SIST EN 16681:2016
(Main)Steel static storage systems - Adjustable pallet racking systems - Principles for seismic design
Steel static storage systems - Adjustable pallet racking systems - Principles for seismic design
This European Standard specifies the structural design requirements applicable to all types of adjustable pallet racking systems fabricated from steel members, intended for storage of unit loads and subject to seismic actions.
This European Standard gives also guidelines for the design of clad rack buildings in seismic zones, where requirements are not covered in the EN 1998 series.
This European Standard does not cover other generic types of storage structures. Specifically, this European Standard does not apply to mobile storage systems, drive-in, drive-through and cantilever racks or static steel shelving systems.
This European Standard does not apply to the design of seismic isolated racking structures.
Ortsfeste Regalsysteme aus Stahl - Verstellbare Palettenregale - Leitsätze für die erdbebensichere Gestaltung
Diese Europäische Norm legt die Konstruktionsanforderungen für alle Typen von verstellbaren Palettenregalsystemen aus Stahlbauteilen fest, die für die Lagerung von Ladeeinheiten vorgesehen und Erdbebeneinwirkungen ausgesetzt sind.
Diese Europäische Norm enthält Leitlinien für die Konstruktion von Hochregal-Silos in Erdbebengebieten, soweit die Anforderungen nicht in der EN 1998 erfasst sind.
Diese Europäische Norm gilt nicht für andere Arten von Lagereinrichtungen. Diese Europäische Norm gilt insbesondere nicht für verfahrbare Systeme, Einfahr-, Durchfahr- und Kragarmregale oder ortsfeste Fachbodenregalsysteme aus Stahl.
Diese Europäische Norm gilt nicht für die Gestaltung seismisch isolierter Regalkonstruktionen.
Systèmes de stockage statique en acier - Systèmes de rayonnages à tablettes ajustables - Principes pour le calcul parasismique
La présente Norme européenne spécifie les exigences de calcul des structures, applicables à tous les types de systèmes de rayonnages à palettes réglables fabriqués à partir d’éléments en acier, destinés au stockage d'unités de charge et soumis à des actions sismiques.
La présente Norme européenne donne les lignes directrices pour le calcul des bâtiments de stockage en tôle plaquée situés en zones sismiques dont les exigences ne sont pas couvertes par la série EN 1998.
La présente Norme européenne ne couvre pas les autres types génériques de structures de rayonnage. En particulier, elle ne s'applique pas aux systèmes de stockage mobiles, aux systèmes de rayonnages à accumulation statique et en porte-à-faux, ni aux systèmes de rayonnages à tablettes statiques en acier.
La présente Norme européenne ne s'applique pas au calcul des structures de rayonnages parasismiques.
Stabilni jekleni sistemi za skladiščenje - Sistemi za nastavljive regale za palete - Načela potresno varnega projektiranja
Ta evropski standard določa zahteve za projektiranje konstrukcij, ki se uporabljajo za vse vrste sistemov za nastavljive regale za palete, izdelane iz jeklenih elementov, ki so namenjeni za skladiščenje tovornih enot in izpostavljeni potresnim vplivom.
Ta evropski standard podaja smernice, ki se uporabljajo za projektiranje objektov s platiranimi regali v potresnih območjih in v primerih, ko zahteve niso zajete v standardu EN 1998.
Ta evropski standard ne zajema drugih splošnih vrst skladiščnih struktur. Ta evropski standard se natančneje ne uporablja za premične sisteme za skladiščenje, vstopne, prehodne in konzolne regale ali stabilne jeklene sisteme polic.
Ta evropski standard se ne uporablja za projektiranje struktur z regali, izoliranih pred potresnimi vplivi.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2016
6WDELOQLMHNOHQLVLVWHPL]DVNODGLãþHQMH6LVWHPL]DQDVWDYOMLYHUHJDOH]DSDOHWH
1DþHODSRWUHVQRYDUQHJDSURMHNWLUDQMD
Steel static storage systems - Adjustable pallet racking systems - Principles for seismic
design
Ortsfeste Regalsysteme aus Stahl - Verstellbare Palettenregale - Leitsätze für die
erdbebensichere Gestaltung
Systèmes de stockage statique en acier - Systèmes de rayonnages à tablettes
ajustables - Principes pour le calcul parasismique
Ta slovenski standard je istoveten z: EN 16681:2016
ICS:
53.080 6NODGLãþQDRSUHPD Storage equipment
91.120.25 =DãþLWDSUHGSRWUHVLLQ Seismic and vibration
YLEUDFLMDPL protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 16681
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2016
EUROPÄISCHE NORM
ICS 53.080
English Version
Steel static storage systems - Adjustable pallet racking
systems - Principles for seismic design
Systèmes de stockage statique en acier - Systèmes de Ortsfeste Regalsysteme aus Stahl - Verstellbare
rayonnages à tablettes ajustables - Principes pour le Palettenregale - Leitsätze für die erdbebensichere
calcul parasismique Gestaltung
This European Standard was approved by CEN on 7 April 2016.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16681:2016 E
worldwide for CEN national Members.
