FprEN 1993-4-1

SLOVENSKI STANDARD
oSIST prEN 1993-4-1:2024
01-junij-2024
Nadomešča:
SIST EN 1993-4-1:2007
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: prEN 1993-4-1
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
oSIST prEN 1993-4-1:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1993-4-1:2024
oSIST prEN 1993-4-1:2024
DRAFT
EUROPEAN STANDARD
prEN 1993-4-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2024
ICS 65.040.20; 91.010.30; 91.080.13 Will supersede EN 1993-4-1:2007
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 European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 250.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

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

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, 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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1993-4-1:2024 E
worldwide for CEN national Members.

oSIST prEN 1993-4-1:2024
prEN 1993-4-1:2024 (E)
Contents Page
European foreword . 5
0 Introduction . 6
1 Scope . 9
1.1 Scope of EN 1993-4-1 . 9
1.2 Assumptions . 10
2 Normative references . 11
3 Terms, definitions, symbols, sign conventions and units . 11
3.1 Terms and definitions . 11
3.2 Symbols used in Part 4.1 of Eurocode 3 . 15
3.3 Sign conventions . 20
4 Basis of design . 28
4.1 Basic requirements . 28
4.2 Units . 28
4.3 Silo classifications . 29
4.4 Verification by the partial factor method . 32
4.5 Actions and environmental effects . 33
4.6 Geometrical data . 33
4.7 Modelling of the silo for determining action effects . 34
4.8 Design assisted by testing . 34
4.9 Action effects for limit state verifications . 34
4.10 Durability . 34
4.11 Fire resistance . 34
5 Properties of materials . 34
5.1 General. 34
5.2 Structural steels . 35
5.3 Stainless steels . 35
5.4 Special alloy steels . 35
5.5 Toughness requirements . 35
6 Basis for structural analysis . 36
6.1 Ultimate limit states . 36
6.2 Serviceability limit states . 37
6.3 Analysis of the structure of a shell silo . 37
6.4 Analysis of the box structure of a plate assembly silo . 40
6.5 Analysis treatment of corrugated sheeting . 41
7 Ultimate limit state design of cylindrical shell walls . 44
7.1 Basis . 44
7.2 Distinctions between cylindrical shell forms . 45
7.3 Resistance of isotropic welded or bolted cylindrical walls . 46
7.4 Resistance of isotropic cylindrical walls under axial compression . 48
7.5 Resistance of isotropic cylindrical walls under external pressure, internal partial vacuum
and wind . 55
7.6 Interactions between axial compression, circumferential compression and membrane
shear in isotropic walls . 62
7.7 Isotropic walls under cyclic loads . 62
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7.8 Resistance of isotropic walls with vertical stiffeners . 62
7.9 Resistance of horizontally corrugated cylindrical walls . 66
7.10 Vertically corrugated cylindrical walls with ring stiffeners . 75
7.11 Detailing for openings in cylindrical walls . 76
8 Support conditions for cylindrical walls . 78
8.1 Shell with its base fully supported . 78
8.2 Isotropic shell supported by a skirt . 78
8.3 Isotropic cylindrical shell wall with engaged columns . 78
8.4 Framework support beneath an isotropic walled silo . 79
8.5 Discretely supported isotropic cylindrical shell without a ring girder . 81
8.6 Discretely supported isotropic cylindrical shell with a ring girder . 82
8.7 Discretely supported isotropic cylindrical shell with an intermediate ring . 83
8.8 Discretely supported isotropic silo with columns beneath the hopper . 87
8.9 Local support details and ribs for load introduction in isotropic cylindrical walls . 87
8.10 Anchorage at the base of an isotropic walled silo . 89
8.11 Isotropic walled cylindrical shells with vertical stiffeners with the base fully supported 90
8.12 Corrugated stiffened cylindrical shells with the base fully supported . 90
9 Ultimate limit state design of isotropic conical hoppers. 91
9.1 Basis. 91
9.2 Isotropic hopper wall design . 91
9.3 Resistance of isotropic conical hoppers . 92
9.4 Considerations for special hopper structures . 99
10 Ultimate limit state design of transition junctions and supporting ring girders in circular
silos . 100
10.1 Basis. 100
10.2 Analysis of the transition junction . 103
10.3 Structural resistances for isotropic junctions . 112
10.4 Limit state verifications for isotropic transition junctions . 117
