EN 1991-1-4:2005

SLOVENSKI STANDARD
01-oktober-2005
1DGRPHãþD
SIST ENV 1991-2-4:1998
Evrokod 1: Vplivi na konstrukcije – 1-4. del: Splošni vplivi – Obtežbe vetra
Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions
Eurocode 1: Einwirkungen auf Tragwerke - Teil 1-4: Allgemeine Einwirkungen -
Windlasten
Eurocode 1 : Actions sur les structures - Partie 1-4 : Actions générales - Actions du vent
Ta slovenski standard je istoveten z: EN 1991-1-4:2005
ICS:
91.010.30 7HKQLþQLYLGLNL Technical aspects
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 1991-1-4

NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2005
ICS 91.010.30 Supersedes ENV 1991-2-4:1995
English version
Eurocode 1: Actions on structures - Part 1-4: General actions -
Wind actions
Eurocode 1: - Actions sur les structures - Partie 1-4: Eurocode 1: Einwirkungen auf Tragwerke - Teil 1-4:
Actions générales - Actions du vent Allgemeine Einwirkungen - Windlasten
This European Standard was approved by CEN on 4 June 2004.

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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1991-1-4:2005: E
worldwide for CEN national Members.

Contents Page
Section 1 General 9
1.1 Scope 9
1.2 Normative references 10
1.3 Assumptions 10
1.4 Distinction between Principles and Application Rules 10
1.5 Design assisted by testing and measurements 10
1.6 Definitions 10
1.7 Symbols 11
Section 2 Design situations 16
Section 3 Modelling of wind actions 17
3.1 Nature 17
3.2 Representations of wind actions 17
3.3 Classification of wind actions 17
3.4 Characteristic values 17
3.5 Models 17
Section 4 Wind velocity and velocity pressure 18
4.1 Basis for calculation 18
4.2 Basic values 18
4.3 Mean wind 19
4.3.1 Variation with height 19
4.3.2 Terrain roughness 19
4.3.3 Terrain orography 21
4.3.4 Large and considerably higher neighbouring structures 21
4.3.5 Closely spaced buildings and obstacles 22
4.4 Wind turbulence 22
4.5 Peak velocity pressure 22
Section 5 Wind actions 24
5.1 General 24
5.2 Wind pressure on surfaces 24
5.3 Wind forces 25
Section 6 Structural factor c c 28
s d
6.1 General 28
6.2 Determination of c c 28
s d
6.3 Detailed procedure 28
6.3.1 Structural factor c c 28
s d
6.3.2 Serviceability assessments 30
6.3.3 Wake buffeting 30
Section 7 Pressure and force coefficients 31
7.1 General 31
7.1.1 Choice of aerodynamic coefficient 31
7.1.2 Asymmetric and counteracting pressures and forces 32
7.1.3 Effects of ice and snow 32
7.2 Pressure coefficients for buildings 33
7.2.1 General 33
7.2.2 Vertical walls of rectangular plan buildings 34
7.2.3 Flat roofs 37
7.2.4 Monopitch roofs 40
7.2.5 Duopitch roofs 43
7.2.6 Hipped roofs 47
7.2.7 Multispan roofs 48
7.2.8 Vaulted roofs and domes 50
7.2.9 Internal pressure 51
7.2.10 Pressure on walls or roofs with more than one skin 53
7.3 Canopy roofs 54
7.4 Free-standing walls, parapets, fences and signboards 61
7.4.1 Free-standing walls and parapets 61
7.4.2 Shelter factors for walls and fences 63
7.4.3 Signboards 63
7.5 Friction coefficients 64
7.6 Structural elements with rectangular sections 65
7.7 Structural elements with sharp edged section 67
7.8 Structural elements with regular polygonal section 67
7.9 Circular cylinders 69
7.9.1 External pressure coefficients 69
7.9.2 Force coefficients 71
7.9.3 Force coefficients for vertical cylinders in a row arrangement 74
7.10 Spheres 74
7.11 Lattice structures and scaffoldings 76
7.12 Flags 78
7.13 Effective slenderness λ and end-effect factor ψ 80
λ
Section 8 Wind actions on bridges 82
8.1 General 82
8.2 Choice of the response calculation procedure 85
8.3 Force coefficients 85
8.3.1 Force coefficients in x-direction (general method) 85
8.3.2 Force in x-direction – Simplified Method 88
8.3.3 Wind forces on bridge decks in z-direction 89
8.3.4 Wind forces on bridge decks in y-direction 90
8.4 Bridge piers 91
8.4.1 Wind directions and design situations 91
8.4.2 Wind effects on piers 91
Annex A (informative) Terrain effects 92
A.1 Illustrations of the upper roughness of each terrain category 92
A.2 Transition between roughness categories 0, I, II, III and IV 93
A.3 Numerical calculation of orography coefficients 95
A.4 Neighbouring structures 100
A.5 Displacement height 101
Annex B (informative)  Procedure 1 for determining the structural factor c c 102
s d
B.1 Wind turbulence 102
B.2 Structural factor 103
B.3 Number of loads for dynamic response 105
B.4 Service displacement and accelerations for serviceability assessments of a
vertical structure 105
Annex C (informative)  Procedure 2 for determining the structural factor c c 108
s d
C.1 Wind turbulence 108
C.2 Structural factor 108
C.3 Number of loads for dynamic response 109
C.4 Service displacement and accelerations for serviceability assessments 109
Annex D (informative)  c c values for different types of structures 111
s d
Annex E (informative) Vortex shedding and aeroelastic instabilities 114
E.1 Vortex shedding 114
E.1.1 General 114
E.1.2 Criteria for vortex shedding 114
E.1.3 Basic parameters for vortex shedding 115
E.1.4 Vortex shedding action 118
E.1.5 Calculation of the cross wind amplitude 118
E.1.6 Measures against vortex induced vibrations 128
E.2 Galloping 129
E.2.1 General 129
E.2.2 Onset wind velocity 129
E.2.3 Classical galloping of coupled cylinders 131
E.3 Interference galloping of two or more free standing cylinders 133
E.4 Divergence and Flutter 134
E.4.1 General 134
E.4.2 Criteria for plate-like structures 134
E.4.3 Divergency velocity 134
Annex F (informative) Dynamic characteristics of structures 136
F.1 General 136
F.2 Fundamental frequency 136
F.3 Fundamental mode shape 141
F.4 Equivalent mass 143
F.5 Logarithmic decrement of damping 143
Bibliography 146
Foreword
This document EN 1991-1-4:2005 has been prepared by Technical Committee CEN/TC250 "Structural
Eurocode", the secretariat of which is held by BSI.
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 October 2005, and conflicting national standards
shall be withdrawn at the latest by March 2010.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard : Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia,
Spain, Sweden, Switzerland and United Kingdom.
This European Standard supersedes ENV 1991-2-4: 1995.
CEN/TC 250 is responsible for all Structural Eurocodes.
Background of the Eurocode programme
In 1975, the Commission of the European Community decided on an action programme in the field of
construction, based on article 95 of the Treaty. The objective of the programme was the elimination of
technical obstacles to trade and the harmonisation of technical specifications.
Within this action programme, the Commission took the initiative to establish a set of harmonised
technical rules for the design of construction works which, in a first stage, would serve as an
alternative to the national rules in force in the Member States and, ultimately, would replace them.
For fifteen years, the Commission, with the help of a Steering Committee with Representatives of
Member States, conducted the development of the Eurocodes programme, which led to the first
generation of European codes in the 1980s.
In 1989, the Commission and the Member States of the EU and EFTA decided, on the basis of an
agreement between the Commission and CEN, to transfer the preparation and the publication of the
Eurocodes to the CEN through a series of Mandates, in order to provide them with a future status of
European Standard (EN). This links de facto the Eurocodes with the provisions of all the Council’s
Directives and/or Commission’s Decisions dealing with European standards (e.g. the Council Directive
89/106/EEC on construction products - CPD - and Council Directives 93/37/EEC, 92/50/EEC and
89/440/EEC on public works and services and equivalent EFTA Directives initiated in pursuit of setting
up the internal market).
The Structural Eurocode programme comprises the following standards generally consisting of a
number of Parts :
EN 1990 Eurocode : Basis of Structural Design
EN 1991 Eurocode 1: Actions on structures
EN 1992 Eurocode 2: Design of concrete structures
EN 1993 Eurocode 3: Design of steel structures