Contents Page
European foreword . 5
0 Introduction . 5
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Symbols and abbreviations . 10
4.1 Symbols . 10
4.2 Abbreviations . 12
5 Performance requirements and compliance criteria . 13
5.1 Applicability . 13
5.2 Performance requirements . 13
5.2.1 No collapse requirement . 13
5.2.2 Damage limitation requirement . 13
5.2.3 Movement of unit loads . 13
6 Ground conditions and seismic action . 14
6.1 General . 14
6.2 Damping . 14
.................................................................................................................................... 14
6.3 Importance factor γI
6.4 Horizontal component of the seismic action . 15
6.5 Vertical component of the seismic action . 15
6.6 Design ground displacement . 15
6.7 Racks supported by suspended floors . 16
7 Methods of analysis . 16
7.1 General . 16
7.2 Limitation of the vertical load referred to the critical Euler Load . 16
7.3 Inter-storey drift sensitivity coefficient . 16
7.4 Analysis procedures . 17
7.4.1 General . 17
7.4.2 Second order effects . 17
7.4.3 Lateral Force Method of Analysis (LFMA) . 18
7.4.4 Modal Response Spectrum Analysis (MRSA) . 20
7.4.5 Large Displacement Method of Analysis (LDMA) . 20
7.4.6 Combination of the effects of the components of the seismic action . 20
7.4.7 Displacements calculation . 21
7.5 Design parameters for seismic analysis . 21
7.5.1 General . 21
7.5.2 Design spectrum modification factors . 21
7.5.3 Unit load-beam friction coefficients . 22
7.5.4 Design seismic weight of the unit load . 23
7.5.5 Unit load weight modification factor . 23
7.5.6 Other seismic weights . 24
7.5.7 Weight of the seismic masses . 24
7.5.8 Position of the centre of gravity of the unit load . 24
7.5.9 Positioning tolerances . 26
7.5.10 Structural regularity criteria . 26
7.6 Modelling assumptions for structural analysis . 27
7.6.1 Sub-modelling . 27
7.6.2 Distribution of the masses . 27
7.6.3 Specific modelling requirements for the analysis . 28
7.6.4 Moment redistribution near the upright's base due to the floor reaction . 29
8 Specific rules . 31
8.1 Design concepts . 31
8.1.1 General . 31
8.1.2 Materials . 31
8.1.3 Structural systems . 32
8.1.4 Regularity criteria . 32
8.1.5 Unbraced racks . 38
8.1.6 Rules for the design of low dissipative structures . 39
8.1.7 Rules for the design of dissipative structures . 39
8.1.8 Anchoring conditions . 39
8.2 Structural systems withstanding the seismic action . 40
8.3 Structural types and behaviour factor . 41
8.3.1 Upright frames . 41
8.3.2 Moment resisting frames . 42
8.3.3 Racks with vertical bracings in down aisle direction . 44
9 Seismic analysis and design . 47
9.1 Actions . 47
9.1.1 Actions to be considered simultaneously with earthquake . 47
9.1.2 Actions not to be considered simultaneously with earthquake . 47
9.2 Safety Verifications . 48
9.2.1 Ultimate limit states . 48
9.2.2 Movements of the unit loads . 49
9.3 Pallet beam design . 50
9.3.1 Actions on pallet beams . 50
9.3.2 Buckling length in the horizontal plane . 51
9.3.3 Correction coefficient for horizontal bending . 52
9.3.4 Buckling length factor in the vertical plane . 52
9.3.5 Beam design check . 52
Annex A (informative) Analysis methods including second order effects . 54
Annex B (normative) Evaluation of the unit load — beam friction coefficient . 61
Annex C (informative) Principles for modelling the unit load masses . 66
Annex D (informative) Simplified method to evaluate the influence of the centre of gravity of
the pallet regarding the beam level . 69
Annex E (informative) Principles for the design of racks supported by floors . 70
Annex F (normative) Additional detailing rules for dissipative elements (Concept B) . 72
Annex G (normative) Testing procedure for beam-upright and floor connections for
dissipative design (concept B) . 73
Annex H (informative) Assessment of the stability of the unit load . 76
Annex I (informative) Data to be exchanged between the Specifier/End User and the Rack’s
Supplier . 78
Annex J (normative) Complementary rules to EN 15635 . 79
Annex K (informative) Complementary rules to EN 15629 — Warehouse environmental
condition category . 80
Annex L (informative) A–deviations . 81
Bibliography . 83
European foreword
This document (EN 16681:2016) has been prepared by Technical Committee CEN/TC 344 “Steel static
storage systems”, the secretariat of which is held by UNI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2016 and conflicting national standards
shall be withdrawn at the latest by December 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
0 Introduction
0.1 Effects of seismic actions on racking systems
Racking systems are load bearing structures for the storage and retrieval of goods in warehouses. The
goods are generally stored on pallets or in box containers.