10.5 Considerations concerning support arrangements for the junction . 120
11 Ultimate limit state design of circular conical roof structures . 120
11.1 Basis. 120
11.2 Distinctions between roof structural forms . 120
11.3 Resistance of circular conical isotropic silo roofs . 121
12 Ultimate limit state design of rectangular and planar-sided silos. 122
12.1 Basis. 122
12.2 Classification of planar sided structural forms . 122
12.3 Resistance of unstiffened vertical walls . 123
12.4 Resistance of silo walls composed of stiffened or corrugated plates . 124
12.5 Silos with internal ties . 127
12.6 Strength of pyramidal hoppers . 133
12.7 Vertical stiffeners on box walls . 133
12.8 Support requirements for plate assemblies . 133
13 Serviceability requirements . 134
13.1 General . 134
13.2 Cylindrical isotropic and isotropic stiffened shell walls . 134
13.3 Cylindrical corrugated and corrugated stiffened walls . 135
13.4 Conical hoppers . 135
13.5 Rectangular and planar-sided silos . 135
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Annex A (informative) Simplified rules for isotropic walled circular silos in Silo Group 1 . 137
A.1 Use of this Annex . 137
A.2 Scope and field of application . 137
A.3 Action combinations for Silo Group 1 . 137
A.4 Action effect assessment . 137
A.5 Ultimate limit state assessment. 137
Annex B (informative) Simplified rules for transition junction ring girders in circular silos with
horizontally corrugated wall and vertical stiffeners . 144
B.1 Use of this Annex . 144
B.2 Scope and field of application . 144
B.3 Evaluation of the circumferential force in the transition ring . 144
B.4 Evaluation of the circumferential force in the transition ring . 145
B.5 Determination of the buckling resistance of the transition ring . 147
Annex C (informative) Expressions for membrane stress resultants in conical hoppers . 149
C.1 Use of this Annex . 149
C.2 Scope and field of application . 149
C.3 General hopper theory pressures (as per EN 1991-4) . 149
C.4 Uniform normal pressure p with wall friction µp . 150
o o
C.5 Linearly varying normal pressure from p at apex to p at transition with wall friction µp
1 2
.......................................................................................................................................................................... 150
C.6 “Radial stress field” normal pressure pattern with triangular switch stress below the
transition . 150
Bibliography . 152

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European foreword
This document (prEN 1993-4-1:2024), has been prepared by Technical Committee CEN/TC250
“Structural Eurocodes”, the Secretariat of which is held by BSI. CEN/TC 250 is responsible for all
Structural Eurocodes and has been assigned responsibility for structural and geotechnical design
matters by CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN1993-4-1:2007 and its amendments and corrigenda.
The first generation of EN Eurocodes was published between 2002 and 2007. This document forms
part of the second generation of the Eurocodes, which have been prepared under Mandate M/515
issued to CEN by the European Commission and the European Free Trade Association.
The Eurocodes have been drafted to be used in conjunction with relevant execution, material,
product and test standards, and to identify requirements for execution, materials, products and
testing that are relied upon by the Eurocodes.
The Eurocodes recognize the responsibility of each Member State and have safeguarded their right
to determine values related to regulatory safety matters at national level through the use of National
Annexes.
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0 Introduction
0.1 Introduction to the Eurocodes
The Structural Eurocodes comprise the following standards generally consisting of a number of Parts:
— EN 1990, Eurocode — Basis of structural and geotechnical design
— EN 1991, Eurocode 1 — Actions on structures
— EN 1992, Eurocode 2 — Design of concrete structures
— EN 1993, Eurocode 3 — Design of steel structures
— EN 1994, Eurocode 4 — Design of composite steel and concrete structures
— EN 1995, Eurocode 5 — Design of timber structures
— EN 1996, Eurocode 6 — Design of masonry structures
— EN 1997, Eurocode 7 — Geotechnical design
— EN 1998, Eurocode 8 — Design of structures for earthquake resistance
— EN 1999, Eurocode 9 — Design of aluminium structures
— New parts are under development, e.g. Eurocode for design of structural glass.
