FprEN 1991-1-4

SLOVENSKI STANDARD
oSIST prEN 1991-1-4:2024
01-junij-2024
Evrokod 1 - Vplivi na konstrukcije - 1-4. del: Obtežbe vetra
Eurocode 1 - Actions on structures - Part 1-4: Wind actions
Eurocode 1 - Einwirkungen auf Tragwerke - Teil 1-4: Windlasten
Eurocode 1 - Actions sur les structures - Partie 1-4 : Actions du vent
Ta slovenski standard je istoveten z: prEN 1991-1-4
ICS:
91.010.30 Tehnični vidiki Technical aspects
oSIST prEN 1991-1-4:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1991-1-4:2024
oSIST prEN 1991-1-4:2024
DRAFT
EUROPEAN STANDARD
prEN 1991-1-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2024
ICS 91.010.30 Will supersede EN 1991-1-4:2005
English Version
Eurocode 1 - Actions on structures - Part 1-4: Wind actions
Eurocode 1 ¿ Actions sur les structures ¿ Partie 1-4 : Eurocode 1 - Einwirkungen auf Tragwerke - Teil 1-4:
Actions du vent Allgemeine Einwirkungen - Windlasten
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 1991-1-4:2024 E
worldwide for CEN national Members.

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Contents Page
European foreword . 6
0 Introduction . 7
1 Scope . 11
1.1 Scope of prEN 1991-1-4 . 11
1.2 Assumptions . 11
2 Normative references . 11
3 Terms, definitions and symbols . 12
3.1 Terms and definitions . 12
3.2 Symbols . 13
4 Design situations . 18
5 Modelling of wind actions . 19
5.1 Representations of wind actions . 19
5.2 Classification of wind actions . 19
5.3 Characteristic values . 19
5.4 Loading models . 19
5.5 Design assisted by testing and measurements . 23
6 Wind velocity and velocity pressure . 23
6.1 Basis for calculation . 23
6.2 Basic values . 24
6.3 Mean wind velocity and pressure . 25
6.4 Wind turbulence . 29
6.5 Peak wind velocity and velocity pressure . 30
7 Wind actions . 31
7.1 General. 31
7.2 Choice of aerodynamic coefficient . 32
7.3 Wind pressure on surfaces . 32
7.4 Net pressure on surfaces . 33
7.5 Wind forces . 33
8 Structural factor 𝒄𝒄sd . 35
8.1 General. 35
8.2 Approximate determination of 𝒄𝒄sd . 35
8.3 Serviceability assessments . 38
9 Across-wind and torsional actions on buildings . 38
10 Aeroelastic phenomena . 38
10.1 General. 38
10.2 Basis for calculation . 38
10.3 Galloping . 41
10.4 Divergence and flutter . 41
10.5 Wake buffeting . 41
Annex A (informative) This page is left blank intentionally . 42
Editorial Note . 42
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Annex B (informative) Terrain effects . 43
Use of this annex . 43
Scope and field of application . 43
Illustrations of the upper roughness of each terrain category . 43
Transition between terrain categories 0, I, II, III and IV . 44
Orography coefficients . 46
Neighbouring structures . 51
Displacement height . 52
Alternative wind model . 53
Annex C (normative) Pressure coefficients for pressures on surface . 56
Use of this annex . 56
Scope and field of application . 56
Pressure and force coefficients . 56
Pressure coefficients for rectangular plan buildings . 57
Pressure coefficients for irregular buildings . 84
Pressure coefficients for circular structures . 89
Internal pressures . 101
Annex D (normative) Net pressure and force coefficients for walls, roofs and skins . 104
Use of this annex . 104
Scope and field of application . 104
Net pressure and force coefficients for canopy roofs, porches and balconies . 104
Net pressure coefficients for free-standing walls, parapets, fences and signboards . 115
Annex E (normative) Force coefficients for structures and structural members . 121
Use of this annex . 121
Scope and field of application . 121
General . 121
Force coefficients for spheres . 130
Force coefficients for square and triangular lattice structures and scaffoldings . 132
Force coefficients for flags . 141
Force coefficients for iced structures . 142
Force coefficients for bridge decks . 146
Friction coefficients . 155
Annex F (informative) Procedure for along-wind dynamic response . 157
Use of this annex . 157
Scope and field of application . 157
Along-wind dynamic response . 157
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Along-wind turbulence . 157
Constant sign mode shapes . 159
Background response factor . 166
Resonance response factor . 168
Peak factor for resonant response . 170
Non-constant sign mode shapes — Calculation of equivalent static wind force . 171
Number of loads for dynamic response . 175
Annex G (informative) Procedure for across-wind and torsional actions on susceptible buildings
.......................................................................................................................................................................... 177
Use of this annex . 177
Scope and field of application . 177
General. 177
Detailed procedure for across-wind actions . 178
Detailed procedure for torsional actions . 182
Simplified procedure for across-wind and torsional actions for square plan buildings . 185
Across-wind and torsional accelerations . 187
Combination of actions and action effects . 188
