EN 1993-1-4:2025/prA1

• Abstract:

  1.1 Scope of prEN 1993-1-4; This document provides supplementary rules for the structural design of steel structures that extend and modify the application of EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8 to austenitic, duplex (austenitic-ferritic) and ferritic stainless steels.; NOTE 1 Austenitic-ferritic stainless steels are commonly known as duplex stainless steels. The term duplex stainless steel is used in this document.; NOTE 2 Information on the durability of stainless steels is given in Annex A.; NOTE 3 The execution of stainless steel structures is covered in EN 1090-2 and EN 1090-4.; 1.2 Assumptions; Unless specifically stated, EN 1990, EN 1991 (all parts), EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8 apply.; The design methods given in prEN 1993-1-4 are applicable if; - the execution quality is as specified in EN 1090-2 and EN 1090-4, and; - the construction materials and products used are as specified in EN 1993-1-1, EN 1993-1-3, EN 1993 1-5 and EN 1993-1-8, or in the relevant material and product specifications.

• Status: Not Published
• Publication Date: 22-Jul-2027
• ICS: 91.010.30 - Technical aspects
• ICS: 91.080.13 - Steel structures
• Technical Committee: CEN/TC 250 - Structural Eurocodes
• Drafting Committee: CEN/TC 250/SC 3/WG 4 - Evolution of EN 1993-1-4 - Stainless stee
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 20-Aug-2026
• Due Date: 14-Sep-2026
• Completion Date: 20-Aug-2026
• Ref Project: SIST EN 1993-1-4:2025/oprA1:2026 - Eurocode 3 - Design of steel structures - Part 1-4: Stainless steel structures

• Amends: EN 1993-1-4:2025 - Eurocode 3 - Design of steel structures - Part 1-4: Stainless steel structures
• Effective Date: 20-Jan-2026

EN 1993-1-4:2025/prA1 is a CEN draft amendment to Eurocode 3, Part 1-4 for stainless steel structures. It updates the design rules for austenitic, duplex and ferritic stainless steels, mainly for structural analysis, connections, material classification and durability. It is aimed at engineers, fabricators and reviewers who use Eurocode 3 for stainless steel projects.

What does EN 1993-1-4:2025/prA1 specify?

EN 1993-1-4:2025/prA1 specifies supplementary rules for stainless steel structures that extend and modify the use of EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8. The scope covers austenitic, duplex (austenitic-ferritic) and ferritic stainless steels, and Annex A addresses durability.

The amendment is organized as changes to the whole document, the Introduction, Clauses 3, 5, 7, 8 and 10, and Annex A.

Section	What it covers
Whole document	Reference updates and editorial alignment
Clause 3	Terms, definitions and symbols
Clause 5	Materials
Clause 7	Structural analysis
Clause 8	Ultimate limit states
Clause 10	Connection design
Annex A	Selection of materials and durability

What are the key requirements of EN 1993-1-4:2025/prA1?

EN 1993-1-4:2025/prA1 keeps the Eurocode approach: the design rules work together with EN 1990, EN 1991, EN 1993-1-1, EN 1993-1-3, EN 1993-1-5 and EN 1993-1-8 unless the part says otherwise. In practice, that means the stainless steel rules are not standalone - the designer also has to follow the general Eurocode basis, the applied actions and the relevant execution and product specifications.

Structural analysis and stability

Clause 7 clarifies the use of slenderness, including the symbol λ in second-order effects and in the amplitude of imperfection for elastic critical buckling modes. This matters because stability checks must use the right slenderness definition and the right National Annex choice where one exists.

Clause 8 adds a nationally determined value for η in shear buckling resistance. For design work, that means the shear-buckling check is not fully fixed at European level and the National Annex has to be checked before the calculation is finalized.

Connections and preload

Clause 10 updates bolt preload wording and allows the National Annex to permit higher preload levels up to 0.7 fubAs. In practice, connection design must follow the nationally chosen preload limit, not just the general formula.

Clause 5 also changes the wording on bolt tightening qualification procedure and on corrosion resistance of filler material. The practical effect is that bolting procedures and welding consumables have to match the corrosion performance expected for the base material and joint.

Materials and durability

Annex A adds a route for stainless steel grades not listed in Table A.3 to be classified in a corrosion resistance class, provided the grade is listed in EN 10088 and passes a monitored exposure trial. The trial uses defined environmental conditions, specified surface finishes and a reference panel, so the designer or specifier has a method to justify new grades instead of relying only on the existing table.

The amendment also ties durability classification to visible corrosion and staining performance. That helps buyers and material specifiers decide whether a grade can be accepted for the intended exposure environment.

What terms does EN 1993-1-4:2025/prA1 define?

EN 1993-1-4:2025/prA1 defines several terms and symbols used in the design rules and material classification.

• Austenitic stainless steels - one of the stainless steel families covered by this part of Eurocode 3.
• Duplex stainless steels - the term used in the document for austenitic-ferritic stainless steels.
• Ferritic stainless steels - the third stainless steel family covered by the scope.
• CRC - corrosion resistance class, used in Annex A and Table A.3 to group grades by durability performance.
• εfl - strain induced in the flat faces of rectangular hollow sections during section forming.
• εf - elongation after fracture as defined in the product standard.
• National Annex - the national Eurocode document that can set certain values, such as η or the allowable preload level.

Who uses EN 1993-1-4:2025/prA1?

EN 1993-1-4:2025/prA1 is used by structural engineers, calculation teams and checking engineers who design stainless steel members, plates and joints to Eurocode 3. It is also used by fabricators and execution planners because the design assumptions depend on the execution standards EN 1090-2 and EN 1090-4.

