétés thermiques du système de protection réactive contre le feu (la performance thermique).
Les limites d'applicabilité des résultats de l'évaluation résultant de l'essai au feu sont définies de même que l'application directe autorisée des résultats à différents types et tailles d'acier dans la gamme d'épaisseurs du système de protection réactive contre le feu appliqué soumis à l'essai.
Preskusne metode za ugotavljanje prispevka k požarni odpornosti konstrukcijskih elementov - 11. del: Zaščita trdnih jeklenih palic v napetosti na podlagi požarnih preskusov z mehansko obremenitvijo
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2025
Preskusne metode za ugotavljanje prispevka k požarni odpornosti konstrukcijskih
elementov - 11. del: Zaščita trdnih jeklenih palic v napetosti na podlagi požarnih
preskusov z mehansko obremenitvijo
Test methods for determining the contribution to the fire resistance of structural members
- Part 11: Applied protection to solid steel bars in tension based on mechanically loaded
fire tests
Prüfverfahren zur Bestimmung des Beitrages zum Feuerwiderstand von tragenden
Bauteilen - Teil 11: Brandschutzmaßnahmen für Stahl-Vollstäbe unter
Zugbeanspruchung basierend auf einer Brandprüfung unter mechanischer Belastung
Méthodes d’essai pour la détermination de la contribution de la résistance au feu
d’éléments de construction - Partie 11 : Protection appliquée aux barres en acier pleines
précontraintes sur la base d'essais au feu soumis à une charge mécanique
Ta slovenski standard je istoveten z: prEN 13381-11
ICS:
13.220.50 Požarna odpornost Fire-resistance of building
gradbenih materialov in materials and elements
elementov
91.080.13 Jeklene konstrukcije Steel structures
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
prEN 13381-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2025
ICS 13.220.50
English Version
Test methods for determining the contribution to the fire
resistance of structural members - Part 11: Applied
protection to solid steel bars in tension based on
mechanically loaded fire tests
Méthodes d'essai pour la détermination de la Prüfverfahren zur Bestimmung des Beitrages zum
contribution de la résistance au feu d'éléments de Feuerwiderstand von tragenden Bauteilen - Teil 11:
construction - Partie 11 : Protection appliquée aux Brandschutzmaßnahmen für Stahl-Vollstäbe unter
barres en acier pleines précontraintes sur la base Zugbeanspruchung basierend auf einer Brandprüfung
d'essais au feu soumis à une charge mécanique unter mechanischer Belastung
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 127.
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, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 13381-11:2025 E
worldwide for CEN national Members.
prEN 13381-11:2025
Contents Page
European foreword . 5
Introduction . 6
1 Scope . 8
2 Normative references . 9
3 Terms, definitions, symbols and abbreviations . 9
3.1 Terms and definitions . 9
3.2 Symbols and abbreviations . 11
4 Test equipment . 13
4.1 General. 13
4.2 Furnace . 13
4.3 Load frame and hydraulic actuator . 14
5 Test programme . 14
5.1 General. 14
5.2 Mechanical loading conditions . 15
5.3 Number of specimens . 16
5.4 Size of specimens . 16
5.4.1 General. 16
5.4.2 Steel specification . 17
5.4.3 Surface treatment and application of the fire protection material . 17
5.5 Composition of reactive fire protection system . 18
5.5.1 General. 18
5.5.2 Thickness of applied reactive fire protection system . 18
5.6 Selection of specimens . 20
6 Installation of the specimens . 21
6.1 Specimen installation patterns . 21
6.2 Installation of the steel bars . 21
6.3 Furnace load . 22
6.4 Mechanical tensile load . 22
7 Conditioning of the specimens . 22
8 Application of instrumentation . 22
8.1 General. 22
8.2 Instrumentation for the measurement of test load and deformation . 22
8.3 Instrumentation for measurement and control of the furnace temperature . 23
8.3.1 General. 23
8.3.2 Furnace temperature . 23
8.4 Instrumentation for the measurement of the steel temperature . 24