Racking systems are constructed from steel components; although components are standardized, they
are only standard to each manufacturer. These components differ from traditional steel components in
the following regard:
a) continuous perforated uprights;
b) hook-in connections;
c) structural components for racking, which generally consist of cold formed thin gauge members.
In respect of the loads, the self-weight of a rack structure is typically very small or negligible with
respect to the total mass, whereas in a typical building the percentage of dead and permanent loads will
be much greater.
The nature and the distribution of the goods stored on racking systems strongly affect the response and
the safety of the structure under seismic actions. In fact:
— unit loads are in general simply supported vertically by the racking structure and kept in their
position when loaded by inertial actions only by friction;
— unit loads are in general sub-structures with distinct dynamic characteristics in terms of frequency
and damping, and their behaviour affect the response of the system.
During real earthquakes or earthquake simulated on shaking tables, movements of pallets on pallet
beams were observed; these were either very small ones, contributing to the dissipation of energy by
means of friction, or very large, with movements of the pallets that produced their falling between
beams or outside the rack in the aisle. For this reason, friction between pallet and pallet beam and
internal damping in the unit load has a relevant influence in the dynamic response of the rack and
affects the entity of the inertial actions.
Also, the safety of the installation related to the movement and eventual falling of the pallets requires a
proper assessment.
This European Standard deals with all the relevant and specific seismic design issues for racking
systems, based on the criteria of EN 1998-1:2004, Eurocode 8.
0.2 Requirements for EN Standards for racking and shelving in addition to Eurocodes
While the basic technical description of an earthquake is the same for all structures, the general
principles and technical requirements applicable for conventional steel structures have to be adapted
for racking systems, in order to take into account the peculiarities of racking to achieve the requested
safety level.
Also, the methods of analysis and the design requirements need to be addressed to the peculiarity of
racking structures.
The scope of CEN/TC 344 is to establish European Standards providing guidance for the specification,
design methods, accuracy of build and guidance for the user on the safe use of steel static storage
systems.
This, together with the need of harmonized design rules was the reason that European Racking
Federation ERF/FEM Racking and Shelving has taken the initiative for CEN/TC 344. CEN/TC 344 is in
the course of preparation of a number of European Standards for specific types of racking and shelving
and particular applications, which exist in the European Standards (EN) and working group activities
(WG).
0.3 Liaison
CEN/TC 344 “Steel Static Storage Systems” liaise with CEN/TC 250 “Structural Eurocodes”, CEN/TC 135
“Execution of steel structures and aluminium structures” and CEN/TC 149 “Power operated warehouse
equipment”.
0.4 Additional information specific to EN 16681
This European Standard is intended to be used with EN 1998-1, EN 15512 and related standards.
EN 1998-1 is the first of 6 parts; it gives design rules intended to be used for structures fabricated with
conventional materials, including steel.
EN 15512 is the reference standard for the design of racking structures and components; it addresses
the principles of the EN 1990, Eurocode, and EN 1993 series, Eurocode 3, to the adjustable pallet
racking systems and it needs to be applied also when actions are produced by an earthquake.
1 Scope
This European Standard specifies the structural design requirements applicable to all types of
adjustable pallet racking systems fabricated from steel members, intended for storage of unit loads and
subject to seismic actions.