0.2 Introduction to EN 1993 (all parts)
EN 1993 applies to the design of buildings and civil engineering works in steel. It complies with the
principles and requirements for the safety and serviceability of structures, the basis of their design and
verification that are given in EN 1990 – Basis of structural and geotechnical design.
EN 1993 is concerned only with requirements for resistance, serviceability, durability and fire resistance
of steel structures. Other requirements, e.g. concerning thermal or sound insulation, are not covered.
EN 1993 is subdivided in various parts:
EN 1993-1, Design of Steel Structures — Part 1: General rules and rules for buildings;
EN 1993-2, Design of Steel Structures — Part 2: Bridges;
EN 1993-3, Design of Steel Structures — Part 3: Towers, masts and chimneys;
EN 1993-4, Design of Steel Structures — Part 4: Silos and tanks;
EN 1993-5, Design of Steel Structures — Part 5: Piling;
EN 1993-6, Design of Steel Structures — Part 6: Crane supporting structures;
EN 1993-7, Design of steel structures — Part 7: Sandwich panels.
EN 1993-1 does not exist as a physical document, but comprises the following 14 separate parts, the basic
part being EN 1993-1-1:
EN 1993-1-1, Design of Steel Structures — Part 1-1: General rules and rules for buildings;
EN 1993-1-2, Design of Steel Structures — Part 1-2: Structural fire design;
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EN 1993-1-3, Design of Steel Structures — Part 1-3: Cold-formed members and sheeting;
NOTE Cold formed hollow sections supplied according to EN 10219 are covered in EN 1993-1-1.
EN 1993-1-4, Design of Steel Structures — Part 1-4: Stainless steel structures;
EN 1993-1-5, Design of Steel Structures — Part 1-5: Plated structural elements;
EN 1993-1-6, Design of Steel Structures — Part 1-6: Strength and stability of shell structures;
EN 1993-1-7, Design of Steel Structures — Part 1-7: Plate assemblies with elements under transverse loads;
EN 1993-1-8, Design of Steel Structures — Part 1-8: Joints;
EN 1993-1-9, Design of Steel Structures — Part 1-9: Fatigue;
EN 1993-1-10, Design of Steel Structures — Part 1-10: Material toughness and through-thickness
properties;
EN 1993-1-11, Design of Steel Structures — Part 1-11: Tension components;
EN 1993-1-12, Design of Steel Structures — Part 1-12: Additional rules for steel grades up to S960;
EN 1993-1-13, Design of Steel Structures — Part 1-13: Beams with large web openings;
EN 1993-1-14, Design of Steel Structures — Part 1-14: Design assisted by finite element analysis.
All subsequent parts EN 1993-1-2 to EN 1993-1-14 treat general topics that are independent of the
structural type such as structural fire design, cold-formed members and sheeting, stainless steels, plated
structural elements, shell structures, etc.
All subsequent parts numbered EN 1993-2 to EN 1993-7 treat topics relevant for a specific structural
type such as steel bridges, towers, masts and chimneys, silos and tanks, piling, crane supporting
structures, etc. EN 1993-2 to EN 1993-7 refer to the generic rules in EN 1993-1 and supplement, modify
or supersede them.
0.3 Introduction to prEN 1993-4-1
prEN 1993-4-1 gives design guidance for the structural design of silos and design rules that supplement
the generic rules in the parts of EN 1993-1.
prEN 1993-4-1 is intended for clients, designers, contractors and relevant authorities.
0.4 Verbal forms used in the Eurocodes
The verb “shall" expresses a requirement strictly to be followed and from which no deviation is permitted
in order to comply with the Eurocodes.
The verb “should” expresses a highly recommended choice or course of action. Subject to national
regulation and/or any relevant contractual provisions, alternative approaches could be used/adopted
where technically justified.
The verb “may" expresses a course of action permissible within the limits of the Eurocodes.