8.5 Instrumentation for furnace pressure measurement . 27
8.5.1 General. 27
8.5.2 Establishing of the nominal pressure plane . 27
9 Test procedure . 27
9.1 General. 27
9.2 Furnace temperature and pressure . 27
9.3 Temperature of the specimen . 27
prEN 13381-11:2025
9.4 Deformation of the specimen . 27
9.5 Observations . 27
9.6 Termination of test . 28
10 Test results. 28
10.1 Acceptability of test results. 28
10.2 Presentation of test results in the test report . 28
11 Assessment . 29
11.1 General . 29
11.2 Preparation of experimental data obtained in the fire tests . 30
11.3 Performance . 35
11.3.1 Thermal performance . 35
11.3.2 Physical performance . 35
11.4 Assessment procedure. 37
11.5 Interpolation procedure limits . 39
12 Method to transfer results between Influence of different steel bar orientations . 39
12.1 General . 39
12.2 Experimental setup for an unloaded fire test . 39
12.3 Correction due to different thicknesses of the reactive fire protection system . 42
12.4 Evaluation of the test data . 44
13 Application of the test and assessment results to different profile types. 44
14 Report of the assessment . 45
15 Limits of the applicability of the results of the assessment . 46
Annex A (informative) Example of different test sets and the resulting scope of application
based on the assessment . 48
A.1 General . 48
A.2 Examples of test sets . 48
A.2.1 General . 48
A.2.2 Description of the test set with one tested steel bar . 48
A.2.3 Description of the test set with three tested steel bars . 49
Annex B (informative) Example of an assessment . 52
B.1 General . 52
B.2 Definition of the intended scope of application by the manufacturer . 52
B.3 Preparation of experimental data obtained in the fire tests . 54
B.4 Performance . 55
B.5 Results of the mechanically loaded fire tests . 56
B.6 Result of the assessment . 58
Annex C (normative) Linear interpolation analysis. 60
C.1 General . 60
C.2 Examples of interpolation methods containing only specimens which were not
excluded from the assessment . 60
C.2.1 Assessment of interpolation procedure limits . 60
C.2.2 Interpolation based on steel bar diameter (D) . 62
prEN 13381-11:2025
C.2.3 Interpolation based on the design temperature (θ ) . 66
i
C.2.4 Interpolation based on the load utilization factor . 69
C.3 Interpolation methods to consider values which were excluded from the assessment
................................................................................................................................................................... 72
C.3.1 Interpolation based on the load utilization factor . 72
Annex D (informative) Example of the procedure to consider the influence of the bar
orientation on the thermal performance of reactive fire protection system . 78
D.1 General. 78
D.2 Results from additional fire test with eight unloaded steel bars . 78
Annex E (normative) Test method to the slow heating curve (smouldering fire) . 83
E.1 General. 83
E.2 Test equipment . 83
E.3 Test specimen . 83
E.4 Termination of test . 83
E.5 Assessment of the results. 84
Bibliography . 85
prEN 13381-11:2025
European foreword
This document (prEN 13381-11:2024) has been prepared by Working Group 1 ‘Structural and separating
elements’ under Technical Committee CEN/TC 127 “Fire safety in buildings”, the secretariat of which is
held by BSI.
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
This document is one of a series of standards for evaluating the contribution to the fire resistance of
structural members by applied fire protection materials. Other parts of this series are:
Part 1: Horizontal protective members.
Part 2: Vertical protective members.
Part 3: Applied protection to concrete members.
Part 4: Applied passive protection to steel members.
Part 5: Applied protection to concrete/profile sheet steel and composite members.
Part 6: Applied protection to concrete filled hollow steel columns.
Part 7: Applied protection to timber members.
Part 8: Applied reactive protection to steel members.
