FprEN 1993-4-2

SLOVENSKI STANDARD
oSIST prEN 1993-4-2:2024
01-junij-2024
Evrokod 3 - Projektiranje jeklenih konstrukcij - 4-2. del: Rezervoarji
Eurocode 3 - Design of steel structures - Part 4-2: Tanks
Eurocode 3 - Bemessung und Konstruktion von Stahlbauten - Teil 4-2: Tankbauwerke
Eurocode 3 - Calcul des structures en acier - Partie 4-2 : Réservoirs
Ta slovenski standard je istoveten z: prEN 1993-4-2
ICS:
23.020.10 Nepremične posode in Stationary containers and
rezervoarji tanks
91.010.30 Tehnični vidiki Technical aspects
91.080.13 Jeklene konstrukcije Steel structures
oSIST prEN 1993-4-2:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1993-4-2:2024
oSIST prEN 1993-4-2:2024
DRAFT
EUROPEAN STANDARD
prEN 1993-4-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2024
ICS 91.010.30; 91.080.13; 23.020.10 Will supersede EN 1993-4-2:2007
English Version
Eurocode 3 - Design of steel structures - Part 4-2: Tanks
Eurocode 3 - Calcul des structures en acier - Partie 4-2 : Eurocode 3 - Bemessung und Konstruktion von
Réservoirs Stahlbauten - Teil 4-2: Tankbauwerke
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 1993-4-2:2024 E
worldwide for CEN national Members.

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Contents Page
European foreword . 5
0 Introduction . 6
1 Scope . 9
1.1 Scope of EN 1993-4-2 . 9
1.2 Assumptions . 10
2 Normative references . 10
3 Terms, definitions, symbols, sign conventions and units . 11
3.1 Terms and definitions . 11
3.2 Symbols . 16
3.2.1 Roman upper-case letters . 16
3.2.2 Roman lower-case letters . 17
3.2.3 Greek letters . 19
3.2.4 Subscripts . 19
3.3 Sign conventions . 20
3.3.1 Conventions for global tank structure axis system . 20
3.3.2 Conventions for structural element axes in circular tanks . 22
3.3.3 Conventions for stress resultants for circular tanks . 22
4 Basis of design . 24
4.1 Basic requirements . 24
4.2 Units . 25
4.3 Tank classification . 25
4.3.1 Reliability differentiation . 25
4.3.2 Structural complexity classification for tanks . 25
4.3.3 Tank group classification . 27
4.4 Verification by the partial factor method . 27
4.4.1 Partial factors for actions on tanks . 27
4.4.2 Partial factors for resistances . 28
4.4.3 Serviceability limit states . 28
4.5 Limit states . 29
4.6 Actions and environmental effects . 29
4.7 Material properties . 29
4.8 Geometrical data . 29
4.9 Modelling of the tank for determining action effects . 29
4.10 Design assisted by testing . 29
4.11 Durability . 29
5 Properties of materials . 30
5.1 General. 30
5.2 Structural carbon and carbon manganese steels . 31
5.3 Structural stainless steels . 31
5.4 Toughness requirements . 32
5.4.1 General. 32
5.4.2 Minimum design metal temperature . 32
6 Basis for structural analysis . 33
6.1 Ultimate limit states . 33
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6.1.1 Basis . 33
6.1.2 Plate thickness to be used in resistance calculations . 33
6.1.3 Fatigue . 33
6.1.4 Allowance for temperature effects . 33
6.2 Analysis of the circular cylindrical shell structure of a tank . 33
6.2.1 Modelling of the structural shell . 33
6.2.2 Methods of analysis . 33
6.2.3 Geometric imperfections and tolerances . 36
6.3 Tanks constructed using corrugated sheeting . 36
7 Design of cylindrical shell walls . 37
7.1 Basis . 37
7.1.1 General . 37
7.1.2 Cylindrical shell wall design . 37
7.1.3 Catch basins . 38
7.2 Resistance of the cylindrical shell. 38
7.2.1 General . 38
7.3 Cylindrical shell plate thickness in a stepped-wall to resist liquid pressures . 39
7.4 Design for resistance to external pressure and wind . 42
7.4.1 General . 42
7.4.2 The primary ring to provide top boundary for buckling under external pressure and
wind . 43
7.4.3 Stepped shell wall design for buckling under external pressure and wind . 43
7.4.4 Secondary rings to increase the buckling resistance under external pressure and
wind . 48
7.5 Differential settlement . 50
7.5.1 General . 50
