ISO 3010:2001

Basis for design of structures - Seismic actions on structures

Bases du calcul des constructions — Actions sismiques sur les structures

General Information

• Status: Withdrawn
• Publication Date: 19-Dec-2001
• Withdrawal Date: 19-Dec-2001
• ICS: 91.080.01 - Structures of buildings in general
• ICS: 91.120.25 - Seismic and vibration protection
• Technical Committee: ISO/TC 98/SC 3 - Loads, forces and other actions
• Drafting Committee: ISO/TC 98/SC 3 - Loads, forces and other actions
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 30-Mar-2017
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 3010:2017 - Bases for design of structures - Seismic actions on structures
• Effective Date: 08-Dec-2012
• Revises: ISO 3010:1988 - Bases for design of structures - Seismic actions on structures
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 3010
Second edition
2001-12-01
Basis for design of structures — Seismic
actions on structures
Bases du calcul des constructions — Actions sismiques sur les structures
Reference number
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Contents Page
1 Scope . 1
2 Normative reference . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Bases of seismic design . 3
6 Principles of seismic design . 4
7 Principles of evaluating seismic actions . 5
8 Evaluation of seismic actions by equivalent static analysis . 7
9 Evaluation of seismic actions by dynamic analysis . 9
10 Estimation of paraseismic influences . 11
Annexes
A Load factors as related to the reliability of the structure, seismic hazard zoning factor and representative
values of earthquake ground motion intensity. 12
B Structural factor. 15
C Normalized design response spectrum. 17
D Seismic force distribution factor and seismic shear distribution factor. 19
E Components of seismic action . 22
F Torsional moments . 24
G Dynamic response. 26
H Damping ratio. 30
I Response control systems . 31
J Paraseismic influences. 35
Bibliography. 36
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ISO 2001 – All rights reserved iii

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 non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the 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 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an 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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 3010 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 3010:1988), which has been technically revised.
Annexes A, B, C, D, E, F, G, H, I and J of this International Standard are for information only.
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Introduction
This International Standard presents basic principles for the evaluation of seismic actions on structures. The seismic
actions described are fundamentally compatible with ISO 2394.
It also includes principles of seismic design, since the evaluation of seismic actions on structures and the design of
the structures are closely related.
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ISO 2001 – All rights reserved v

INTERNATIONAL STANDARD ISO 3010:2001(E)
Basis for design of structures — Seismic actions on structures
1 Scope
This International Standard specifies principles of evaluating seismic actions for the seismic design of buildings,
towers, chimneys and similar structures. Some of the principles can be referred to for the seismic design of structures
such as bridges, dams, harbour installations, tunnels, fuel storage tanks, chemical plants and conventional power
plants.
The principles specified in this International Standard do not cover nuclear power plants, since these are dealt with
separately in other International Standards.
In regions where the seismic hazard is low, methods of design for structural integrity may be used in lieu of methods
based on a consideration of seismic actions.
This International Standard is not a legally binding and enforceable code. It can be viewed as a source document that
is utilized in the development of codes of practice by the competent authority responsible for issuing structural design
regulations.
NOTE 1 This International Standard has been prepared mainly for engineered structures. The principles are, however,
applicable to non-engineered structures.
NOTE 2 The qualification of the level of seismic hazard that would be considered low depends on not only the seismicity of the
region but other factors, including types of construction, traditional practices, etc. Methods of design for structural integrity include
regional design horizontal forces which provide a measure of protection against seismic actions.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent edition of the normative document indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 2394, General principles on reliability for structures
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
complete quadratic combination method
method to evaluate the maximum response of a structure by the quadratic combination of modal response values
3.2
ductility
ability to deform beyond the elastic limit under cyclic loadings without serious reduction in strength or energy
absorption capacity
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3.3
liquefaction
loss of shear strength and degradation of stiffness under cyclic loadings in saturated, loose, cohesionless soils
3.4
moderate earthquake ground motion
moderate ground motion caused by earthquakes which may be expected to occur at the site during the service life of
the structure
3.5
normalized design response spectrum
spectrum to determine the base shear factor relative to the maximum ground acceleration as a function of the
fundamental natural period of the structure
3.6
paraseismic influences
ground motion whose characteristics are similar to those of natural earthquake ground motions, but its sources are
mainly due to human activities
3.7
P-delta effect
second-order effect which is caused by the additional moment due to the large displacement and the gravity load
3.8
restoring force
force exerted from the deformed structure or structural elements which tends to move the structure or structural
elements to the original position
3.9
seismic force distribution factor of theith level
k
F,i
factor to distribute the seismic shear force of the base to theith level, which characterizes the distribution of seismic
forces in elevation, where
X
k = 1
F,i
3.10
seismic hazard zoning factor
k
Z
factor to express the relative seismic hazard of the region
NOTE This is usually unity at the region of the highest seismic hazard.
