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EN 1993-1-2 (2005) (English): Eurocode 3: Design of steel structures - Part 1-2: General rules - Structural fire design [Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC, Directive 2004/18/EC] EUROPEAN STANDARD EN 1993-1-2 NORME EUROPEENNE EUROpAISCHE NORM April 2005 ICS 13.220.50; 91.010.30; 91.080.10 Supersedes ENV 1993-1-2:1995 Incorporating Corrigendum December 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 Stahlbauten Regles generales -Calcul du comportement au feu -Teil 1-2: Allgemeine Regeln -Tragwerksbemessung fOr den Brandfall This European Standard was approved by CEN on 23 April 2004. 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. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists 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 Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COI'vlMITTEE FOR STANDARDIZATION COMITE EUROP DE NORl\lALISATION ROP.A.ISCHES KOMITEE FOR NORI'vlUNG Management Centre: rue de Stassart, 36 B-1050 Brussels © 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1993-1-2:2005: E worldwide for CEN national Members. BS EN 1993-1-2:2005 EN 1993-1-2:2005 (E) Contents Page Fore\vord ........................................................................................................................................................... 4 1. General ...................................................................................................................................................... 9 1.] Scope .................................................................................................................................................. 9 1.2 Norn1ative rcferences ........................................................................................................................ 10 1.3 Assun1ptions ..................................................................................................................................... 11 1.4 Distinction between principlcs and application mles ......................................................................... l1 1.5 TernlS and definitions ....................................................................................................................... 11 1.6 Synlbols ............................................................................................................................................ 12 2 Basis of desigll ......................................................................................................................................... 16 2. 1 Requ irenlcnts .................................................................................................................................... 16 2.1.1 Basic requirelllents ................................................................................................................... 16 2.] .2 Nominal fire exposure .............................................................................................................. 16 2. J .3 Paranletric fire exposure ........................................................................................................... 16 2.2 Actions .............................................................................................................................................. 17 2.3 Design values of material propcrties ................................................................................................ 17 2.4 Verification 111cthods ........................................................................................................................ 17 2.4.1 General ..................................................................................................................................... 17 2.4.2 Melnber analysis ....................................................................................................................... 18 2.4.3 Analysis of part of the stmcture ............................................................................................... 19 2.4.4 Global structural analysis ......................................................................................................... 20 3 Material properties ................................................................................................................................. 20 3.1 General ............................................................................................................................................. 20 3.2 Mechanical properties of carbon steels ............................................................................................ 20 3.2.] Strength and deformation propcrties ........................................................................................ 20 3.2.2 Unit 111ass .................................................................................................................................. 20 3.3 Mechanical properties of stainless stcels .......................................................................................... 23 3.4 Thernlal properties ............................................................................................................................ 23 3.4.1 Carbon steels ............................................................................................................................ 23 3.4.2 Stainless steels .......................................................................................................................... 