7.5.2 Local differential settlement in tanks with floating roofs . 51
7.6 Support arrangements for a cylindrical shell . 51
8 Design of circular roof structures . 51
8.1 General . 51
8.2 Alternative roof structural forms . 52
8.3 Considerations for individual structural forms . 53
8.3.1 Unsupported shell roof structure . 53
8.4 Conical, spherical dome or flat roof with rafter or truss supporting structure . 53
8.4.1 Plate design general . 53
8.4.2 Conical roof plate design using nonlinear theory . 54
8.4.3 Design of the roof supporting structure . 55
8.4.4 Flat or inverted cone roof design . 55
8.4.5 Dome roof design . 56
8.4.6 Roof centre ring . 58
8.4.7 Column supported roof structure . 59
8.4.8 Bracing and rings where roof plates are not connected to the rafters . 59
8.5 Spherical or conical shell roof without roof supporting structure . 60
9 Roof to shell junction and primary ring (eaves junction) . 61
9.1 General: conventional arrangement . 61
9.2 Primary ring or girder at the shell to roof junction (eaves ring) . 61
9.3 Inverted cone roof primary ring or girder at the shell to roof junction . 64
10 Tank bottoms and annular plates . 65
10.1 General . 65
10.2 Annular plates . 66
10.3 Bottom central plates (sketch plates) . 67
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11 Openings in the cylindrical shell or roof . 68
11.1 General. 68
11.2 Shell nozzles of small size . 68
11.3 Design of cylindrical shell manholes, access doors and nozzles of large size for LS1 69
11.4 Cylindrical shell wall design for LS3 in the presence of shell openings . 70
11.5 Design of openings in the roof . 71
12 Design for static stability of anchored and unanchored tanks . 71
12.1 Unanchored ground supported tanks . 71
12.1.1 Uplift . 71
12.1.2 Overturning. 72
12.2 Anchorage design for anchored ground supported tanks . 72
12.2.1 General. 72
12.2.2 Anchorage design . 73
13 Ultimate limit states in pedestal tanks . 74
13.1 Structural forms . 74
13.2 Actions on pedestal tanks . 75
13.3 Design of conical segments . 75
13.4 Design of spherical and toroidal segments . 75
13.5 Tower design . 75
14 Serviceability limit states . 75
14.1 Cylindrical shell wall . 75
14.2 Tank roofs . 76
Bibliography . 77

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European foreword
This document (prEN 1993-4-2:2024), 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 supersede EN 1993-4-2:2007 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 the EN 1993 series
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 in itself 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;
EN 1993-1-3, Design of Steel Structures — Part 1-3: Cold-formed members and sheeting;
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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 from the
structural type such as structural fire design, cold-formed members and sheeting, stainless steels, plated
structural elements, 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 EN 1993-4-2
EN 1993-4-2 gives design requirements for the structural design of tanks for the storage of liquid and
liquified gas products. It gives design rules that supplement the generic rules in the many parts of
EN 1993-1. This document 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.
0.5 National Annex for EN 1993-4-2
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 EN 1993-4-2 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.
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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 EN 1993-4-2 through notes to the following clauses:
4.3.2(3) 4.3.3(2) 4.4.1(3) 4.4.2(4)
4.4.3(2) 4.11(4) 7.1.3(1) 8.4.7(1)
10.2(1) 10.2(9) 10.3(2)
National choice is allowed in EN 1993-4-2 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 1993-4-2
(1) EN 1993-4-2 provides rules for structural design of vertical cylindrical, conical and pedestal
above-ground steel tanks for the storage of liquid and liquified gas products.