3.11
seismic shear distribution factor of theith level
k
v,i
ratio of the seismic shear factor of the ith level to the seismic shear factor of the base, which characterizes the
distribution of seismic shear forces in elevation
NOTE k = 1 at the base and usually becomes largest at the top.
v,i
3.12
severe earthquake ground motion
severe ground motion caused by an earthquake that could occur at the site
3.13
square root of sum of squares method
method to evaluate the maximum response of a structure by the square root of the sum of the squares of modal
response values
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3.14
structural factor
k
D
factor to reduce design seismic forces or shear forces taking into account ductility, acceptable deformation, restoring
force characteristics and overstrength (or overcapacity) of the structure
4 Symbols and abbreviated terms
CQC Complete quadratic combination
F Design lateral seismic force of theith level of a structure for SLS
E,s,i
F Design lateral seismic force of theith level of a structure for ULS
E,u,i
F Gravity load at theith level of the structure
G,i
k Structural factor
D
k Representative value of earthquake ground motion intensity for SLS
E,s
k Representative value of earthquake ground motion intensity for ULS
E,u
k Seismic force distribution factor of theith level
F,i
k Ordinate of the normalized design response spectrum
R
k Seismic shear distribution factor of theith level
v,i
k Seismic hazard zoning factor
Z
n Number of levels above the base
SLS Serviceability limit state
SRSS Square root of sum of squares
ULS Ultimate limit state
V Design lateral seismic shear force of theith level of a structure for SLS
E,s,i
V Design lateral seismic shear force of theith level of a structure for ULS
E,u,i
Load factor as related to reliability of the structure for SLS
E,s
Load factor as related to reliability of the structure for ULS
E,u
5 Bases of seismic design
The basic philosophy of seismic design of structures is, in the event of earthquakes,
— to prevent human casualties,
— to ensure continuity of vital services, and
— to minimize damage to property.
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It is recognized that to give complete protection against all earthquakes is not economically feasible for most types of
structures. This International Standard states the following basic principles.
a) The structure should not collapse nor experience other similar forms of structural failure due to severe
earthquake ground motions that could occur at the site (ultimate limit state: ULS).
b) The structure should withstand moderate earthquake ground motions which may be expected to occur at the site
during the service life of the structure with damage within accepted limits (serviceability limit state: SLS).
In order to ensure safety and vital services, elements controlling services to buildings, such as cables, pipe lines, air-
conditioning, fire-fighting system, elevator system and other similar systems, should be protected against seismic
actions.
NOTE 1 In addition to the seismic design and construction of structures stated in this International Standard, it is useful to
consider adequate countermeasures against secondary disasters such as fire, leakage of hazardous materials from industrial
facilities or storage tanks, and large-scale landslides which may be triggered by the earthquake.
NOTE 2 Following an earthquake, earthquake-damaged buildings may need to be evaluated for safe occupation during a period
of time when aftershocks occur. This International Standard, however, does not address actions that can be expected due to
aftershocks. In this case a model of the damaged structure is required to evaluate seismic actions.
6 Principles of seismic design
6.1 Construction site
Characteristics of construction sites under seismic actions should be evaluated, taking into account microzonation
criteria (vicinity to active faults, soil profile, soil behaviour under large strain, liquefaction potential, topography,
subsurface irregularity, and other factors such as interactions between these).