Part 9: Applied fire protection systems to steel beams with web openings.
Part 10: Applied protection to solid steel bar in tension.
prEN 13381-11:2025
Introduction
The evaluation of a system's capability to provide fire protection performance to beams and/or columns
with I- or H-section as well as hollow section is undertaken by test and assessment procedures detailed
in EN 13381-8 for reactive (intumescent) fire protection systems. The scope of the above standard
excludes the assessment of solid steel bars used as tension members.
In general, it is not possible to use the results of fire protection systems tested according to EN 13381-8
on beams or columns with open or closed profile to steel tension bars with solid section. This has several
reasons:
a) the profiles used for steel bars are usually much slenderer than the profiles used for beams or
columns. Consequently, to achieve the same fire resistance usually higher thicknesses of the reactive
fire protection system are required;
b) due to the different profile shape, there is an altered foaming and cracking behaviour of reactive fire
protection systems. On the predominantly flat surfaces of a beam with open profile, reactive fire
protection systems behave differently than on highly convex curved surface of steel bars with
circular solid section;
c) because the tensile stresses in a steel bar are equal along the entire bar length and within the cross-
section, the failure occurs at the position, where the highest steel temperature is present. Therefore,
tensile bars are vulnerable to local defects, e.g. cracks or ununiform foam thicknesses of reactive fire
protection systems. Furthermore, beams have the possibility of cross-sectional plasticisation. Due to
the resulting stress redistribution and the activation of additional load capacity reserves, in fire tests
beams suffer lower strains compared to a bar in pure tension. This is also clear from the fact that the
tests of a steel bar usually end with the breakage. In mechanically loaded beam tests such a high
strain is usually not achieved;
d) columns are not suitable for a comparison with steel bars, because the cross-sections are much
bigger as well as the thermal and mechanical strains are acting in opposite direction;
e) in contrast to beams, which are generally used in a horizontal position, steel bars are used in different
orientations. This may influence the thermal protection performance of the reactive fire protection
system.
For reactive fire protection systems that have already been successfully tested and assessed according to
EN 13381-8, the test standard EN 13381-10 offers under certain conditions the possibility to extend the
scope of application to steel tension bars with solid sections. The fire tests in EN 13381-10 are based
upon unloaded specimens. Because this approach contradicts to the German national safety level, where
the fire resistance of structural members must be tested under mechanical load, an A-Deviation was
granted, meaning that it is not possible to apply EN 13381-10 in Germany. In addition, recent research
and testing on loaded and unloaded steel bars protected with reactive fire protection coatings has shown
the need for mechanically loaded fire testing.
prEN 13381-11:2025
The following standard provides a test and assessment procedure to cover a reactive fire protection
system's scope of application to solid circular or rectangular steel bars used as tension members based
on mechanically loaded fire tests. The standard is a stand-alone test standard and does not require a
successful completion of the test procedure according to EN 13381-8. The standard has been created to
cover a testing and assessment procedure based primarily upon mechanically loaded fire tests. Across a
range of solid circular and/or rectangular bars fire tests on mechanically loaded specimens are carried
out. Unloaded specimens may be used to assess additional aspects, such as the influence of the bar
orientation as well as smouldering fire behaviour. The assessment procedure described in this document
aims to determine the reactive fire protection system's thermal protection performance.
The document does not apply to passive fire protection systems.
prEN 13381-11:2025
1 Scope
This document describes the test and assessment procedure for determining the contribution of reactive
fire protection systems to the fire resistance of solid steel bars used as tension members, when exposed
to the standard temperature/time curve specified in EN 1363-1. In special circumstances, where
specified in National Building Regulations, there can be a need to subject reactive fire protection systems
to a slow heating curve (smouldering fire) as defined in EN 1363-2. The corresponding test and
assessment procedure are described in Annex E. The fire protection performance is determined by
testing mechanically loaded steel bars in horizontal orientation. Information regarding the testing of
additional unloaded specimens is given to assess the influence of the bar orientation and smouldering
fire behaviour.