(2) EN 1993-4-2 is applicable to the design for resistance of cylindrical walls and flat bottoms
constructed using unstiffened plates. The design of conical and dome roofs as shell structures
(unsupported) or as supported on a structural framework (supported) are also covered.
(3) EN 1993-4-2 is only applicable to the requirements for resistance and structural stability of steel
tanks.
(4) EN 1993-4-2 only covers steel tank structures in Tank Groups 1, 2 and 3, as defined in this
document.
NOTE Tank Group 4 is not defined in this standard (see 3.1.41).
(5) This document is applicable to tanks within the following dimensional limits (see EN 1991-4):
Tank aspect ratio h /d < 10
S
Tank total height h < 70 m
S
Tank diameter d < 100 m
(6) This standard includes suitable rules for the design of tanks intended to store solids suspended
in a liquid, where the appropriate global density of the mixture is used.
NOTE Tanks used for the separation of mineral particles of different density fall into this category.
(7) EN 1993-4-2 does not apply to the following:
a) tanks with gross capacity less than 5 m (5 000 l);
b) dished-end tanks that have a diameter less than 5 m;
c) tanks with characteristic internal pressures above the liquid surface greater than 50 kPa (500 mbar)
(see pressure equipment directive);
d) design metal temperatures outside the ranges defined in Clause 5, with −50 °C being the lowest
temperature for the application of this document;
e) tanks of rectangular and other non-circular planforms;
f) tanks exposed to fire;
g) floating roofs and floating covers;
h) ancillary structures such as stairways, platforms, nozzles, piping and access doors.
(8) This document does not cover
a) the special requirements for seismic design of tanks,

All pressures are in bar gauge unless otherwise specified.
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b) the design of a supporting structure,
c) the design of ancillary structures such as stairways, platforms, pipe racks and ladders,
d) the design of an aluminium roof structure on a steel tank,
e) reinforced concrete foundations for steel tanks,
f) the design of a conical hopper,
g) the design of a transition junction between the base of a cylindrical shell wall and a conical hopper,
h) the design of a supporting ring girder in an elevated tank.
1.2 Assumptions
(1) Unless specifically stated, EN 1990, the EN 1991 series and the EN 1993-1 series apply.
(2) The design methods given in this document apply 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 the EN 1993
series, or in the relevant material and product specifications.
(3) This standard applies to axisymmetric structures, but includes the effects of unsymmetrical
actions (e.g. wind), and unsymmetrically supported tanks (e.g. on discrete supports).
(4) EN 1993-4-2 is intended to be used in conjunction with EN 1990, with EN 1991-4, with the other
Parts of EN 1991, with EN 1993-1-6 and EN 1993-4-1, with the other Parts of EN 1993, with EN 1992 and
with the other Parts of EN 1994 to EN 1999 relevant to the design of tanks. Matters that are already
covered in those documents are not repeated.
(5) Numerical values for partial factors and other reliability parameters are recommended as basic
values that provide an acceptable level of reliability. They have been selected assuming that an
appropriate level of workmanship and quality management applies.
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
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

As impacted by EN 1990:2023/prA1:2024
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3 Terms, definitions, symbols, sign conventions and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions from EN 1990, ISO 8930 and the following
apply.
3.1.1
axial direction
x
vertical direction on the shell wall
Note 1 to entry: For a cylindrical wall, the axial and meridional directions are identical.
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 or annular plate
structural member that passes around the circumference of the structure beneath the cylindrical shell
wall and is required to ensure that the assumed boundary conditions are achieved in practice
3.1.4
catch basin
external tank structure to contain liquid that could escape by leakage or accident from the primary tank
Note 1 to entry: This type of structure is usually used where the primary tank contains toxic or hazardous liquids.
A catch basin also effectively reduces the requirement for an extensive area of liquid containment around the tank.
3.1.5
circumferential direction
θ
horizontal tangent to the shell wall at any point
Note 1 to entry: It varies around the tank, lies in the horizontal plane and is tangential to the shell wall.
3.1.6
continuously supported tank
tank 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
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 (see 3.1.39)
Note 1 to entry: The cylindrical shell wall of the tank is formed by making horizontal joints between a series of
short cylindrical sections, termed strakes, each formed by making vertical joints between individual curved plates.