Annex H (informative) Procedure for across-wind dynamic and aeroelastic response of slender
structures. 190
Use of this annex . 190
Scope and field of application . 190
General. 190
Across-wind dynamic response . 191
Vortex shedding . 198
Galloping . 210
Divergence and flutter . 214
Annex I (informative) Dynamic characteristics of structures with linear elastic behaviour . 219
Use of this annex . 219
Scope and field of application . 219
General. 219
Fundamental frequency . 219
Fundamental mode shape . 226
Equivalent mass. 229
Logarithmic decrement of damping . 229
Annex J (informative) Response of steel lattice towers and guyed masts . 232
Use of this annex . 232
Scope and field of application . 232
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General . 232
Response of lattice towers . 232
Response of guyed masts . 237
Annex K (informative) Guidance on derivation of design parameters from wind tunnel tests and
numerical simulations . 247
Use of this annex . 247
Scope and field of application . 247
General . 247
Derivation of design parameters from wind tunnel tests . 248
Derivation of design parameters from numerical simulations . 256
Annex L (informative) Guidance on derivation of wind speeds from measurements at
meteorological stations . 261
Use of this annex . 261
Scope and field of application . 261
Wind Speed Records . 261
Extreme Value or Parent Population Analysis . 262
Annex M (informative) Guidance on probabilistic description of wind actions . 263
Use of this annex . 263
Scope and field of application . 263
Probabilistic variables . 263
Calibration of the values of the terms on basis of their statistical distribution . 264
Bibliography . 265

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European foreword
This document (prEN 1991-1-4:2024) has been prepared by Technical Committee CEN/TC 250
“Structural Eurocode”, 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 1991-1-4:2005 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 structure
— 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 Eurocodes under development, e.g. Eurocode for design of structural glass
The Eurocodes are intended for use by designers, clients, manufacturers, constructors, relevant
authorities (in exercising their duties in accordance with national or international regulations),
educators, software developers, and committees drafting standards for related product, testing and
execution standards.
NOTE Some aspects of design are most appropriately specified by relevant authorities or, where not specified,
can be agreed on a project-specific basis between relevant parties such as designers and clients. The Eurocodes
identify such aspects making explicit reference to relevant authorities and relevant parties.
0.2 Introduction to EN 1991 (all parts)
EN 1991 specifies actions for the structural design of buildings, bridges and other civil engineering works,
or parts thereof, including temporary structures, in conjunction with EN 1990 and the other Eurocodes.
EN 1991 does not cover the specific requirements of actions for seismic design. Provisions related to such
requirements are given in EN 1998 (all parts), which complement and are consistent with EN 1991.
EN 1991 is also applicable to existing structures for their:
— structural assessment,
— strengthening or repair,
— change of use.
NOTE In these cases, additional or amended provisions can be necessary.
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EN 1991 is applicable for the design of structures where materials or actions outside the scope of the
other Eurocodes are involved.
NOTE In this case, additional or amended provisions can be necessary.
EN 1991 is subdivided in various parts:
 EN 1991-1-1, Eurocode 1 — Actions on structures — Part 1-1: Specific weight of materials, self-weight
of construction works and imposed loads for buildings
 EN 1991-1-2, Eurocode 1 — Actions on structures — Part 1-2: Actions on structures exposed to fire
 EN 1991-1-3, Eurocode 1 — Actions on structures — Part 1-3: Snow Loads
 EN 1991-1-4, Eurocode 1 — Actions on structures — Part 1-4: Wind Actions
 EN 1991-1-5, Eurocode 1 — Actions on structures — Part 1-5: Thermal Actions
 EN 1991-1-6, Eurocode 1 — Actions on structures — Part 1-6: Actions during execution
 EN 1991-1-7, Eurocode 1 — Actions on structures — Part 1-7: Accidental actions
 EN 1991-1-8, Eurocode 1 — Actions on structures — Part 1-8: Actions from waves and currents on
coastal structures
 EN 1991-1-9, Eurocode 1 — Actions on structures — Part 1-9: Atmospheric icing
 EN 1991-2, Eurocode 1 — Actions on structures — Part 2: Traffic loads on bridges and other civil
engineering works
 EN 1991-3, Eurocode 1 — Actions on structures — Part 3: Actions induced by cranes and machines
 EN 1991-4, Eurocode 1 — Actions on structures — Part 4: Silos and tanks
0.3 Introduction to prEN 1991-1-4
prEN 1991-1-4 gives design guidance and actions for the structural design of buildings and civil
engineering works for wind.
