SIST EN 1993-4-1:2026/oprA1:2026

• Abstract:

  1.1 Scope of EN 1993 4 1; (1) prEN 1993 4 1 provides rules for the structural design of steel silos of circular or rectangular plan-form, being free-standing (on ground) or supported on a structural framework (elevated).; (2) prEN 1993 4 1 is applicable to silos constructed from isotropic rolled plates that are stiffened or unstiffened, from corrugated sheeting that is stiffened or unstiffened and from flat or corrugated plates assembled into box structures of different geometries. It applies to vertical walls, hoppers, roof structures, transition junctions and support structures.; (3) prEN 1993 4 1 does not apply to storage vessels for silage and haylage, or to the storage of materials that are not free-flowing (see EN 1991 4). This Part 4-1 also does not cover:; - resistance to fire;; - cylindrical silos with internal subdivisions;; - internal structures within a single silo (except for internal ties, as defined in 12.5);; - silos with capacity less than 100 kN (10 tonnes);; - hoppers that are supported on a structural framework;; - cases where special measures are necessary to limit the consequences of accidents.; (4) This document is applicable to silos within the following dimensional limits (see EN 1991-4):; - Silo aspect ratio hb/dc < 10 ; - Silo total height hb < 70 m ; - Silo equivalent diameter dc < 60 m ; NOTE These dimensional limitations are more limited than those of EN 1991-4 which also applies to silos constructed from other materials.; (5) Where this standard applies to circular planform silos, the geometric form is restricted to axisymmetric structures, but unsymmetrical actions on them and supports that induce forces in the silo structure that are not axisymmetric are included.; (6) This part is concerned only with the requirements for resistance and stability of steel silos. For other requirements (such as operational safety, functional performance, fabrication and erection, quality control, details like man-holes, flanges, filling devices, outlet gates and feeders, etc.), see other relevant standards and information.; (7) This part is concerned with both isolated silo structures and silos that are connected to others to form a battery of silos, but throughout this document the term silo refers to a single cell within a battery.; (8) Provisions relating to special requirements of seismic design are provided in EN 1998 4, which complements or adapts the provisions of Eurocode 3 specifically for this purpose.; (9) The structural design of supporting structures for the silo are dealt with in EN 1993 1 1. The supporting structure is deemed to consist of all structural elements beneath the bottom flange of the lowest ring of the silo (see Figure 1.1), though information on some forms of support structure is given in Clause 8 of this document.; (10) Foundations in reinforced concrete for steel silos are dealt with in EN 1992 (all parts) and EN 1997 (all parts).; 1.2 Assumptions; (1) Unless specifically stated, the provisions of EN 1990, EN 1991 (all parts) and EN 1993 1 (all parts) apply.; (2) The design methods given in EN 1993 4 1 are applicable if:; - the execution quality is as specified in EN 1090 2, and; - the construction materials and products used are as specified in the relevant parts of EN 1993 (all parts), or in the relevant material and product specifications.; Figure 1.1 - Terminology used in silo structures; ...

• Status: Not Published
• Public Enquiry End Date: 26-Nov-2026
• ICS: 65.040.20 - Buildings and installations for processing and storage of agricultural produce
• ICS: 91.010.30 - Technical aspects
• ICS: 91.080.13 - Steel structures
• Technical Committee: KON - Structures
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 25-Sep-2026
• Due Date: 12-Feb-2027
• Ref Project: EN 1993-4-1:2026/prA1 - Eurocode 3 - Design of steel structures - Part 4-1: Silos

• Amends: kSIST FprEN 1993-4-1:2025 - Eurocode 3 - Design of steel structures - Part 4-1: Silos
• Effective Date: 10-Jun-2026

SIST EN 1993-4-1:2026/oprA1:2026 is the Slovenian draft amendment to EN 1993-4-1:2026, Eurocode 3 - Design of steel structures - Part 4-1: Silos. It updates the structural design rules for steel silos, including circular, rectangular and polygonal forms, and refines several design checks, terms, formulas and figures used in practice.

What does SIST EN 1993-4-1:2026/oprA1:2026 specify?

SIST EN 1993-4-1:2026/oprA1:2026 modifies the rules for steel silo design in EN 1993-4-1:2026. The base part covers silos that are free-standing on the ground or supported on a structural framework, and this amendment revises the parts of the document that support that design work.