Material suppliers, quality managers and buyers use it when choosing stainless steel grades, surface finishes and corrosion resistance classes. Specifiers use it to state the required stainless steel family and to coordinate any National Annex-dependent design values.

What changed in EN 1993-1-4:2025/prA1 from the previous edition?

EN 1993-1-4:2025/prA1 amends EN 1993-1-4:2025. The foreword says some changes are editorial, and the main technical changes are:

• clarification of λ in second-order effects and replacement of λ in the imperfection formula for elastic critical buckling modes;
• addition of a nationally determined parameter for η in shear buckling resistance;
• permission for preload levels up to 0.7 fubAs where the National Annex allows it;
• new rules for classifying stainless steel grades not listed in Table A.3 by corrosion resistance class.

Which standards are used with EN 1993-1-4:2025/prA1?

Standard	What it contributes
EN 1990	Basis of structural and geotechnical design
EN 1991 (all parts)	Actions on structures
EN 1993-1-1	General rules and rules for buildings
EN 1993-1-3	Cold-formed members and sheeting
EN 1993-1-5	Plated structural elements
EN 1993-1-8	Joints
EN 1090-2	Execution of steel structures
EN 1090-4	Execution rules used with stainless steel structures
EN 10088	Stainless steel grades used for material selection in Annex A
EN 10088-2	Surface finishes and product conditions used in the Annex A exposure trial

What does the EN 1993-1-4:2025/prA1 document contain?

EN 1993-1-4:2025/prA1 contains amendment text rather than a full rewritten standard. It updates clauses on terms and symbols, materials, structural analysis, ultimate limit states and connection design, and it revises Annex A on selection of materials and durability.

The document also updates references, notes and formula-related text that affect buckling checks, bolt preload design and corrosion classification. Annex A adds the monitored exposure trial method for qualifying stainless steel grades not already listed in Table A.3.

For design and review work, the most useful parts are the clause-by-clause modifications and the annex provisions that tell users how to justify a grade, a preload level or a stability calculation under the Eurocode system.

SLOVENSKI STANDARD
01-julij-2026
Evrokod 3 - Projektiranje jeklenih konstrukcij - 1-4. del: Nerjavne jeklene
konstrukcije
Eurocode 3 - Design of steel structures - Part 1-4: Stainless steel structures
Eurocode 3 - Bemessung und Konstruktion von Stahlbauten - Teil 1-4: Tragwerke aus
nichtrostenden Stählen
Eurocode 3 - Calcul des structures en acier - Partie 1-4 : Structures en aciers
inoxydables
Ta slovenski standard je istoveten z: EN 1993-1-4:2025/prA1
ICS:
77.140.20 Visokokakovostna jekla Stainless steels
91.010.30 Tehnični vidiki Technical aspects
91.080.13 Jeklene konstrukcije Steel structures
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
EN 1993-1-4:2025
NORME EUROPÉENNE
EUROPÄISCHE NORM
prA1
May 2026
ICS 91.010.30; 91.080.13
English Version
Eurocode 3 - Design of steel structures - Part 1-4: Stainless
steel structures
Eurocode 3 - Calcul des structures en acier - Partie 1-4 : Eurocode 3 - Bemessung und Konstruktion von
Structures en aciers inoxydables Stahlbauten - Teil 1-4: Tragwerke aus nichtrostenden
Stählen
This draft amendment is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 250.

This draft amendment A1, if approved, will modify the European Standard EN 1993-1-4:2025. If this draft becomes an
amendment, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for
inclusion of this amendment into the relevant national standard without any alteration.

This draft amendment 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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1993-1-4:2025/prA1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Modifications throughout the whole document . 4
2 Modifications to the Introduction . 4
3 Modifications to Clause 3, “Terms, definitions and symbols” . 5
4 Modifications to Clause 5, “Materials” . 5
5 Modifications to Clause 7, “Structural analysis” . 5
6 Modifications to Clause 8, “Ultimate limit states” . 6
7 Modifications to Clause 10, “Connection design” . 6

8 Modification to Annex A, “Selection of materials and durability” . 6
European foreword
This document (EN 1993-1-4:2025/prA1:2026) 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 amend EN 1993-1-4:2025.
NOTE Some modifications are purely editorial corrections to improve the quality of the document and these will
not be tagged in the consolidated publication, as noted after the modification.
The following main changes to EN 1993-1-4:2025 are included in the amendment:
— clarification of the definition of λ in consideration of second order effects (7.2.1) and replacement
of λ with λ in the calculation of the amplitude of the imperfection in elastic critical buckling
0 0m
modes (7.3.2);
— addition of a NDP for the value of η for use in determining the shear buckling resistance;
— permission to use preload levels up to 0,7 fA ;
ub s
— requirements for how to classify a new stainless steel grade in a corrosion resistance class according
to Table A.3.
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.
1 Modifications throughout the whole document
Add “-1:2023+A1:2026” to the reference “EN 1990” in Clause 2 and update throughout the text when a
dated reference is given.
Add part number “-1” to the reference “EN 1990” and update throughout the text when an undated reference
is given.
Remove “Fpr” from “FprEN 1993-1-14:2025” throughout the whole document and from “FprEN 1993-1-4”
in the title of 1.1.
2 Modifications to the Introduction
In 0.1, replace “— New parts are under development, e.g. Eurocode for design of structural glass”
with “— EN 19100 Eurocode 10 — Design of glass structures”.
In 0.1, add the following new list item: “— New parts are under development, e.g. Eurocode for design of
fibre-polymer composite structures and for design of tensioned membrane structure
...