3.1.8
curb angle
light ring attached to the top of the cylindrical shell wall of a tank
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3.1.9
discrete support
situation in which a tank is supported using a local bracket or column, giving a limited number of narrow
supports around the tank circumference
3.1.10
eaves junction
joint between a cylindrical wall and a roof structure
Note 1 to entry: See also curb angle and primary ring.
3.1.11
externally stiffened wall
tank wall with stiffeners attached to the outside of the tank wall
3.1.12
fixed shell roof
roof structure that is attached to the top of the cylindrical wall
Note 1 to entry: This term includes both roofs supported on rafters or a structural frame and an unstiffened shell
roof (sometimes referred to as unsupported).
3.1.13
floating roof
roof structure that floats on the surface of the stored liquid, sliding up and down within the tank as the
liquid level varies
3.1.14
gas/vapour pressure
pressure in the space above the surface of the stored liquid
3.1.15
ground supported tank
tank where the shell structure is uniformly supported on a horizontal foundation supported directly by
the ground
3.1.16
hopper
converging section towards the bottom of a tank
Note 1 to entry: It is used to channel liquids towards a gravity discharge outlet (usually when they contain
suspended solids).
3.1.17
horizontally corrugated wall
shell wall constructed from corrugated steel sheets where the troughs pass around the circumference of
the tank
3.1.18
internally stiffened wall
tank wall with stiffeners attached to the inside of the tank wall
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3.1.19
isotropic wall
shell wall of a tank constructed from flat rolled steel sheet
3.1.20
joint efficiency factor
ratio of the membrane resistance of a welded or bolted joint to the yield membrane resistance of the
parent plate
3.1.21
junction
point at which any two or more shell segments are connected
Note 1 to entry: It can include a stiffener or can have no stiffener: the point of attachment of a ring stiffener to the
shell is treated as a junction.
3.1.22
maximum design liquid level
MDLL
highest liquid level in a tank which is used as an accidental load design situation
Note 1 to entry: This is higher than the maximum normal operating level (see Figure 3.1).
3.1.23
maximum normal operating liquid level
MNOL
highest liquid level in a tank under normal operating conditions and used in load combinations according
to EN 1990:2023, Clause A.4
Note 1 to entry: This is lower than the maximum design liquid level (see Figure 3.1)
3.1.24
meridional direction
ϕ
tangent to the shell wall at any point in a plane that passes through the axis of the tank
Note 1 to entry: It varies according to the structural element being considered. For a cylindrical wall, the axial and
meridional directions are identical, and axial is generally the preferred term.
3.1.25
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
3.2.26
minimum operating liquid level
min NOL
lowest liquid level in a tank under normal operations
Note 1 to entry: See Figure 3.1.
3.1.27
purlin
circumferentially oriented structural member supporting a roof and supported itself on rafters
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3.1.28
primary ring
ring located near the top of the cylindrical wall or at the eaves junction
Note 1 to entry: It can also be referred to as the top ring or wind girder. Where there is a roof, the primary ring also
serves the purpose of forming the junction between the roof and cylindrical wall.
3.1.29
rafter
radially oriented structural member supporting a roof structure
3.1.30
rib
local member that provides a primary load-carrying path for loads causing bending down the meridian
of a shell, representing a generator of the shell of revolution
Note 1 to entry: It is used to distribute transverse loads on the structure by bending action.
3.1.31
ring girder or ring beam
circumferential stiffener which has bending stiffness and strength normal to the plane of the circular
section of a shell as well as in that plane
Note 1 to entry: It is a primary load-carrying element, used to distribute local vertical loads into the shell.
3.1.32
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 to have no 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.
3.1.33
RLG
refrigerated liquefied gas
3.1.34
secondary ring stiffener
ring stiffener on a tank wall located on the cylindrical wall below the primary ring
Note 1 to entry: There can be multiple secondary rings. The purpose of the secondary ring is to increase the
buckling resistance of the cylindrical shell under external pressure and wind.
