ISO 4354:2009

INTERNATIONAL ISO
STANDARD 4354
Second edition
2009-06-01
Wind actions on structures
Actions du vent sur les structures

Reference number
©
ISO 2009
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ii © ISO 2009 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Symbols.2
4 Wind actions .2
5 Wind pressure.3
6 Wind force .3
7 Site peak dynamic pressure.4
8 Exposure factor .4
9 Pressure and force coefficients.4
10 Dynamic response factor.5
11 Criterion for aeroelastic instability .5
12 Methods of determination of wind loads .5
Annex A (normative) Mean velocity method.7
Annex B (informative) Determination of reference wind speed .9
Annex C (informative) Determination of exposure factors .11
Annex D (informative) Aerodynamic pressure and force coefficients .22
Annex E (informative) Dynamic response factors.40
Annex F (informative) Structures subject to critical excitation vortex resonance and aeroelastic
instability.59
Annex G (informative) Mode combinations.62
Annex H (informative) Wind tunnel testing .64
Annex I (informative) Computation-based methods .65
Annex J (informative) Reliability considerations.66
Bibliography.67

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
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International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 4354 was prepared by Technical Committee ISO/TC 98, Bases for design of structures, Subcommittee
SC 3, Loads, forces and other actions.
This second edition cancels and replaces the first edition (ISO 4354:1997), which been technically revised.
iv © ISO 2009 – All rights reserved

Introduction
This International Standard is intended for use by countries without an adequate wind loading standard and as
a bridge between existing International Standards. The data in the annexes, with the exception of Annex A,
whilst formally only informative, and limited to the most common usage, are intended for use within the
definitions in this International Standard. Additional data will be provided from time to time in ISO Technical
Reports for use on the same basis.

INTERNATIONAL STANDARD ISO 4354:2009(E)

Wind actions on structures
1 Scope
This International Standard describes the actions of wind on structures and specifies methods of calculating
characteristic values of wind loads for use in designing buildings, towers, chimneys, bridges and other
structures, as well as their components and appendages. The loads are suitable for use in conjunction with
ISO 2394 and other International Standards concerned with wind loads. In particular, this International
Standard facilitates the conversion between peak and mean wind speed methodologies and covers the three
main storm types, synoptic winds, thunderstorms and tropical cyclones (hurricanes and typhoons).
This International Standard provides the basic methods from which to determine wind loading analytically
through the determination of design pressures or orthogonal along-wind and cross-wind forces and moments
for structures of simple shape and wind directionality effects, and through wind tunnel or computational
determinations of pressure, forces and moments for structures with complex shapes and wind directionality
effects resulting in complex combinations of forces and moments.
Structures of unusual nature, size or complexity (e.g. tall buildings, long span bridges, large span roofs, guyed
masts, offshore and moving structures) typically require a special engineering study; some guidance is given
on the limitations of this International Standard in these cases.
Two methods of analytical determination of design wind loads are given in this International Standard, one
based on a peak velocity and the other on a mean velocity. Both methods can be used when dynamic
response effects are important, and where they are not important only the peak-velocity method is used in this
International Standard by taking the peak dynamic response factor to be unity. To simplify presentation, the
method based on the peak velocity is given in the main body of this International Standard and the method
based on the mean velocity is given in a normative Annex A.
2 Normative references
The following referenced documents are indispensable for the application 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.
ISO 2394, General principles on reliability for structures
3 Symbols
Symbol Term Unit
A Tributary or local area (area of application of pressure coefficient C) m
p
A Reference area for force on overall structure or part of structure m
ref
C Peak dynamic response factor 1
dyn
C Mean dynamic response factor 1
dyn, m
C Peak exposure factor 1
exp
C Mean exposure factor 1
exp, m
C Force coefficient 1
F
C Mean force coefficient 1
Fm
C Pressure coefficient (time and spatially averaged) 1
p
C Standard deviation force coefficient 1
σF
F Peak force N
F Peak force on a tributary or local area N
loc
F Mean force N
m
g Peak factor 1
g Wind speed peak factor 1
v
h Height m
I Wind speed turbulence intensity 1
v
−2
p Pressure Nm
−2
q Regional reference mean dynamic pressure Nm
ref, m
−2
q Site peak dynamic pressure Nm
site
−2
q Site mean dynamic pressure Nm
site, m
−1
V Peak wind speed ms
−1
V Critical wind speed at the top of the structure ms
hcr
−1
V Mean wind speed ms
m
−1
V Regional peak reference wind speed (with return period) ms
ref
−1
V Regional mean reference wind speed ms
ref, m
−1
V Site peak velocity ms
site
−1
V Site mean velocity ms
site, m
σ Standard deviation of force N
F
4 Wind actions
Wind actions that shall be considered in the design of the structure can produce the following:
a) excessive forces or instability in the structure or its structural members or elements;
b) excessive deflection or distortion of the structure or its elements;
c) repeated dynamic forces causing fatigue of structural elements;
2 © ISO 2009 – All rights reserved

d) aeroelastic instability, in which motion of the structure in wind produces aerodynamic forces augmenting
the motion;
e) excessive dynamic movements causing concern or discomfort to occupants or onlookers;
f) effects of interference from existing and potential future buildings.
NOTE Wind pressure and force given in this International Standard are equivalent static wind loads and not pure
external excitations. As the equivalent static wind loads are essentially based on linear elastic building and structure
behaviour, it is necessary to give careful attention if they are applied to design in the plastic region.
5 Wind pressure
For the actions referred to in Clause 4 a), b), c) and e), the effective wind pressure, p, shall be determined
from a relationship incorporating the site dynamic pressure, q , defined in Clause 7 and Clause 8, a
site
pressure coefficient, C , and a dynamic response factor, C , of the general form of Equation (1):
p dyn
p = q × C × C (1)
site p dyn
The wind pressure is assumed to act statically in a direction normal to the surface of the structure or element,
except where tangential frictional forces are specifically identified. Both internal and external pressures shall
be considered. Integration of pressures shall be undertaken to obtain global forces or forces for defined
tributary areas.
The effects of wind from all directions shall be considered.
6 Wind force
For some structures, it may be appropriate to represent the wind forces, F, by their resultants. These
resultants shall include along-wind (drag), cross-wind (lift), torsional and overturning actions. Different
magnitudes and distributions of the wind force can be necessary to evaluate the actions described in
Clause 4 a), b), c) and e).
The derivation of effective wind forces on an element, or resultant forces and moments, shall be determined
by using either the peak reference dynamic pressure given here, or the mean reference dynamic pressure
given in Annex A.
The peak reference pressure method assumes that the dynamic effects can be represented by a maximum or
peak loading effect based on a peak reference pressure combined with a mean pressure coefficient, (or mean
pressure coefficient modified for local effects relating to area of application and statistical characteristics), and
a peak dynamic response factor, C , from the general relationships given in Equations (2) and (3):
dyn
F = q × C × C × A (2)
loc site p dyn
F = q × C × C × A (3)
site F dyn ref
Equation (2) is used for the force on a tributary or local area, A. Equation (3) is used for the total force on the
whole structure or part of the structure. The value of C can be taken as 1,0 except where the structure is

dyn
dynamically wind-sensitive, as described in Annex E.
In many cases total loads on whole structures w
...