The underlying scope covers silos made from rolled plates, corrugated sheeting, and flat or corrugated plates assembled into box structures. It applies to vertical walls, hoppers, roof structures, transition junctions and support structures, while excluding silage and haylage vessels, non-free-flowing stored materials, fire resistance, internal subdivisions, most internal structures, very small silos, framework-supported hoppers and accident-limit cases.

Part of the document	What it covers
Introduction	Updates references and wording
Clause 3	Terms, definitions, symbols, sign conventions and units
Clause 4	Basis of design
Clause 7	Ultimate limit state design of cylindrical shell walls
Clause 8	Support conditions for cylindrical walls
Clause 10	Ultimate limit state design of transition junctions and base rings in circular silos
Clause 12	Ultimate limit state design of rectangular and polygonal silos
Annex A	Simplified rules for isotropic walled circular silos in Silo Group 1
Annex C	Formulae for membrane stress resultants in conical hoppers

What are the key requirements of SIST EN 1993-4-1:2026/oprA1:2026?

SIST EN 1993-4-1:2026/oprA1:2026 mainly tightens and clarifies design rules rather than changing the scope of silo design. The most important practical effect is that several checks, especially for ring stiffness, support conditions and classification, are made more explicit.

• Clause 4 / Table 4.1 clarifies how to choose the Structural Complexity Class. It adds or refines the grouping for elevated discretely-supported silos, silos with a Special Load Case, silos with higher values of w, and double-walled or other non-conventional silo structures. In practice, this affects which design route and level of checking are used.
• Clause 7.5.2 revises the method for the top ring of an open silo under external pressure, internal vacuum and wind. It gives a more explicit basis for the required second moment of area and points to LBA analysis or GNA analysis outside the stated slenderness range. For a designer, this means the upper edge stiffness check is more clearly tied to the silo geometry.
• Clause 8.10 updates support-condition rules for cylindrical walls, including the criterion using L/d and the expression for the minimum top-ring stiffness parameter. This matters when deciding whether a wall behaves as continuously supported and how strong the support zone must be.
• Clause 10.2 and 10.3 update the transition junction and base-ring rules by correcting figures and notation. The design logic stays focused on the junction between shell and base, but the geometry references are cleaned up.
• Clause 12.5 revises formulas for rectangular and polygonal silos and changes the term tube to hollow section. This affects the checking of internal ties and related member descriptions.
• Annex A replaces the symbols l and ℓ with L in the simplified rules for isotropic walled circular silos in Silo Group 1. That reduces ambiguity in calculations.
• Annex C clarifies the hopper coordinate system for conical hoppers. This helps users apply the membrane stress resultants correctly.

What terms does SIST EN 1993-4-1:2026/oprA1:2026 define?

SIST EN 1993-4-1:2026/oprA1:2026 uses technical terms that matter directly in silo checks.

• Structural Complexity Class - the classification used in Table 4.1 to sort silos into the right design category.
• Silo Special Load Case - a load-case condition used in Table 4.1 for class selection.
• LBA analysis - the analysis used in Clause 7.5.2 for lower L/r values to confirm buckling resistance of the upper ring.
• GNA analysis - the analysis used in Clause 7.5.2 for higher L/r values to confirm buckling resistance of the upper ring.
• Meridian - the updated term used for the shell direction previously described with the word generator in several clauses.
• Axisymmetric structures - the circular-planform silo form covered by the scope, with unsymmetrical actions still included in the design checks.
• Hollow section - the member type named in Clause 12.5.4 for the relevant rectangular and polygonal silo detail.

Who uses SIST EN 1993-4-1:2026/oprA1:2026?

SIST EN 1993-4-1:2026/oprA1:2026 is used by structural engineers, silo designers, checking engineers, and steel fabricators working on steel silos and their support structures. It is also relevant to quality and procurement staff who need to know which execution and material standards the design rules rely on.

The standard is especially relevant in storage and processing installations, including agricultural produce facilities named by the classification of the document. It helps teams decide how to design the shell, roof, hopper, transition junctions, support structure and related tie members.

What changed in SIST EN 1993-4-1:2026/oprA1:2026 from the previous edition?