prEN 1991-1-4 is intended to be used with EN 1990, the other Parts of EN 1991 and EN 1992 to EN 1999
for the design of structures.
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 1991-1-4
National choice is allowed by this standard where explicitly stated within notes. National choice includes
the selection of values for Nationally Determined Parameters (NDPs).
The national standard implementing prEN 1991-1-4 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 choice is given in this standard, the choice can be
specified by the relevant authority or, where not specified, agreed for a specific project by the relevant
parties.
National choice is allowed in prEN 1991-1-4 through notes to the following clauses:
5.4(8) 6.1(3) 6.2(1) 6.2(2)
6.2(4) 6.2(5) 6.3.1(1) 6.3.2(1)
6.3.2(3) 6.3.3(2) 6.4(2) 6.4(3)
6.4(4) 6.5(1) 7.1(2) 9(1)
B.1(1) B.3(1) B.4.1(2) B.4.3(5)
B.5(5) B.8.1(1) B.8.2(1) Table B.3 (NDP)
B.8.3(2) C.3.1(1) C.3.2(1) C.4.1(4)
C.4.1(6) C.4.2(6) C.4.3(3) Table C.3 (NDP)
C.4.4(3) C.4.4(4) C.4.5(3) C.4.5(4)
C.4.6(3) C.4.8(1) C.4.9(2) C.4.9(3)
C.5.1(2) C.5.2(1) C.5.3(1) C.6.1.1(1)
C.6.1.1(4) C.6.2(1) C.6.3(1) C.7(7)
D.3.2(1) D.3.3(1) D.3.6(1) D.4.2(1)
D.4.3(1) E.3.1(3) E.3.3(1) E.3.4(1)
E.3.5(1) E.3.5(2) E.3.5(7) E.3.6(1)
E.3.7(1) E.4(1) E.5.1(1) E.5.1(3)
E.5.6(1) E.7.1(1) E.8.1(1) E.8.1(4)
E.8.1(5) E.8.2(1) E.8.2.2(4) E.8.2.3(1)
E.8.2.4(3) E.8.2.5(1) F.1(1) F.5.3(2)
F.9.2(1) G.1(1) G.3(2) H.1(1)
H.3(4) H.5.3.2(1) H.5.3.4(1) H.5.4(2)
H.5.5.1(1) H.5.5.2(2) H.5.5.2(3) H.5.6.1(1)
H.5.6.2(1) H.5.6.3(1) H.6.4(2) I.1(1)
J.1(1) J.4.2.8(4) J.4.3(1) J.4.3(2)
J.5.3.2.2(2) J.5.3.2.3(1) J.5.3.2.8(4) K.1(1)

L.1(1) M.1(1)
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National choice is allowed in prEN 1991-1-4 on the application of the following informative annexes:
Annex B Annex F Annex G Annex H
Annex I Annex J Annex K Annex L
Annex M
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 prEN 1991-1-4
(1) This document gives principles and rules for the determination of natural wind actions for the
structural design of building and civil engineering works for each of the loaded areas under consideration.
This includes the whole structure or parts of the structure or elements attached to the structure, e.g.
components, cladding units and their fixings, safety and noise barriers.
(2) This part is applicable to:
— buildings and civil engineering works with heights up to 300 m;
— bridges having no span greater than 200 m.
(3) This part is intended to predict characteristic wind actions on land-based structures, their
components and appendages.
(4) This part is also applicable to structures less than 1 km offshore from the main coastline. For
offshore structures more than 1 km from the main coastline, the terrain effects defined in this part do not
apply.
(5) This part does not give guidance on non-synoptic winds (e.g. thunderstorms, downbursts,
microbursts, tornadoes, etc.), mixed wind climates, nor does it give guidance on how to account for local
effects (e.g. thermal effects, funnelling, strong arctic thermal surface inversion, etc.).