The principles of the testing and assessment procedure can also be applied for other section shapes such
as angles, channels and flats. This document does not include steel bars used as reinforcement in concrete
construction.
The document is applicable to steel bars up to a maximum diameter of 130 mm. In the case of rectangular
bars, the maximum edge length is limited to 130 mm with a maximum aspect ratio of 2:1 against the
shorter edge length.
The test programme and the assessment are designed to cover:
— a range of valid fire protection classification periods;
— a range of thickness of the applied reactive fire protection system;
— a range of steel bar dimensions and profiles;
— a range of specified design temperatures;
— a range of load utilization factors in case of fire;
— a range of bar orientation.
This document also provides the assessment procedure, which prescribes how the analysis of the test
data is made and gives guidance on the procedures by which interpolation is undertaken. The assessment
procedure is used to establish:
a) on the basis of data derived from mechanically loaded testing steel bar, any practical constraints on
the use of the reactive fire protection system under fire test conditions (the physical performance);
b) on the basis of the temperature data derived from testing steel bar the thermal properties of the
reactive fire protection system (the thermal performance).
The limits of applicability of the results of the assessment arising from the fire test are defined together
with permitted direct application of the results to different steel types and sizes over the range of
thicknesses of the applied reactive fire protection system tested.
prEN 13381-11:2025
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.
EAD 350402-00-1106, Reactive coatings for fire protection of steel elements
EN 1363-1:2020, Fire resistance tests — Part 1: General requirements
EN 1363-2, Fire resistance tests — Part 2: Alternative and additional procedures
EN 10025-1, Hot rolled products of structural steels — Part 1: General technical delivery conditions
EN ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature (ISO
6892-1)
EN 10204, Metallic products — Types of inspection documents
EN ISO 13943, Fire safety — Vocabulary
EN ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part
1: Tension/compression testing machines — Calibration and verification of the force-measuring system (ISO
7500-1)
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1363-1, EN ISO 13943 and
ISO 8421-2, and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1.1
steel bar
element of building construction, which is loadbearing and fabricated from steel. It has a solid circular or
rectangular (including square) cross-section composed entirely of steel with a consistent cross-sectional
size throughout its length
3.1.2
reactive fire protection material
reactive materials which are specifically formulated to provide a chemical reaction upon heating such
that their physical form changes and in doing so provide fire protection by thermal insulative and cooling
effects
3.1.3
fire protection system
fire protection material together with any supporting system including mesh reinforcement and a
specified primer and top coat if applicable
prEN 13381-11:2025
3.1.4
fire protection
protection afforded to the steel member by the reactive fire protection system such that the temperature
of the steel member is limited throughout the period of exposure to fire
3.1.5
test specimen
steel bar plus the reactive fire protection system under test
3.1.6
fire protection thickness
mean dry film thickness of the reactive fire protection material excluding primer and top coat
3.1.7
stickability
ability of a reactive fire protection system to remain sufficiently coherent and in position for a well-
defined range of deformations, furnace and steel temperatures, such that its ability to provide fire
protection is not significantly impaired
3.1.8
maximum steel temperature
the highest average temperature recorded at two measuring stations nearest the rupture point
3.1.9
section factor
ratio of the fire exposed outer perimeter area of the steel bar per unit length, to its cross-sectional volume
per unit length
3.1.10
mechanical load
axial tensile force applied to the mechanically loaded specimen during the fire test (see 6.4)
3.1.11
load utilisation in case of fire
ratio of mechanical load to the tensile load carrying capacity of steel bar in case of fire (see 6.4)
3.1.12
test programme
describes the intended scope of application (see Clause 5)
3.1.13
test set
part of the test programme and consists of a group of mechanically loaded specimens (template see 5.6)
3.1.14
design steel bar temperature
temperature of a steel bar, which shall be used for the assessment of the physical and thermal
performance
3.1.15
deformation steel bar temperature
temperature of a steel bar, which shall be used by the structural engineer to check the total deformation
of the steel bar and the entire steel construction at elevated temperature
prEN 13381-11:2025
3.2 Symbols and abbreviations
For the purposes of this document, the following symbols and abbreviations apply.