SIST EN 1993-4-1:2026/oprA1:2026 modifies EN 1993-4-1:2026. The main changes listed in the amendment are:

• clarifications on choosing the Structural Complexity Class depending on parameter w
• correction of the method for determining the required top ring stiffness for an open silo under external pressure, internal vacuum and wind
• correction of wording and typing errors throughout the document
• revised terminology and symbols in Clause 3
• revised figures and formulas in Clauses 10 and 12
• updates to Annex A and Annex C

Which standards are used with SIST EN 1993-4-1:2026/oprA1:2026?

SIST EN 1993-4-1:2026/oprA1:2026 is used together with several Eurocode parts and execution standards.

Standard	What it contributes
EN 1990-1	Basis of structural and geotechnical design for new structures
EN 1990	General basis of structural design where stated
EN 1991 (all parts)	Actions on structures
EN 1991-4	Silo actions and load cases, including special load cases
EN 1993 (all parts)	Steel design rules and material-related provisions
EN 1993-1-1	Design of supporting structures
EN 1998-4	Special requirements for seismic design
EN 1992 (all parts)	Reinforced concrete foundations
EN 1997 (all parts)	Geotechnical design for foundations
EN 1090-2	Execution quality for the construction assumed by the design methods

What does the SIST EN 1993-4-1:2026/oprA1:2026 document contain?

SIST EN 1993-4-1:2026/oprA1:2026 contains amendment text rather than a full reissue of the base standard. It updates the introduction, terminology, basis of design, shell-wall design, support conditions, transition junctions, rectangular and polygonal silo design, and two annexes.

The document includes revised tables, formulas and figures that support design checks, especially for ring stiffness, support conditions, internal ties and hopper stress resultants. Those elements are used for structural design, verification and checking of steel silos, not for operational or fabrication detailing.

SLOVENSKI STANDARD
01-november-2026
Evrokod 3 - Projektiranje jeklenih konstrukcij - 4-1. del: Silosi
Eurocode 3 - Design of steel structures - Part 4-1: Silos
Eurocode 3 - Bemessung und Konstruktion von Stahlbauten - Teil 4-1: Silos
Eurocode 3 - Calcul des structures en acier - Partie 4-1: Silos
Ta slovenski standard je istoveten z: EN 1993-4-1:2026/prA1
ICS:
65.040.20 Poslopja in naprave za Buildings and installations for
predelavo in skladiščenje processing and storage of
kmetijskih pridelkov agricultural produce
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 1993-4-1:2026
NORME EUROPÉENNE
EUROPÄISCHE NORM
prA1
September 2026
ICS 65.040.20; 91.010.30; 91.080.13
English Version
Eurocode 3 - Design of steel structures - Part 4-1: Silos
Eurocode 3 - Calcul des structures en acier - Partie 4-1: Eurocode 3 - Bemessung und Konstruktion von
Silos Stahlbauten - Teil 4-1: Silos
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 1993-4-1:2026. 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 1993-4-1:2026/prA1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Modifications to the Introduction . 4
2 Modifications to Clause 3, "Terms, definitions, symbols, sign conventions and units" . 4
3 Modifications to Clause 4, “Basis of design” . 4
4 Modifications to Clause 7, “Ultimate limit state design of cylindrical shell walls” . 5
5 Modifications to Clause 8, “Support conditions for cylindrical walls” . 6
6 Modifications to Clause 10, “Ultimate limit state design of transition junctions and base
rings in circular silos” . 6
7 Modifications to Clause 12, “Ultimate limit state design of rectangular and polygonal
silos” . 7
8 Modification to Annex A, “Simplified rules for isotropic walled circular silos in Silo Group
1” . 7
9 Modification to Annex C, “Formulae for membrane stress resultants in conical hoppers” . 7

European foreword
This document (EN 1993-4-1:2026/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 1993-4-1:2026.
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 1993-4-1:2026 are included in the amendment:
— clarifications on the choice of the Structural Complexity Class depending on the parameter w
(Table 4.1),
— correction of the method to determine the necessary top ring stiffness for an open silo to resist
buckling under external pressure, internal vacuum and wind (subclause 7.5.2),
— correction of several wordings and typing errors throughout the document.
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 to the Introduction
In 0.1 replace “— New parts are under development, e.g. EN 19101 Eurocode 11 for design of fibre-
polymer composite structures and EN 19102 Eurocode 12 for
...