(6) This document addresses simplified procedures for dynamic effects, mostly based on the
assumption of a dominant single-mode response. General criteria for performing a full dynamic analysis
under aerodynamic excitation are not treated in this document.
(7) Wind pressure effects of passing vehicles are outside the scope of this document.
NOTE See EN 1991-2 for wind effects from passing trains.
1.2 Assumptions
(1) The assumptions given in EN 1990:2023, 1.2 apply.
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.
NOTE See the Bibliography for a list of other documents cited that are not normative references, including
those referenced as recommendations (i.e. in ‘should’ clauses), permissions (‘may’ clauses), possibilities ('can'
clauses), and in notes.
EN 1990, Eurocode — Basis of structural and geotechnical design
ISO 2394, General principles on reliability for structures
ISO 3898, Bases for design of structures — Names and symbols of physical quantities and generic quantities
ISO 8930, General principles on reliability for structures — Vocabulary
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3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1990, ISO 2394, ISO 3898 and
ISO 8930 and the following apply.
3.1.1
fundamental basic wind velocity
characteristic 10-minute mean wind velocity with an annual probability of being exceeded of 0,02,
irrespective of wind direction and time of year, at a height of 10 m above ground level in flat open country
terrain with large windward fetch of low vegetation such as grass and isolated obstacles with separations
of at least 20 obstacle heights, and accounting for altitude effects (if required)
Note 1 to entry: This terrain corresponds to terrain category II in Table 6.1 and is illustrated in B.1.
3.1.2
basic wind velocity
fundamental basic wind velocity modified to account for the annual probability of exceedance, the
direction of the wind, the season and the altitude (if required)
3.1.3
mean wind velocity
basic wind velocity modified to account for the effect of terrain roughness, orography and height above
ground level
3.1.4
peak factor for turbulence
factor corresponding to a gust duration of approximately 3 seconds, which corresponds to standardized
gust durations at meteorological stations
3.1.5
pressure coefficient
coefficient which gives the pressure on the surfaces of buildings or civil engineering works; external
pressure coefficients apply to the external surfaces; internal ones to the internal surfaces
3.1.6
net pressure coefficient
coefficient that accounts for the resulting pressure difference across a skin
3.1.7
force coefficient
coefficient that accounts for the overall effect or the effect per unit length of the wind on a structure,
structural element or component, including friction, if not specifically excluded
3.1.8
friction coefficient
coefficient that accounts for the effects of wind friction on the external surfaces of buildings and
structures
3.1.9
background response factor
factor to allow for the lack of full correlation of the pressure on the structural surfaces
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3.1.10
resonance response factor
factor to allow for the amplification of effects of wind turbulence at the natural frequency of the relevant
vibration mode
3.2 Symbols
(1) For the purposes of this document, the following symbols apply.
NOTE The notation used is based on ISO 3898. In this part the symbol dot in Formulae indicates the
multiplication sign. This notation has been employed to avoid confusion with functional Formulae.
(2) A basic list of notations is provided in EN 1990:2023, 1.6; the additional notations below are
specific to prEN 1991-1-4.