This European Standard gives also guidelines for the design of clad rack buildings in seismic zones,
where requirements are not covered in the EN 1998 series.
This European Standard does not cover other generic types of storage structures. Specifically, this
European Standard does not apply to mobile storage systems, drive-in, drive-through and cantilever
racks or static steel shelving systems.
This European Standard does not apply to the design of seismic isolated racking structures.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
1)
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 (all parts), Eurocode - Basis of structural design
EN 1993 (all parts), Eurocode 3 - Design of steel structures
2)
EN 1998-1:2004 , Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules,
seismic actions and rules for buildings
EN 15512:2009, Steel static storage systems - Adjustable pallet racking systems - Principles for structural
design
EN 15620, Steel static storage systems - Adjustable pallet racking - Tolerances, deformations and
clearances
EN 15629:2008, Steel static storage systems - Specification of storage equipment
EN 15635:2008, Steel static storage systems - Application and maintenance of storage equipment
EN 15878:2010, Steel static storage systems - Terms and definitions
ETAG 001 series, Guideline for European technical approval of metal anchors for use in concrete
1) Complementary rules to existing Norms specific for seismic applications are included in the following annexes:
— Annex I “Data to be exchanged between the Specifier/End User and the rack’s Supplier” as complement to
EN 15629:2008
— Annex J “Complementary rules to EN 15635” as complement to EN 15635:2008
— Annex K “Complementary rules to EN 15629” as complement to EN 15629:2008
2) This document is impacted by the amendment EN 1998-1:2004/A1:2013.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 15878:2010 and
EN 1998-1:2004 and the following apply.
3.1
associated mass
portion of the total mass of the structure affecting the seismic behaviour of the structural element or of
the substructure analysed
3.2
mass regularity
in elevation: situation in which the mass of the individual load level remains constant or reduces
gradually without abrupt changes from the base to the top of the rack
in plan: situation in which the mass is distributed without significant horizontal eccentricity with
respect to the lateral resisting system
3.3
principal directions
down aisle direction and cross aisle direction in a rack
[SOURCE: EN 15878:2010, definitions 3.2.14 and 3.2.15, modified — the content of the defined term
stems from these two original definitions]
3.4
PRSES
person responsible for storage equipment safety
[SOURCE: EN 15635:2008, 3.18]
3.5
rack filling grade reduction factor
R
F
statistical reduction factor intended to take into account the probability that not all of the pallets will be
present and at their maximum weight at the time of the design earthquake
3.6
seismic weight
value of weight of a mass allowed in seismic design for the calculation of the seismic action
3.7
specifier
person or company that provides the supplier with a specification based on user’s requirements
[SOURCE: EN 15629:2008, 3.23]
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, a number of the following symbols may be used together with
standard subscripts, which are given later. Additional symbols and subscripts are defined where they
first occur.
A design value of the seismic action for the reference return period
E,d
a design ground acceleration on type A ground
g
a reference ground acceleration (PGA) for the reference return period of 475 years
gR
b distance between the uprights axes
β lower bound factor for the design spectrum
C ; C correction factors for unit load-beam friction coefficient (lower and upper bound values)
μL μH
d design inter-storey drift above storey i
r,i
ξ viscous damping ratio expressed as percentage of critical damping
ei height of the centre of gravity of the unit load at level i
E Young modulus of the material
E value of the effect due to the design action
d
E design spectrum modification factor
D1
E pallet weight modification factor
D2
E design spectrum modification factor
D3
E effect due to the application of the seismic action along the horizontal axis x
Edx
E effect due to the application of the seismic action along the horizontal axis y
Edy
E effect due to the application of the seismic action along the vertical axis z
Edz
θ inter-storey drift sensitivity coefficient
θi inter-storey drift sensitivity coefficient between levels i and i+1
θ rotation capacity of the beam-end connector
p
F bearing strength of bolted connection
b,Rd
f characteristic strength of the material
k
F horizontal force at level i of the rack
E,i
F bolt’s shear strength
v,Rd
Φ rotation at Mk, both positive and negative
k
G permanent load
i
G characteristic value of the permanent action
k,i
g gravity acceleration
γ importance factor
I
γ material’s factor
M
γ load factor
f
η damping correction factor