26 3.4.3 Fire protection lnaterials ........................................................................................................... 26 4 Structural fire design ............................................................................................................................. 27 4.1. General ............................................................................................................................................. 27 4.2 Simple calculation models ................................................................................................................ 27 4.2. L General ..................................................................................................................................... 27 4.2.2 Classification of cross-sections ................................................................................................ 28 4.2.3 Resistance ................................................................................................................................. 28 4.2.4 Critical tel11perature .................................................................................................................. 36 4.2.5 Steel temperature development ................................................................................................ 37 4.3 Advanced calculation models .......................................................................................................... .43 4.3.] General ..................................................................................................................................... 43 4.3.2 Thernlal response ...................................................................................................................... 43 4.3.3 l\1echanical response ................................................................................................................. 43 4.3.4 Validation of advanced calculation models .............................................................................. 44 Annex A Inormative] Strain-hardening of carbon steel at elevated temperatures ............................... 45 Annex B [nonnative] Heat transfer to external steelwork .................................................................... .47 Annex C [inforlnativel Stainless steel ...................................................................................................... 65 Annex D linfornlative] Joints ................................................................................................................... 73 2 85 EN 1993 .. 1·2:2005 EN 1993-1-2:2005 (E) Annex E [informative] Class 4 cross-sections ......................................................................................... 76 3 BS EN 1993-1-2:2005 EN 1993 .. 1-2:2005 (E) Foreword This Europcan Standard EN 1993, EUfocode 3: Design of steel structurcs, has been prepared by Technical Committee CEN/TC250 « Structural Eurocodes », the Secretariat of which is held by BSI. CEN/TC250 is responsible for all Structural Eurocodcs. This European Standard shall be given the status of a National Standard, either by publication of an identical text or by endorsement, at the latest by October 2005, and cont1icting National Standards shall bc withdrawn at latest by March 20 10. This Eurocode supersedcs ENV 1993-1-2. According to thc CEN-CENELEC Intcrnal Regulations, the National Standard Organizations of thc following countries are bound to implement these European Standard: Austria, Belgium, Cyprus, Czech Republic, Dcnmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ircland, Italy, Latvia, Lithuania, Luxembourg, Malta, Nethcrlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Swedcn, Switzerland and United Kingdom. Background to the Eurocode programme In 1975, the Commission of thc European Community decided on an action programme in the field of construction, based on article 95 of the Treaty. The objective of the programme was the elimination of technical obstacles to trade and the harmonization of tcchnical specifications. Within this action programme, thc Commission took the initiative to establish a set of harmonized technical rules for the design of construction works which, in a first stage, would servc as an alternative to the national rules in force in thc l\1ember States and, ultimately, would replace them. For fifteen years, the Commission, with the help of a Steering Committee with Representatives of Membcr States, conducted the developmcnt of the Eurocodes programme, which led to thc first generation of Europcan codes in thc 1980s. In 1989, the Commission and the l\1ember Statcs of the EU and EFTA decided, on the basis of an agreement! bctwecn the Commission and to transfer the preparation and the publication of the Eurocodes to CEN through a series of Mandates, in order to provide them with a future status of European Standard (EN). This links de facto thc Eurocodes with the provisions of all the Council's Directives and/or Commission's Decisions dealing with European standards (e.g. the Council Directive 89/1 06/EEC on constl1Jction products - CPD - and Council Directives 93/37/EEC, 92/50/EEC and 89/440/EEC on public works and services and equivalent EFTA Directives initiated in pursuit of setting up the internal market). The Stmcturai Eurocode programme comprises the following standards generally consisting of a number of Parts: EN 1990 Eurocodc 0: Basis of Structural Design EN 1991 Eurocode 1: Actions on structurcs EN 1992 Eurocodc 2: Design of concrcte stmctures EN 1993 Eurocode 3: Design of stecl stmctures EN 1994 Eurocode 4: Design of composite steel and concrete structures EN 1995 Eurocode 5: Design of timber stmctures EN 1996 Eurocode 6: Design of masonry stmctures EN 1997 Eurocode 7: Geotechnical design EN 1998 Eurocode 8: Design of stmctures for earthquake resistance EN 1999 Eurocode 9: Design of aluminium structurcs 1 Agreement between the Commission of the European Communities and the European Committee for Standardisation (CEN) concerning the work on EUROCODES for the design of building and civil engineering works (BC/CEN/03/89). 