The verb “can" expresses possibility and capability; it is used for statements of fact and clarification of
concepts.
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0.5 National Annex for prEN 1993-4-1
National choice is allowed in this standard where explicitly stated within notes. National choice includes
the selection of values for Nationally Determined Parameters (NDPs).
The national standard implementing prEN 1993-4-1 can have a National Annex containing all national
choices to be used for the design of buildings and civil engineering works to be constructed in the relevant
country.
When no national choice is given, the default choice given in this standard is to be used.
When no national choice is made and no default is given in this standard, the choice can be specified by a
relevant authority or, where not specified, agreed for a specific project by appropriate parties.
National choice is allowed in prEN 1993-4-1 through notes to the following clauses:
4.3.2(4) 4.3.3(1) 4.3.3(3) 4.3.3(8)
4.4.1.2(3) 4.4.2(2) 4.5.3(1) 5.4(1)
6.1.4(6) 7.5.4(3) 12.5.2(9)
National choice is allowed in prEN 1993-4-1 on the application of the following informative annexes:
None
The National Annex can contain, directly or by reference, non-contradictory complementary information
for ease of implementation, provided it does not alter any provisions of the Eurocodes.

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1 Scope
1.1 Scope of 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 h /d < 10
b c
— Silo total height h < 70 m
b
— Silo equivalent diameter d < 60 m
c
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.
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(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.

a) Circular planform silo b) Rectangular planform silo
Key
1 transition 7 conical hopper
2 column: supporting structure 8 EN 1993-1-1 applies below this line
3 skirt 9 pyramidal roof
4 conical roof 10 rectangular box
5 cylindrical shell or barrel 11 ring girder
6 ring 12 pyramidal hopper
Figure 1.1 — Terminology used in silo structures
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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.
EN 1090-2, Execution of steel structures and aluminium structures — Part 2: Technical requirements for
steel structures
1 1
EN 1990:2023 , Eurocode — Basis of structural and geotechnical design
EN 1991 (all parts), Eurocode 1— Actions on structures
EN 1993 (all parts), Eurocode 3 — Design of steel structures
ISO 8930, General principles on reliability for structures — Vocabulary
3 Terms, definitions, symbols, sign conventions and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1990, ISO 8930 and the following
apply.
3.1.1
axial direction
vertical tangent to a cylindrical silo wall
Note 1 to entry: For the cylinder alone, it coincides with the meridional direction.
3.1.2
axisymmetric shell
shell structure whose geometry is defined by rotation of a meridional line about a central axis
3.1.3
base ring
structural member that passes around the circumference of the structure at the base and provides means
of attachment of the structure to a foundation or other element
Note 1 to entry: It is required that the assumed boundary conditions are achieved in practice.
3.1.4
box
structure formed from an assembly of flat plates into a three-dimensional enclosed form
Note 1 to entry: For the purposes of this Standard, the box has dimensions that are generally comparable in all
directions.
3.1.5
circumferential direction
horizontal tangent to the silo wall at any point
Note 1 to entry: The circumferential direction varies around the silo, lies in the horizontal plane and is tangential
to the silo wall irrespective of whether the silo is circular or rectangular in plan.

As impacted by EN 1990:2023/prA1:2024.
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3.1.6
continuously supported silo
silo in which all positions around the circumference are supported in an identical manner
Note 1 to entry: Minor departures from this condition (e.g. a small opening) need not affect the applicability of the
definition.
3.1.7
corrugated silo wall
shell strake of a circular silo that is formed from sheet that has been rolled before construction into a
corrugated form (rounded or trapezoidal undulations) that provides enhanced bending resistance in one
direction
Note 1 to entry: See 6.5. This term also refers to a wall in a rectangular or polygonal silo where trapezoidal
undulations are used to enhance the bending resistance.
3.1.8
course
section of the height of a cylindrical wall constructed from a single plate thickness or between ring
stiffeners, usually made up of several strakes
Note 1 to entry: See 3.1.32.
3.1.9
cylindrical shell
vertical walled section of a circular planform silo
Note 1 to entry: See Figure 1.1.