H height of the frame bracing pitch or the distance from floor to first horizontal
H/b height to minimum width ratio of an unit load
h inter-storey height above the storey i
i
H horizontal action on the unit load at level i
i
I moment of inertia of the upright
k coefficient related to number of tests
S
K buckling length factor
K effective spectrum modification factor
D
L beam’s length
λ seismic shear force calculation coefficient in LFMA
adimensional slenderness (EN 15512 and EN 1993-1)
λ
M characteristic bending strength obtained from monotonic tests, both positive and negative
k
μ mean value of the unit load-beam friction coefficient obtained from tests
m
μ individual test result of the unit load-beam friction coefficient
n,i
N axial strength of a member
Rd
ΔN additional vertical force at the base of the uprights
base
ΔN additional vertical action at beam-upright intersection
i
μ unit load-beam friction coefficient
S
P constant downward load in the bending test
c
P Euler critical load
cr,E
P total gravity load in the seismic design situation
E
P total gravity load at and above the considered storey i, in the seismic design situation
E,i
P total product weight on the rack
E,prod
q behaviour factor
q displacement behaviour factor
d
q behavior factor of the rack
rack
Q characteristic value of a variable action
k,i
Q specified weight of the unit load (see EN 15629, 6.7.1)
P;max
Q specified value of the weight of unit loads for the compartment, upright frame or global
P;rated
down aisle design (see EN 15512) as specified by the Specifier (see also EN 15629:2008,
6.7.1).
Q specified weight of the product stored at the level i in the seismic condition
p,rated,i
R design resistance of the element
d
R rack filling grade reduction factor
F
s standard deviation of a number of tests results
S soil parameter
S seismic coefficient specified in EN 1998-1:2004, 4.3.5.2 for the analysis of non structural
a
components
S (T) ordinate of the design spectrum (normalized by g)
d
S (T) ordinate of the modified design spectrum for racks (normalized by g)
d,mod
S (T) ordinate of the elastic spectrum (normalized by g)
e
T period of vibration
T fundamental period of vibration
T , T limits of the constant spectral acceleration branch
B C
T period value defining the beginning of the spectrum constant displacement range
D
V seismic base shear force
E
V total seismic storey shear at the considered storey i
E,i
W weight of the seismic mass considered in the analysis
E
W weight of permanent loads
E,G
W weight of the variable loads
E,Q
W total weight of the seismic mass of the rack
E,tot
W seismic design weight of the unit load to be considered in the seismic analysis
E,UL
ψ combination factor for variable actions
2,i
Z distance from the ground level to the fixing level of the rack
4.2 Abbreviations
LFMA Lateral Force Method of Analysis
MRSA Modal Response Spectrum Analysis
LDMA Large Displacement Method of Analysis
5 Performance requirements and compliance criteria
5.1 Applicability
Non-seismic design shall comply with EN 15512. The reference to the tests and quality control of
components and materials is based on EN 15512.
In case of very low seismicity conditions, the racking structures need not to be designed for earthquake
(see also EN 1998-1:2004, 3.2.1, (5)P).
National Regulations shall be followed to define general conditions of applicability of the seismic design.
It is recommended to consider as very low seismicity cases either those in which the design ground
acceleration on type A ground, γ a , is not greater than 0,04 g, or those where the product γ a S is not
I gR I gR
greater than 0,05 g.
5.2 Performance requirements
5.2.1 No collapse requirement
The racking structure shall be designed and constructed to withstand the design seismic action without
local or general collapse, retaining its structural integrity and a residual load bearing capacity after the
seismic event.
Ultimate limit states are those associated with the collapse, or with other forms of structural failure,
that may endanger the safety of people.
The structural system shall be verified as having the specified resistance and ductility.
5.2.2 Damage limitation requirement
No specific design requirement is prescribed in this European Standard. The movement of the stored
unit loads does not constitute damage.
NOTE Reference is made to Annex J (normative) for integrity controls after a seismic event.
5.2.3 Movement of unit loads
Movement of unit loads shall be considered in the design when appropriate.
NOTE 1 Seismic accelerations can cause sliding of the pallets on the supporting beams, when the inertial
horizontal forces on the pallet exceed the static friction force between pallet and beam.
This effect has been demonstrated by full scale tests to occur for small values of ground accelerations
(low intensity earthquakes) with wooden or plastic pallets on painted or zinc coated steel beams,
because of the structural amplification of the seismic forces at the highest storage levels.