4 BS EN 1993-1-2:2005 EN 1993-1-2:2005 (E) Eurocode standards recognize the responsibility of regulatory authorities in each Member State and have safeguarded their right to determine values related to regulatOlY matters at national level where these continue to ValY from State to State. Status and field of application of eurocodes The Member States of the EU and EFTA that Eurocodes serve as reference documents for the '·Ot"An,-.VJ'(,' following purposes: as a means to prove compliance of building and civil engineering works with the essential requirements of Council Directive particularly Essential Requirement N° I I'v1ccbanical resistance and stability and Essential Requirement N°2 - Safety in case of fire; as a basis for specifying contracts for construction works and related engineering as a framework for drawing up harmonized technical specifications for construction products (ENs and ETAs) The Eurocodes, as far as they concern the construction works themselves, have a direct relationship with the Interpretative Documents2 referred to in Article 12 of the CPD, although they are of a different nature from harmonized product standards3• Therefore, technical aspects arising from the Eurocodcs work need to bc adequately considered by CEN Technical Committees and/or EOTA Working Groups working on product standards with a view to achieving full compatibility of these technical specifications with the Eurocodes. The Eurocode standards provide common structural design rules for everyday use for the design of whole structures and component products of both a traditional and an innovative nature. Unusual forms of construction or design conditions are not specifically covered and additional expert consideration will be required by the designer in such cases. National Standards implementing Eurocodes The National Standards implementing Eurocodes will comprise the full text of the Eurocode (including any annexes), as published by CEN, which may be preceded by a National title page and National foreword, and may be followed by a National annex. The National annex may only contain information on those parameters which are left open in the Eurocode for national choice, known as Nationally Determined Parameters, to be used for the design of buildings and civil works to be constructed in the country concerned, i.e. : values and/or classes where alternatives arc given in the Eurocode, values to be used where a symbol only is given in the Eurocode, country data (geographical, climatic, etc.), e.g. snow map, the procedure to be used where alternative procedures are given in the Eurocode. It may contain decisions on the application of informative annexes, references to non-contradictory complementary information to assist the user to apply the Eurocodc. 2 According to Art. 3.3 of the CPD, the essential requirements (ERs) shall be given concrete form in interpretative documents for the creation of the necessary links between the essential requirements and the mandates for harmonized ENs and ET AGs/ET As. According to Art. 12 of the CPO the interpretative documents shall: a) give concrete form to the essential requirements by harmonizing the terminology and the technical bases and indicating classes or levels for each requirement where b) indicate methods these classes or levels of requirement with the technical methods or ccllcubtion and of proof, technical rules for etc, ; c) serve as a rcfercnce eSI[lbJI:;1111"lcnt of harmonized standards nnd guidelines lor European technical 8pprovals. or The Eurocodes, delacto, play simi lar role in the ficld the ER I and a part of ER 5 BS EN 1993-1-2:2005 EN 1993-1-2:2005 (E) Links between Eurocodes and harmonized technical specifications (ENs and ETAs) for products There is a need for consistency between the harmonized technical specifications for construction products and thc tcchnical rulcs for \vorks-+. Furthermore, all the information accompanying the CEMarking of the construction products \vhich refer to Eurocodes should clearly mention which Nationally Detel111ined Parametcrs have been taken into account. Additional information specific to EN 1993-1-2 EN 1993-) -2 describes the principles, requirements and rules for the structural design of steel buildings exposed to fire, including the following aspects. Safety requirements EN 1993-1-2 is intended for clients (e.g. for the formulation of their specific requirements), designers, contractors and relevant authorities. The general objectives of fire protection are to limit risks with respect to the individual and society, neighbouring property, and where required, environment or directly exposed property, in the case of fire. Construction Products Directive 8911 06/EEC gives the following essential requirement for the limitation of fire risks: "The construction works must