Symbol Unit Description
-1
α thermal expansion coefficient
K
A /V -1
Section factor of the unprotected steel section
m m
A
mm Cross-sectional area of the steel section
section
b mm Width of the rectangular solid steel section
D mm Diameter of the circular solid steel section
d
mm Thickness of reactive fire protection system
p
minimum protection thickness of the loaded or tall section
d
mm
min
(according to EN 13381-8)
maximum protection thickness of the loaded or tall section
d
mm
max
(according to EN 13381-8)
D
mm Diameter of the smaller tested steel bar from the fire test
small
D
mm Diameter of the larger tested steel bar from the fire test
large
Diameter of steel bar for which appropriate dry film thickness is
D
mm
select
calculated
Mean value of all thickness measurements of the fire protection
DFT
mm
mean
material
DFT
mm Dry film thickness of the smaller tested steel bar from the fire test
small
DFT
mm Dry film thickness of the larger tested steel bar from the fire test
large
Dry film thickness of the unloaded steel bar used as reference
DFT
Mm
ref
specimen
DFT of the unloaded steel bar for which the correction time
mean
DFT
mm
K
(t ) is calculated
corection,k,i
-1
ė Strain rate of steel
min
F
kN The mechanical tensile load applied to the specimen
load
f
N/mm Yield strength at room temperature
y,20°C
f 2
N/mm 0,2 % proof stress at room temperature
p0.2,20°C
h mm Height of the rectangular steel section
L
mm Fire exposed length of the mechanically loaded specimen
F
L
mm Total length of the mechanically loaded specimen
G
L
mm Total length of unloaded steel bar
U
r mm Radius of the circular solid steel section
prEN 13381-11:2025
s mm Cross-sectional dimension of the specimen
Design steel temperature for the thermal and physical
θ
°C
i
assessment
Steel deformation temperature for the check of the total
θ
°C deformation of the steel bar and the entire steel construction at
def
elevated temperature
θ Maximum steel temperature at time t
°C
s i
θ
°C Steel temperature when the rupture occurred
rupture
Selected design temperature value for which the dry film
θ
°C
select
thickness will be calculated
Average temperature of unloaded steel bar for different
θ
°C
average,unload,i
orientation
Average temperature of unloaded specimen in different
θ
°C orientation for bars exposed to slow heating (SH)
SH,average,unload,i
temperature/time curve
Temperature difference between steel bars with different
Δθ
°C
k
orientation
t min Fire performance period
t
min Fire resistance time
F
t The time when the load-bearing capacity (t ) is reached
min
C C
Time for which the load utilisation factor in case of fire is
t
min
C,i
calculated for interpolation purposes
Corrected time, when unloaded steel bar reached design
t
min
correction,k,i
temperature θ
i
t min Time for the reference section to reach the design temperature
k,i
t min
Time when the steel bar rupture occurred
rupture
Temperature difference between unloaded steel bars with
ΔT
°C
unload,i
different orientations
Temperature difference between loaded steel bars with different
ΔT
°C
load,k
orientations
U mm Deformation of the steel bar including longitudinal elongation
dU/dt mm/min Rate of deformation
Limit value of the rate of deformation of the mechanically loaded
ΔdU/dt
mm/min
limit
specimen
μ
‒ Load utilisation factor at ambient temperature
µ
‒ Load utilisation factor in case of fire
fi
µ
‒ Upper limit of load utilisation factor in case of fire
fi,max
µ
‒ Lower limit of load utilisation factor in case of fire
fi,min
prEN 13381-11:2025
Load utilisation factor in case of fire, which is selected based on
µ
‒
fi,select
the applied load utilisation in case of fire of tension steel bar
Load utilisation factor in case of fire, which is reduced based on
µ
‒
fi,reduce
the real load utilisation of tension steel bars
Abbreviation Description
DFT Dry film thickness of the reactive fire protection system
MS Measuring station
MP Measuring point
TC Thermocouple
ULS Ultimate limit state
4 Test equipment
4.1 General
The furnace and test equipment shall conform to that specified in EN 1363-1. A number of steel bars,
protected by the reactive fire protection system, are mechanically loaded by a constant tension load and
then heated in a furnace according to the protocol given in EN 1363-1. It is recommended that the tests
be continued until the specimen reaches the maximum steel temperature specified in the scope of testing
or rupture of the specimen occurs. The description in this document refers to a fire test in horizontal
position of the bar. However, it is also possible to conduct the fire test in vertical position. The load device
and the furnace shall be changed accordingly. The procedures given in EN 1363-1 shall be followed in the
performance of this test unless specific contrary instructions are given in this document. The specimens
shall be chosen to suit the scope of testing.