The consequences of these phenomena are the reduction of the seismic action on the rack, due to the
energy dissipation and the limitation of the horizontal action that can be transferred from the pallet to
the rack structure, and the risk of unit loads falling, that can cause local or global collapse of the rack,
or injury to people.
NOTE 2 The modification of the seismic response of the structure is considered in this European Standard by
means of three coefficients that estimate the effects of typical phenomena of racking structures, such
as energy dissipation due to the pallet-beam friction, damping due to the movement of the stored
products, pallet flexibility, and others:
— E and E is the design spectrum modification factors,
D1 D3
— E is the mass modification factor.
D2
The PRSES shall assess the risks related to the sliding of the unit loads and the possibility of their falling
from the rack.
The guidelines for this evaluation are given in 9.2.2.
6 Ground conditions and seismic action
6.1 General
The earthquake motion at a given point of the Earth's surface is defined in EN 1998-1 and related
National Annexes.
When the soil properties are not known in sufficient detail to determine the site soil conditions, Ground
type D is assumed.
6.2 Damping
When not otherwise specified, the viscous damping ratio ξ of the unloaded rack's steel structure,
expressed as percentage of the critical damping, shall be assumed equal to:
ξ = 3 %
NOTE The damping ratio of the loaded racking structure in operating conditions is higher and is taken into
account in E (see 7.5.2).
D3
6.3 Importance factor γ
I
Importance factors not less than the ones defined in Table 1 shall be used. The Specifier is responsible
for the selection of the Importance Class and the design life for the rack.
NOTE 1 The minimum 30 year design life is solely in relation to the seismic design and differs from the normal
static design life of minimum 10 years as given in EN 15512.
Higher importance factors can be specified. Unless otherwise required, the importance factor for the
rack need not to be greater than the importance factor specified for the part of the building in which the
racks are located.
Table 1 — Importance factors for racks
Importance factor γ
I
Importance
Description
30 years 50 years
Class
design life design life
Warehouses with fully automated storage
I 0,67 0,8
operations
Standard warehouse conditions, including
II 0,84 1,0
picking areas
Any kind of rack with random public access for
III N/A 1,2
private customer
Hazardous product storage
(Hazardous products storage is subject to the
IV N/A 1,4
approval of National Authorities)
Strategic facilities
The default value of conventional warehouse racks shall be 30 years for Class I and II, and 50 years for
clad rack buildings.
If National regulations require different design life this shall be considered.
NOTE 2 Importance class I: 20 % probability of exceedance of the seismic action in 30 years and 50 years.
Importance class II: 10 % probability of exceedance of the seismic action in 30 years and 50 years.
Importance class III: 5,8 % probability of exceedance of the seismic action in 50 years.
Importance class IV: 3,65 % probability of exceedance of the seismic action in 50 years.
6.4 Horizontal component of the seismic action
The horizontal component of the seismic action shall be evaluated according to EN 1998-1.
6.5 Vertical component of the seismic action
The vertical component of the seismic action shall be evaluated according to EN 1998-1.
The vertical component of the seismic action need only to be taken into account in the following
relevant cases as shown in Figure 1:
a) cantilever components;
b) beams supporting columns (for example in order picking tunnels);
c) elements or substructures supporting cantilevers or supported by beams.
Key
1 cantilever components
2 beams supporting columns (for example in order picking tunnels)
3 their directly associated supporting elements or substructures
Figure 1 — Elements to be designed for vertical component of the seismic action
6.6 Design ground displacement
The design ground displacement shall be evaluated according to EN 1998-1.
6.7 Racks supported by suspended floors
The design of racks supported by suspended floors shall be based on realistic model including the
structure on which the rack is installed.
Alternatively, response spectra including the effect of the dynamic response of the supporting structure
and its interaction with the supported rack can be used; guidance is given in Annex E (informative).
7 Methods of analysis
7.1 General
The reference method for the evaluation of the seismic effects on the racking structures is the modal
response spectrum analysis. This shall be performed using a linear elastic model of the structure and
the modified design spectrum S (T) defined in 7.5.1, and, when applicable, the design spectrum for
d,mod
the vertical component defined in 6.5.
7.2 Limitation of the vertical load referred to the critical Euler Load
In all cases when γ a S ≥ 0,1g (or other value prescribed in the National Annex to EN 1998-1 or
I gR
National Regulations) the following limitation shall be fulfilled:
PP ≤ 0,5
E cr ,E
where
PE is the total gravity load of the rack in the seismic design situation;
P is the Euler critical load.
cr,E
P shall be obtained either from buckling analysis or approximated according to Annex B, C and G of
cr,E
EN 15512:2009.