6.2 Structural configuration
For better seismic resistance, it is recommended that structures have simple forms in both plan and elevation.
a) Plan irregularities
Structural elements to resist horizontal seismic actions should be arranged such that torsional effects become as
small as possible. Irregular shapes in plan causing eccentric distribution of forces are not desirable, since they
produce torsional effects which are difficult to assess accurately and which may amplify the dynamic response of
the structure (see annex F).
b) Vertical irregularities
Changes in mass, stiffness and capacity along the height of the structure should be minimized to avoid damage
concentration (see annex D).
When a structure with complex form is to be designed, an appropriate dynamic analysis is recommended in order to
check the potential behaviour of the structure.
6.3 Influence of non-structural elements
The building, including non-structural as well as structural elements, should be clearly defined as a lateral load-
resisting system which can be analysed. In computing the earthquake response of a building, the influence of not
only the structural frames but also walls, floors, partitions, stairs, windows, etc., should be considered.
NOTE Non-structural elements neglected in seismic analysis can provide additional strength and stiffness to the structure, which
may result in favourable behaviour during earthquakes. The non-structural elements, however, may cause unfavourable
behaviour, e.g. spandrel walls may reduce clear height of reinforced concrete columns and cause the brittle shear failure to the
columns, or unsymmetrical allocation of partition walls (which are considered to be non-structural elements) may cause large
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torsional moments to the structure. Therefore, all elements should be considered as they behave during earthquakes. If neglecting
the non-structural elements does not cause any unfavourable behaviour, they need not be included in seismic analysis.
6.4 Strength and ductility
The structural system and its structural elements (both members and connections) should have both adequate
strength and ductility for the applied seismic actions.
The structure should have adequate strength for the applied seismic actions and sufficient ductility to ensure
adequate energy absorption (see annex B). Special attention should be given to suppressing the brittle behaviour of
structural elements, such as buckling, bond failure, shear failure, and brittle fracture. The deterioration of the
restoring force under cyclic loadings should be taken into account.
Local capacities of the structure may be higher than that assumed in the analysis. Such overcapacities should be
taken into account in evaluating the behaviour of the structure, including the failure mode of structural elements,
failure mechanism of the structure, and the behaviour of the foundations due to severe earthquake ground motions.
6.5 Deformation of the structure
The deformation of the structure under seismic actions should be limited, neither causing malfunction of the structure
for moderate earthquake ground motions, nor causing collapse or other similar forms of structural failure for severe
earthquake ground motions.
NOTE There are two kinds of deformations to be controlled: the interstorey drift which is the lateral displacement within a storey
and the total lateral displacement at some level relative to the base. The interstorey drift should be limited to restrict damage to
non-structural elements such as glass panels, curtain walls, plaster walls and other partitions for moderate earthquake ground
motions and to control failure of structural elements and the instability of the structure in the case of severe earthquake ground
motions. The control of the total displacement is concerned with sufficient separations of two adjoining structures to avoid
damaging contact for severe earthquake ground motions. The control of the total displacement may also decrease the amplitude
of vibration of the structure and reduce panic or discomfort for moderate earthquake ground motions. In the evaluation of
deformations under severe earthquake ground motions, it is generally necessary to account for the second order effect (P-delta
effect) of additional moments due to gravity plus vertical seismic forces acting on the displaced structure which occurs as a result
of severe earthquake ground motions.
6.6 Response control systems
Response control systems for structures, e.g. seismic isolation, can be used to ensure continuous use of the
structure for moderate earthquake ground motions and to prevent collapse during severe earthquake ground motions
(see annex J).
6.7 Foundations
The type of foundation should be selected carefully in accordance with the type of structure and local soil conditions,
e.g. soil profile, subsurface irregularity, groundwater level. Both forces and deformations transferred through the
foundations should be evaluated properly considering the strains induced to soils during earthquake ground motions
as well as kinematic and inertial interactions between soils and foundations.
7 Principles of evaluating seismic actions
7.1 Variable and accidental actions
Seismic actions shall be taken either as variable actions or accidental actions.
Structures should be verified against design values of seismic actions for ULS and SLS. The verification for the SLSs
may be omitted provided that it is satisfied through the verification for the ULSs (see 8.1).