Agreement between the Commission of the European Communities and the European Committee for Standardisation (CEN)
concerning the work on EUROCODES for the design of building and civil engineering works (BC/CEN/03/89).
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
Eurocode standards recognise the responsibility of regulatory authorities in each Member State and
have safeguarded their right to determine values related to regulatory safety matters at national level
where these continue to vary from State to State.
Status and field of application of Eurocodes
The Member States of the EU and EFTA recognise that Eurocodes serve as reference documents for
the following purposes :
– as a means to prove compliance of building and civil engineering works with the essential
requirements of Council Directive 89/106/EEC, particularly Essential Requirement N°1 –
Mechanical resistance and stability – and Essential Requirement N°2 –Safety in case of fire ;
– as a basis for specifying contracts for construction works and related engineering services ;
– as a framework for drawing up harmonised technical specifications for construction products (ENs
and ETAs)
The Eurocodes, as far as they concern the construction works themselves, have a direct relationship
with the Interpretative Documents referred to in Article 12 of the CPD, although they are of a different
nature from harmonised product standards . Therefore, technical aspects arising from the Eurocodes
work need to be adequately considered by CEN Technical Committees and/or EOTA Working Groups
working on product standards with a view to achieving full compatibility of these technical
specifications with the Eurocodes.
The Eurocode standards provide common structural design rules for everyday use for the design of
whole structures and component products of both a traditional and an innovative nature. Unusual
forms of construction or design conditions are not specifically covered and additional expert
consideration will be required by the designer in such cases.

According to Art. 3.3 of the CPD, the essential requirements (ERs) shall be given concrete form in interpretative documents
for the creation of the necessary links between the essential requirements and the mandates for harmonised ENs and
ETAGs/ETAs.
According to Art. 12 of the CPD the interpretative documents shall :
a) give concrete form to the essential requirements by harmonising the terminology and the technical bases and indicating
classes or levels for each requirement where necessary ;
b) indicate methods of correlating these classes or levels of requirement with the technical specifications, e.g. methods of
calculation and of proof, technical rules for project design, etc. ;
c) serve as a reference for the establishment of harmonised standards and guidelines for European technical approvals.
The Eurocodes, de facto, play a similar role in the field of the ER 1 and a part of ER 2.
National Standards implementing Eurocodes
The National Standards implementing Eurocodes will comprise the full text of the Eurocode (including
any annexes), as published by CEN, which may be preceded by a National title page and National
foreword, and may be followed by a National annex.
The National annex may only contain information on those parameters which are left open in the
Eurocode for national choice, known as Nationally Determined Parameters, to be used for the design
of buildings and civil engineering works to be constructed in the country concerned, i.e. :
– values and/or classes where alternatives are given in the Eurocode,
– values to be used where a symbol only is given in the Eurocode,
– country specific data (geographical, climatic, etc.), e.g. wind map,
– the procedure to be used where alternative procedures are given in the Eurocode.
It may also contain
– decisions on the use of informative annexes, and
– references to non-contradictory complementary information to assist the user to apply the
Eurocode.
Links between Eurocodes and harmonised te
...