4.2 Furnace
The furnace shall permit the dimensions of the test specimens to be exposed to heating, as specified in
Clause 5 and their installation within the test furnace to be as specified in Clause 6. A minimum distance
of 300 mm shall be kept between the specimen and the edge of the burner outlet, the burner flame, other
obstacles (except furnace plate thermocouples and specimen thermocouples) and furnace walls, floor
and ceiling (see 6.1 and Figure 1). In addition, a direct impingement shall be avoided. In General, the
furnace shall be able to create a uniform temperature distribution around the specimen. Furthermore,
the required furnace temperature shall be reached at the specimen and the associated plate
thermocouples.
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Key
1 undisturbed and obstacle free zone
2 specimen (tension bar)
3 = 300 mm
4 fire exposed length of the specimen (L = 1 000 mm)
F
Figure 1 — Undisturbed and obstacle free zone around the specimen in the furnace
(the geometric limitations also apply to other bar orientations)
4.3 Load frame and hydraulic actuator
The loading equipment shall be capable of subjecting the test specimens to the level of tensile load
specified in the scope of testing (see 5.1). Furthermore, the loading equipment shall be able to simulate
conditions of uniform loading, which can maintain the test load at a constant value (±2 % of the required
value, according to EN ISO 7500-1) without changing its distribution and following the maximum
deformation as well as rate of deformation of the test specimen until failure (maximum temperature or
rupture of the bar) occurs.
The load frame shall have room temperature over the entire duration of the fire test (a locally higher
temperature of the load frame of not more than 50 K is allowed; it is recommended to locate the load
frame outside of the furnace). The effect of deformation of the load frame shall be considered to
determine the steel rods deformation. A computer-based controlling of the loading system and
deformation measurement is recommended.
5 Test programme
5.1 General
The manufacturer of the reactive fire protection system specifies the intended scope of application by
defining the test programme. To develop the test programme the testing institute can be consulted. Based
on the selected test programme the different test sets can be defined. The test programme contains at
least one test set. If the general parameters selected in the test programme have more than one entry per
line, several test sets shall be created. A subdivision into different test sets is required, because in the
assessment only specimens with comparable parameters, i.e. identical entries for the general parameters,
can be assessed together. In general, it is possible to include the data of one specimen for different test
sets. A change or extension of a test set is possible by changing or adding new values for a variable
parameter. For the variable parameter a range can be specified. A change of the variable parameters does
prEN 13381-11:2025
not require a new test set. Recommendations and details for the selection of the specimens of a test set
are given in 5.6. The following scheme describes in Table 1 the general structure of a test programme for
mechanically loaded specimens.