3.2.1 Latin upper case letters
𝐴𝐴 area
𝐴𝐴 area swept by the wind
fr
𝐴𝐴 reference area
ref
𝐴𝐴 base area
shed
𝐵𝐵 background response factor
𝐶𝐶 wind load factor for bridges
𝐸𝐸 Young’s modulus
𝐹𝐹 resultant friction force
fr
𝐹𝐹 vortex exciting force at point j of the structure
𝑗𝑗
𝐹𝐹 resultant wind force
w
𝐻𝐻 height of a topographic feature
turbulence intensity
𝐼𝐼
𝑢𝑢
𝐾𝐾 mode shape factor; shape parameter; factor
𝐾𝐾 aerodynamic damping parameter
a
𝐾𝐾 interference factor for vortex shedding
iv
𝐾𝐾 reduction factor for parapets
rd
𝐾𝐾 load distribution factor
𝑅𝑅,L
𝐾𝐾 correlation length factor
w
𝐾𝐾 non dimensional coefficient
x
𝐿𝐿 length of the span of a bridge deck; turbulent length scale; projected length, chord length
𝐿𝐿 actual length of a leeward slope
d
effective length of a windward slope
𝐿𝐿
e
𝐿𝐿
correlation length
j
𝐿𝐿 actual length of a windward slope
u
𝑁𝑁 number of cycles caused by vortex shedding; number
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𝑁𝑁
number of loads for gust response
g
𝑃𝑃 member force
𝑄𝑄 parameter
𝑅𝑅 wind resistance
𝑅𝑅 resonant response factor
𝑅𝑅𝑅𝑅 Reynolds number
𝑆𝑆 wind action; load effect
𝑆𝑆𝑆𝑆 Scruton number
𝑆𝑆 non-dimensional power spectral density function for along-wind turbulence
𝑢𝑢
𝑆𝑆 non-dimensional power spectral density function for lateral wind turbulence
𝑣𝑣
𝑆𝑆 non-dimensional power spectral density function for vertical wind turbulence
𝑤𝑤
𝑆𝑆𝑆𝑆 Strouhal number
𝑇𝑇 return period
𝑊𝑊 weight of the structural parts contributing to the stiffness of a chimney
s
𝑊𝑊 total weight of a chimney
t
3.2.2 Latin lower case letters
𝑎𝑎 factor of galloping instability
G
𝑎𝑎 combined stability parameter for interference galloping
IG
𝑎𝑎 along-wind peak acceleration
p,𝑥𝑥
𝑏𝑏 width of the structure (the length of the surface perpendicular to the wind direction if
not otherwise specified)
𝑆𝑆 altitude factor
alt
𝑆𝑆 dynamic factor
d
𝑆𝑆 directional factor
dir
𝑆𝑆 exposure factor
e
𝑆𝑆 force coefficient
f
𝑆𝑆 force coefficient of structures or structural elements without free-end flow
f,o
𝑆𝑆 lift force coefficient
f,l
𝑆𝑆 across-wind force coefficient
f,cw
𝑆𝑆 friction coefficient
fr
𝑆𝑆 force coefficient in the across-wind plane
L
𝑆𝑆 moment coefficient
M
𝑆𝑆 pressure coefficient
p
𝑆𝑆 external pressure coefficient
pe
𝑆𝑆 external local pressure coefficient
pe,1
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𝑆𝑆 external detailed pressure coefficient
pe,10
𝑆𝑆 external global pressure coefficient
pe,G
𝑆𝑆 internal pressure coefficient
pi
𝑆𝑆 net pressure coefficient
p,net
𝑆𝑆 probability factor
prob
𝑆𝑆 roughness factor
r
𝑆𝑆 orography factor
o
𝑆𝑆 size factor
s
𝑆𝑆 structural factor
sd
𝑆𝑆 seasonal factor
season
𝑑𝑑 depth of the structure (the length of the surface parallel to the wind direction if not
otherwise specified)
𝑅𝑅 eccentricity of a force or edge distance
𝑓𝑓 non dimensional frequency
L
ℎ height of the structure
ℎ obstruction height
ave
ℎ displacement height
dis
𝑘𝑘 equivalent roughness
𝑘𝑘 peak factor background turbulence
𝐵𝐵
𝑘𝑘 turbulence factor
I
𝑘𝑘 peak factor resonance turbulence
𝑅𝑅
terrain factor
𝑘𝑘
r
𝑘𝑘 peak factor for turbulent wind
𝑢𝑢
𝑘𝑘 torsional stiffness
θ
𝑙𝑙 length of a horizontal structure
𝑚𝑚 mass per unit length
𝑚𝑚 equivalent mass per unit length
𝑛𝑛 natural frequency of the structure of the mode 𝑖𝑖
𝑖𝑖
𝑛𝑛 fundamental frequency of along-wind vibration
1,𝑥𝑥
𝑛𝑛 fundamental frequency of across-wind vibration
1,𝑦𝑦
𝑛𝑛 fundamental frequency of vertical vibration
1,𝑧𝑧
𝑛𝑛 ovalling frequency
o
𝑝𝑝 annual probability of exceedance
𝑞𝑞 reference mean (basic) velocity pressure