3.1.10
discrete support
position in which a silo is supported using a local bracket or column, giving a limited number of narrow
supports around the silo circumference
Note 1 to entry: Four or six discrete supports are commonly used, but three or more than six are also found.
3.1.11
hopper
converging section towards the bottom of a silo, normally conical in form
Note 1 to entry: It is used to channel solids towards a gravity discharge outlet.
3.1.12
isotropic conical hopper
conical hopper that is formed from rolled flat sheets
Note 1 to entry: These sheets can be welded or bolted together.
3.1.13
isotropic shell
shell segment of a silo that is formed from rolled flat sheets
Note 1 to entry: These sheets can be welded or bolted together.
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3.1.14
isotropic shell with vertical stiffeners
isotropic shell segment with attached vertical stiffeners that can be rolled or cold-formed sections and
can be external or internal to the shell
3.1.15
joint efficiency factor
ratio of the membrane resistance of a welded or bolted joint to the yield membrane resistance of the
parent plate
3.1.16
junction
point at which any two or more shell segments, or two or more flat plate elements of a box, meet
Note 1 to entry: The junction can include a ring stiffener or can be unstiffened.
Note 2 to entry: The point of attachment of a ring stiffener to the shell or box can be treated as a junction.
3.1.17
meridional direction
tangent at any point to the silo wall in a vertical plane
Note 1 to entry: The meridional direction varies according to the structural element being considered (cylindrical,
conical or spherical). Alternatively, it is the vertical or inclined direction on the surface of the structure that a
raindrop would take in sliding down the surface.
3.1.18
middle surface
middle of the shell wall at any point, such that under elastic conditions, this surface is stress free when
the shell is subject only to bending in any direction
Note 1 to entry: This term can also refer to the middle plane of a flat plate that forms part of a box.
3.1.19
pyramidal hopper
converging section towards the bottom of a silo, inverted pyramidal in form
Note 1 to entry: In EN 1993-4-1, it is assumed that the geometry is simple, consisting of only four planar elements
of trapezoidal shape.
3.1.20
rib
local member that provides a primary load-carrying path for loads causing bending down the meridian
of a shell or flat plate, representing a generator of the shell of revolution or a vertical stiffener on a box
Note 1 to entry: A rib is used to distribute transverse loads on a shell structure by bending action.
3.1.21
ring girder or ring beam
circumferential stiffener which has bending stiffness and strength both normal to the plane of the circular
section of a shell or the plan section of a rectangular structure and also in that plane
Note 1 to entry: This ring beam is a primary load-carrying element, used to distribute local vertical support forces
into the shell or box structure.
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3.1.22
ring stiffener
local stiffening member that passes around the circumference of the structure at a given point on the
meridian
Note 1 to entry: It is assumed that the ring stiffener has no effective stiffness in the meridional plane of the
structure. It is provided to increase the stability or to introduce local loads, not as a primary load-carrying element.
In a shell of revolution, it is circular, but in rectangular structures is takes the rectangular form of the plan section.
3.1.23
separation of stiffeners
centre to centre distance between the longitudinal centroidal axes of two adjacent parallel stiffeners
3.1.24
shell
structure formed from a curved, thin plate, made from either a flat or a corrugated plate
Note 1 to entry: The shell can be stiffened with discrete external or internal structural members. Its shape can be
cylindrical, conical or spherical.
3.1.25
shell segment
component part of a shell structure that consists of separate pieces, each of which is formed from a
curved, thin plate
Note 1 to entry: The segment is the full zone that is cylindrical, conical or spherical even when composed of
multiple plates.
3.1.26
silo
vessel for storing particulate granular solids
Note 1 to entry: In this docu,ent, the silo is assumed to have a vertical form with solids being added by gravity at
the top. The term silo includes all forms of structure to store particulate solids and is sometimes referred to as a bin,
hopper, grain tank or bunker.
3.1.27
silo fundamental loading case
SFLC
loading derived from the stored solid that is close to symmetrical under all conditions leading to simpler
situations for structural design
Note 1 to entry: These load cases are defined in EN 1991-4.