Table 1 — Test programme to specify the intended scope of application of the reactive fire
protection system
Examples (If more than one entry per line
General parameter:
is selected several test sets are required)
1) Reactive fire protection material Name of the product
2) Fire resistance class R30, R60, R90, …
3) Steel type Hot-rolled steel; cold-formed steel
4) Steel grade S designation (S235; S275; S355; S420; S460)
5) Profile type Circular; rectangular (including square)
6) Orientation of the loaded bar Horizontal; inclined; vertical
7) Load utilization factor in case of fire µ ≤ 0,65 (fully loaded steel bar); µ ≤ 0,60, …
fi fi
8) Fire exposed length of the steel bar L
F
Examples (In each line a range has to be
Variable parameter:
defined)
8) Steel temperature range for thermal
θ (min., int., max.), e.g.: (350, 400, …, 750 °C)
i
assessment purpose (design temperature)
Section factor and cross-sectional dimension:
9) Steel bar dimension
(min., int., max.)
10) Thickness of reactive fire protection
d (min., int., max.)
p
system
The aim of the information addressed in the test programme is to set an intended scope of application for
the reactive fire protection system. The amount of testing influences the assessment and limits the final
scope of application for the product. Generally, an increase of the intended scope of application or an
increase of the gradations of the defined parameters requires a more extensive test programme, i.e.
higher number of test sets. However, in many cases the final scope of application of the tested reactive
fire protection system could be larger than specified in the test programme. All permitted direct
extensions are given in Clause 15.
5.2 Mechanical loading conditions
The mechanically loaded steel bars shall be oriented horizontally within the furnace. Each end of the bar
shall be connected to the load device, which consist of a load frame and a hydraulic actuator. For this
purpose, a sample holder designed for transferring tensile forces shall be provided. The connections
between the specimen and the loading device shall be located outside the furnace. The penetration of the
specimen through the furnace walls shall be designed in such a way that the reactive fire protection
system does not peel off the specimen during the fire test. For this purpose, a moveable insulation, which
is attached to the specimen, is recommended. A proposal of the basic structure of the load device to
perform mechanically loaded fire tests on steel bars with reactive fire protection system is given in
Figure 2.
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Key
1 fire exposed length of the specimen (L = 1 000 mm)
F
2 furnace interior
3 furnace wall with opening for passing the specimen
4 specimen (steel bar)
5 movable insulation (attached to the specimen)
6 tensile force
7 hinged connection of the specimen to the load frame (none movable end)
8 hinged connection of the specimen to the hydraulic actuator (movable end)
Figure 2 — Schematic drawing of the basic structure of the load device and the furnace
5.3 Number of specimens
The number of specimens depends on the scope of testing (see 5.1 and 5.6). The specimens shall be tested
with mechanical tensile load. Since the loaded tests are usually only performed in one bar orientation, i.e.
horizontally, additional unloaded specimens can be tested to assess the influence of other bar
orientations and thus to increase the intended scope of application (see Clause 12).
5.4 Size of specimens
5.4.1 General
The cross-section of the steel bar is characterized by the profile type, the largest cross-sectional
dimension (s) and the section factor (A /V). The steel bar can have a rectangular (including square) or
m
circular shape (see Figure 3). The size of rectangular solid bars is defined by the width (b) and the height
(h). The height of rectangular bars shall be always larger than the width. For circular solid bars the
radius (r) or the diameter (D) characterizes the size of the cross-section. The largest cross-sectional
dimension of a specimen is equal to the height of a rectangular bar or the diameter of a circular bar. The
section factor is the ratio of the fire exposed outer perimeter area of the steel bar per unit length to its
cross-sectional volume per unit length.
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Key
Left rectangular bar (h ≥ b)
Middle square bar
Right circular bar
1 h ≥ b
2 height (h)
3 width (b)
4 Square bar (h = b)
5 radius (r)
6 diameter (D)
Figure 3 — Possible profile types (cross-sectional shapes of a steel bar to be tested)
The length of th
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