7.3 Inter-storey drift sensitivity coefficient
The requirement to account for second order effects is related to the maximum value of the inter-storey
drift sensitivity coefficient defined as:
θ = Pd V h (1)
( ) ( )
i E ,,i ri E ,i i
θθ= max
[ ]
i
where
θ is inter-storey drift sensitivity coefficient for the fundamental mode at storey i;
i
P is total gravity load above the considered storey, in the seismic design situation;
E,i
d is design inter-storey drift, evaluated as the difference of the average lateral
r,i
displacements at the top and bottom of the storey under consideration and calculated
according to 7.4.7 by means of linear elastic 1st order analysis;
V is total seismic storey shear at the considered storey i;
E,i
h is inter-storey height above the considered storey i;
i
θ is Inter-storey drift sensitivity coefficient for the fundamental mode.
Alternatively, the inter-storey drift sensitivity coefficient θ is obtainable as follows:
θ q× PP (2)
d E cr ,E
where
P is total gravity load of the rack in the seismic design situation;
E
P is Euler critical load;
cr,E
q is displacements behaviour factor.
d
NOTE 1 The total gravity load in seismic conditions P is determined from the specified value of unit loads
E
and the rack filling factor R defined in 7.5.4.
Qp,rated F
NOTE 2 Refer to the EN 1998 series for the definition of q
d.
7.4 Analysis procedures
7.4.1 General
The procedures described below shall be applied (see Tables 2 and 3).
Other methods of analysis can be used according to EN 1998-1.
7.4.2 Second order effects
7.4.2.1 General
When θ ≤ 0,1, second order effects can be neglected.
Second order effects shall be considered according to 7.4.2.2 for low dissipative concept and 7.4.2.3 for
dissipative concept.
7.4.2.2 Low dissipative concept (behaviour factor q ≤ 2)
Analysis methods directly considering second order effects shall be used (see Annex A); the applicable
methods of analysis are summarized in Table 2.
Alternatively they can be approximated by multiplying seismic action effects obtained from first order
analysis by a factor equal to 1/(1-θ).
Amplification of 2nd order effects by factor 1/(1-θ) is in general conservative; it is not recommended if
θ > 0,3 as results tend to be unduly conservative.
7.4.2.3 Dissipative concept (behaviour factor q > 2)
The applicable methods of analysis for dissipative design concept are summarized in Table 3.
If θ ≤ θ analysis methods directly considering second order effects should be used (see Annex A).
Alternatively they could be approximated by multiplying the seismic action effects obtained from first
order analysis by a factor equal to 1/(1-θ).
If θ ≤ θ , pushover analysis according to EN 1998-1 or large displacement analysis presented in 7.4.5
(Large Displacement Method of Analysis - LDMA) shall be used.
If θ > θ , a time history analysis including large displacements and nonlinear behaviour of materials and
connections shall be used.
Time-history analysis shall be according to EN 1998-1.
The following values may be assumed:
=
θ = 0,3
θ = 0,5
Table 2 — Summary of methods of analysis for low dissipative structural behaviour
Method of
θ Second order effects
analysis
θ ≤ 0,1 Negligible
LFMA
Shall be either
(7.4.3)
considered directly in the
or
analysis
θ > 0,1
MRSA
or
(7.4.4)
approximated
NOTE For racks not regular in plan and elevation, refer
to EN 1998–1.
Table 3 — Summary of methods of analysis for dissipative structural behaviour
Method of
θ Second order effects
analysis
LFMA
θ ≤ 0,1 Negligible
(7.4.3)
Shall be either
or
θ ≤ θ considered directly in the
MRSA
analysis or approximated
(7.4.4)
Pushover analysis according
θ ≤ θ to EN 1998–1
or LDMA according to 7.4.5
Time history analysis including
θ > θ
2 geometrical and material nonlinearity
according to EN 1998–1
NOTE For racks not regular in plan and elevation, refer to
EN 1998–1.
7.4.3 Lateral Force Method of Analysis (LFMA)
This method of analysis can be applied when response is not significantly affected by contribution of
higher modes of vibration in each principal direction.
This requirement is considered fulfilled either for structures:
— that are stiffness and mass regular in elevation with funda
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