3.1.28
silo group
SG
categorization of each silo in terms of complexity of the structural design requirements, based on its size,
form and usage
Note 1 to entry: Each silo is identified as belonging to one of the Silo Groups 0, 1, 2 and 3 according to the
sophistication of the structural design requirements
Note 2 to entry: This standard does not cover silos in Consequence Class 4, so SG4 is not defined. The provisions of
this standard are not required for SG0. The provisions are all intended for SGs 1, 2 and 3, except where exemptions
are specifically made for SG1 or SG2.
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3.1.29
silo special load case
SSLC
loading condition derived from the stored solid that is unsymmetrical to the structure, leading to more
complicated design load cases for structural design
Note 1 to entry: These load cases are defined in prEN 1991-4:2024, 3.1.30.
skirt
part of the cylindrical shell that lies below the transition junction
Note 1 to entry: The skirt differs from the higher part in that it has no contact with the stored bulk solid.
3.1.31
smeared stiffener analysis
analysis of the shell in which stiffeners are treated as integral to the wall leading to the shell wall
properties being a composite section
Note 1 to entry: A width of shell equal to an integer multiple of the separation of the stiffeners is used to define the
smeared shell properties. The stiffness properties of a smeared shell wall are orthotropic with eccentric terms
leading to coupling between bending and stretching behaviour.
3.1.32
strake
single row of plates of a given thickness
Note 1 to entry: The cylindrical shell wall of a silo is formed by making horizontal circumferential joints between a
set of short cylindrical sections, each termed a strake, and formed by making vertical joints between individual
curved plates. Several strakes normally form one course (see 3.1.8)
3.1.33
stringer stiffener
local stiffening member that follows the meridian of a shell, representing a generator of the shell of
revolution
Note 1 to entry: It is provided to increase the stability, or to assist with the introduction of local loads or to carry
axial loads. It is not intended to provide a primary load-carrying capacity for bending due to transverse loads.
3.1.34
Structural Complexity Class
SCC
classification of a silo to address the complexity of the structural form, insofar as a different precision in
the definition of actions is needed to meet the susceptibility to different failure modes
3.1.35
transition junction
junction between the cylindrical wall of a silo and a hopper beneath it
Note 1 to entry: The junction can be at the base of the cylinder or part way down it if the cylinder includes a skirt.
3.2 Symbols used in Part 4.1 of Eurocode 3
The symbols used are based on ISO 3898.
oSIST prEN 1993-4-1:2024
prEN 1993-4-1:2024 (E)
3.2.1 Roman upper-case letters
A area of cross-section;
C membrane stretching stiffness;
C buckling coefficient;
D bending flexural rigidity;
E Young’s modulus of elasticity;
E reduced elastic modulus to account for thermal effects;
red
F force;
G shear modulus;
H height of structure;
I second moment of area of a cross-section;
I second moment of area of a ring cross-section;
r
I second moment of area of cross-section for bending in the axial direction;
x
I second moment of area of cross-section for bending in the circumferential direction;
θ
J uniform torsion constant;
K flexural stiffness of wall panel;
L height of shell segment or length of vertical stiffener;
M bending moment;
N axial force;
P force per unit circumference;
Q fabrication tolerance quality of construction of a shell susceptible to buckling;
V force per unit length on a tie;
W vertical force on a hopper.
NOTE The coordinate x is used in EN 1993-1-6 for the axial direction (also termed meridional) in cylindrical
shells. If x is used as the meridional coordinate in all cases, a problem arises where conical roofs and hoppers are
involved, since x is strictly the axial coordinate in the global system. For cylinders, the meridional and axial
coordinates coincide, but in EN 1993-4-1 it is important to make the key distinction between the axial and
meridional directions, so x is used exclusively for axial. The treatment of hoppers and conical roofs uses the
meridional coordinate φ as shown in Figure 3.1 and Figure 3.3.
3.2.2 Roman lower-case letters
a coefficient;
b width of plate or stiffener;
d silo equivalent diameter (see EN 1991-4);
c
d crest to crest dimension of a corrugation;
cr
d circumferential distance between adjacent axial stiffeners;
s
e eccentricity of force or stiffener;
f yield strength of steel;
y
oSIST prEN 1993-
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