3.1.35
separation of ring stiffeners
centre to centre distance between the circumferential axes of two adjacent ring stiffeners
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3.1.36
shell
vertical wall of a ground-supported cylindrical tank
Note 1 to entry: The term shell is often used in the tank industry to refer to the vertical wall of a ground-supported
cylindrical tank. This usage is slightly confusing when compared with the general definition of a shell (see
EN 1993-1-6) which has more general application. To avoid confusion, the term “shell” is used in this standard
where appropriate to the needs of the tank industry, but the term “cylindrical wall” is more generally used.
3.1.37
shell-roof junction
junction between a cylindrical shell wall and the roof
Note 1 to entry: Alternatively known as the top angle or eaves junction, is the junction between the vertical wall
and the roof.
3.1.38
sketch plate or bottom plate
plating used to form the internal bottom of a ground-supported tank
3.1.39
strake
single row of plates of a given thickness
Note 1 to entry: The cylindrical shell wall of a tank is formed by making horizontal circumferential joints between
a group of short cylindrical sections, each termed a strake, formed by making vertical joints between individual
curved plates. Several strakes normally form one course (see 3.1.7).
3.1.40
tank
vessel for storing liquid products
Note 1 to entry: In this standard it is assumed to be circular in plan.
3.1.41
Tank Group
TG
classification of a tank to identify the sophistication of its design requirements, according to its size, form
and usage, placing it into Tank Group 0, 1, 2 or 3
Note 1 to entry: Tanks in Consequence Class 4 are in Tank Group 4. For these tanks additional considerations are
necessary.
Note 2 to entry: The provisions of this standard are not required for TG0. All the provisions are intended to apply
to TGs 1, 2 and 3, except where exemptions are specifically made for TG1 or TG2.
3.1.42
shell wall
metal plate elements forming the vertical walls, roof or a hopper bottom of a tank
Note 1 to entry: This term is not restricted to the vertical walls.
oSIST prEN 1993-4-2:2024
prEN 1993-4-2:2024 (E)
3.1.43
Structural Complexity Class
SCC
classification of a tank to address the complexity of the structural form, insofar as is necessary to meet
the susceptibility to different failure modes
3.1.44
test pressure
pressure in the space above the test liquid during the test procedure
3.1.45
transition junction
junction between the vertical shell wall and a conical hopper
Note 1 to entry: The junction can be at the base of the vertical wall or part way down it.
3.1.46
unsupported shell roof structure
shell roof that has no truss or rafter structural framework beneath it, but relies on the resistance of the
shell alone to carry loads and transfer them to the cylindrical wall of the tank
3.1.47
vertical stiffener
stiffener attached to the cylindrical shell wall in the axial direction
Note 1 to entry: It is sometimes used on elevated tanks to enhance the axial buckling resistance.
3.1.48
wind girder
substantial primary ring near the top of the cylindrical shell to provide both stiffness against buckling
and strength against induced stresses under wind loading
3.2 Symbols
For the purposes of this document, the following symbols apply.
The symbols used are based on ISO 3898.
3.2.1 Roman upper-case letters
A area of structural member cross-section;
A , A area of top, bottom flange of roof centre ring;
1 2
E Young’s modulus of elasticity;
E reduced elastic modulus to account for thermal effects;
red
F force;
F maximum vertical downward design distributed load on a roof including the weight of the plating,
A
supporting structure and external vertical loads;
F maximum vertical downward design distributed load on a roof including the weight of the plating,
B
supporting structure and external vertical loads;
I second moment of area of cross-section;
K reduction factor for the effect of axial compression on buckling under external pressure;
a
oSIST prEN 1993-4-2:2024
prEN 1993-4-2:2024 (E)
M bending moment in a structural member;
N axial force in a structural member;
N minimum number of load cycles relevant for fatigue;
f
P vertical load on a roof rafter;
r
R linear elastic buckling resistance (see EN 1993-1-6)
cr
T temperature;
T reference temperature for design;
Ed
T lowest one-day mean ambient temperature (see 5.4.2);
LODMAT
TMDMT minimum design metal temperature (see 5.4.2);
W elastic section modulus.
3.2.2 Roman lower-case letters
a is the horizontal side
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