b
𝑞𝑞 mean velocity pressure
m
oSIST prEN 1991-1-4:2024
prEN 1991-1-4:2024 (E)
𝑞𝑞 peak velocity pressure
p
𝑟𝑟 radius
𝑠𝑠 factor; coordinate
𝑆𝑆 time
𝑣𝑣 onset wind velocity for galloping
CG
𝑣𝑣 critical wind velocity for interference galloping
CIG
𝑣𝑣 critical wind velocity of vortex shedding
crit
𝑣𝑣 divergence wind velocity
div
𝑣𝑣 mean wind velocity
m
𝑣𝑣 fundamental value of the basic wind velocity
b,0
𝑣𝑣 basic wind velocity
b
𝑤𝑤 wind pressure
𝑥𝑥 horizontal distance in direction of the wind
𝑥𝑥-direction horizontal direction, perpendicular to the span
𝑦𝑦-direction horizontal direction along the span
𝑦𝑦 maximum across-wind amplitude at critical wind speed
max
𝑧𝑧 height above ground
𝑧𝑧 average height
ave
𝑧𝑧-direction vertical direction
𝑧𝑧 roughness length
𝑧𝑧 , 𝑧𝑧 reference height for external wind action, internal pressure
e i
𝑧𝑧 distance from the ground to the considered component
g
𝑧𝑧 maximum height
max
𝑧𝑧 minimum height
min
𝑧𝑧 reference height for determining the structural factor
s
3.2.3 Greek upper case letters
𝛷𝛷 windward slope
𝛷𝛷 fundamental along-wind modal shape
1,𝑥𝑥
𝛷𝛷 fundamental along-wind modal shape of mode 𝑖𝑖
𝑖𝑖,𝑥𝑥
3.2.4 Greek lower case letters
𝛼𝛼 galloping instability parameter
G
𝛼𝛼 combined stability parameter of interference galloping
IG
𝛽𝛽 critical wind direction
k
𝜒𝜒 one-dimensional admittance function
oSIST prEN 1991-1-4:2024
prEN 1991-1-4:2024 (E)
𝛿𝛿 logarithmic decrement of damping
𝛿𝛿 logarithmic decrement of aerodynamic damping
a
𝛿𝛿 logarithmic decrement of damping due to special devices
d
𝛿𝛿 logarithmic decrement of structural damping
s
𝜀𝜀 coefficient
𝜀𝜀 bandwidth factor
𝜀𝜀 frequency factor
𝜂𝜂 variable
𝜑𝜑 solidity ratio, blockage of canopy
𝜆𝜆 slenderness ratio
𝜇𝜇 opening ratio, permeability of a skin
𝜈𝜈 up-crossing frequency; Poisson ratio; kinematic viscosity
𝜃𝜃 torsional angle; wind direction; angle of wind incidence to the normal in plane; slope
𝜌𝜌 air density, which depends on the altitude, temperature and barometric pressure to be
expected in the region during the relevant wind conditions
𝜎𝜎 standard deviation of the along-wind turbulence
𝑢𝑢
𝜎𝜎 standard deviation of the lateral wind turbulence
𝑣𝑣
𝜎𝜎 standard deviation of the vertical wind turbulence
𝑤𝑤
𝜓𝜓 angle of wind incidence to the longitudinal axis
𝜓𝜓 reduction factor for multibay canopies
mc
𝜓𝜓 reduction factor of force coefficient for square sections with rounded corners
r
𝜓𝜓 reduction factor of force coefficient for structural elements with end-effects
λ
𝜓𝜓 end-effect factor for circular cylinders
λα
𝜓𝜓 shelter factor for walls and fences
s
𝜁𝜁 exponent of mode shape
3.2.5 Indices
𝐴𝐴 ancillary item
𝐶𝐶 cable
𝑆𝑆 circular-section members
crit critical
e external; exposure; effective
F face
f flat-sided members
fr friction
G guy
H mast height
oSIST prEN 1991-1-4:2024
prEN 1991-1-4:2024 (E)
𝑖𝑖 internal; mode number
𝑗𝑗 current number of incremental area or point of a structure
M bare mast or mast only
m mean; mast
n single frame
p peak; parapet; combined effects of patch loads
PL patch load
ref reference
S structure
𝑠𝑠 structural scaling factor

sup super-critical
T bare tower or only tower
𝑆𝑆 mean and gust wind
𝑢𝑢 wind velocity in along-wind direction
𝑣𝑣 wind velocity in lateral wind direction
W in the direction of the wind
𝑤𝑤 wind velocity in vertical direction; with wind
𝑖𝑖 in the across-wind direction
𝑥𝑥 along-wind direction; in the across-wind direction
𝑦𝑦 lateral wind direction
Z in the vertical direction
𝑧𝑧 vertical direction; height above ground level
θ angle of wind incidence
...