be designed and build in such a way, that in the event of an outbreak of fire the load bearing resistance of the construction can be assumed for a specified period of time the generation and spread of fire and smoke within the works are limited the spread of fire to neighbouring construction works is limited the occupants can leave the works or can be rescued by other means the safety of rescue teams is taken into consideration". According to the Interpretative Document N° 2 "Safety in case of fire" the essential requirement may be observed by following various possibilities for fire safety strategies prevailing in the Member States like conventional fire scenarios (nominal fires) or "natural" (parametric) fire scenarios, including passive and/or active fire protection measures. The fire parts of Structural Eurocodes deal with specific aspects of passive fire protection in terms of designing structures and parts thereof for adequate load bearing resistance and for limiting fire spread as relevant. Required functions and levels of performance can be specified either in terms of nominal (standard) fire resistance rating, generally given in national fire regulations or by rcferring to fire safety engineering for assessing passive and active measures. Supplementary requirements concerning~ for example the possible installation and maintenance of sprinkler systems, conditions on occupancy of building or fire compartment, the use of approved insulation and coating materials, including their maintenance, are not given in this document, because they are subject to specification by the competent authority. Numerical values for partial factors and other reliability elements are given as recommended values that provide an acceptable level of reliability. They have been selected assuming that an appropriate level of workmanship and of quality management applies. 4 sec Art.3.3 and Arl.l2 of the CPO, as well as clauses 4.2, 4.3.1, 4,J.2 and 5.2 orIO I. 6 BS EN 1993-1-2:2005 EN 1993-1-2:2005 (E) Design procedures A full analytical procedure for structural fire design would take into account the behaviour of the structural at elevated temperatures, the potential heat exposure and the beneficial effects of active and passive fire protection systems, together with the uncertainties associated with these three features and the importancc of the structure (consequences of failure). At the present time it is possible to undertake a procedure for determining adequate performancc which incorporates some, if not all, of these parameters and to demonstrate that the structure, or its components, will give adequate performance in a real building fire. However, where the procedure is based on a nominal (standard) fire the classification system, which calJs for specific periods of fire resistance, takes illto account (though not explicitly), the features and uncertainties described above. Application of this Part 1-2 is illustrated in Figure 1. The prescriptive approach and the performance-based approach are identified. The prescriptive approach uses nominal fires to thermal actions. The performance-based approach, using fire safety engineering, refers to thermal actions based on physical and chemical parameters. For design according to this part, EN 1991-1-2 is required for the determination of thermal and mechanical actions to the structure. Design aids Where simple calculation models are not available, the Eurocode fire parts give design solutions in terms of tabulated data (based on tests or advanced calculation models), which may be used within the specified limits of validity. It is expected, that design aids based on the calculation models given in EN 1993-]-2, will be prepared by interested external organizations. The main text of EN 1993-1-2 together with normative Annexes includes most of the principal concepts and mles necessary for structural fire design of steel structures. National Annex for EN 1993-1-2 This standard gives altemative procedures, values and recommendations for classes with notes indicating where national choices may have to be made. Therefore the National Standard implementing EN 1993-1-2 should have a National annex containing all Nationally Determined Parameters to be used for the design of steel structures to be constmcted in the relevant countly. National choice is allowed in EN 1993-1-2 through paragraphs: 2.3 (1) 2.3 (2) 4.1 (2) 4.2.3.6 (1) 4.2.4 (2) 7 BS EN 1993-1-2:2005 EN 1993-1-2:2005 (E) I I Project Design I I I I I Prescriptive Rules Performance-Based Code (Thermal Actions given by Nominal Fire (Physically based Thermal Actions) I I I I I I I Member I I Analysis Part II Analysis of I Selectim of Simple or Advanced Analysis of the Structure Entire Structure Fire Development Models I I I I I I I Calculation of Calculation of Selection of Member Analysis of Analysis of Mechanical Actions Mechanical Actions Mechanical Analysis Part of the Entire at Boundaries at Boundaries Actions Structure Structure ........................ J I I I I I ] I I I I Tabulated Simple Advanced Simple Advanced Advanced Calculation of Calculation of Selection of Data Calculation Calculation Calculation Calculation Calculation Mechanical Mechanical Mechanical Models Models Models Models Models Actions Actions Actions (if available) at Boundaries at Boundaries I I I I I SimpleCalculation Advanced Advanced Advanced Models Calculation Calculation Calculation (if available) Models Models Models I Figure 0.1: Design procedure 8