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Accidental seismic actions can be considered for structures in regions where seismic activity is low to ensure
structural integrity.
NOTE Verification of the SLS may be omitted in low seisimicity regions, where the SLS actions are low, and for stiff structures
(e.g. shear wall buildings) which are designed to remain nearly elastic under ULS actions.
7.2 Dynamic and equivalent static analyses
The seismic analysis of structures shall be performed either by dynamic analysis or by equivalent static analysis. In
both cases the dynamic properties of the structure shall be taken into consideration.
Appropriate post-elastic performance shall be provided by adequate choice of the structural system and ductile
detailing. The sequence of behaviour of the structure, including the formation of the collapse mechanism, should be
established.
NOTE 1 Usually the sequence of behaviour can be verified through non-linear static analysis under lateral loads.
a) Dynamic analysis
A dynamic analysis is highly recommended for specific structures such as slender high-rise buildings and
structures with irregularities of geometry, mass distribution or stiffness distribution. A dynamic analysis is also
recommended for structures with innovative structural systems (e.g. response control systems, see 6.6),
structures made of new materials, structures built on special soil conditions, and structures of special
importance.
b) Equivalent static analysis
Ordinary and regular structures may be designed by the equivalent static method using conventional linear
elastic analysis.
NOTE 2 If it is essential that services (e.g. mechanical and electrical equipment and pipings) retain their functions during and
after severe or moderate earthquake ground motions, then the design of these services should preferably be done by dynamic
analysis procedures based on the earthquake response of the structure which supports them.
7.3 Criteria for determination of seismic actions
The design seismic actions shall be determined based on the following considerations.
a) Seismicity of the region
The seismicity of the region where a structure is to be constructed is usually indicated by a seismic zoning map,
which may be based on either the seismic history or on seismotectonic data of the region, or on a combination of
historical and seismotectonic data. In addition, the expected values of the maximum intensity of the earthquake
ground motion in the region in a given future period of time should be determined on the basis of the regional
seismicity.
NOTE 1 In addition to the consideration of the historical records of earthquakes, investigation of actual earthquake faults in
the region could provide valuable guidance for estimating the future occurrence of earthquakes.
NOTE 2 There exist many kinds of parameters which can be used to characterize the intensity of earthquake ground motion.
These are seismic intensity scales, peak ground acceleration and velocity, “effective” peak ground acceleration and velocity
which is related to smoothed response spectra, input energy, etc. Recently a method has been proposed to determine the
parameters from a probabilistic seismic hazard analysis to give uniform hazard for structures of different periods of vibration.
The selection of the type of parameter depends mainly on available data and the type of structure.
b) Soil conditions
Dynamic properties of the supporting soil layers of the structure should be investigated and considered.
NOTE 3 The ground motion at a particular site during earthquakes has a predominant period of vibration which, in general,
is shorter on firm ground and longer on soft ground. Attention should be paid to the possibility of local amplifications of
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earthquake ground motions, which may occur (inter alia) in the presence of soft soils and near the edge of alluvial basins. The
possibility of liquefaction should also be considered, particularly in saturated, loose, cohesionless soils.
NOTE 4 The properties of earthquake ground motions such as predominant periods of vibration and duration of motion are
also important features as far as the destructiveness of earthquakes is concerned. Furthermore, it should be recognized that
structures constructed on soft ground often suffer damage due to uneven or large settlements during earthquakes.
c) Dynamic properties of the structure
Dynamic properties, such as periods and modes of vibration and damping properties, should be considered for
the overall soil-structure system. The dynamic properties depend on the shape of the structure, mass
distribution, stiffness distribution, soil properties, and the type of construction. Non-linear behaviour of the
structural elements should also be taken into account (see 8.1a). A larger value of the seismic design force
should be considered for a structure having less ductility capacity or for a structure where a structural element
failure may lead to complete structural collapse.
d) Importance of the structure in relation to its use
A higher level of reliability is required for buildings where large numbers of people assemble, or structures which
are essential for public well-being during and after the earthquakes, such as hospitals, power stations, fire
stations, broadcasting stations and water supply facilities (see annex A).
NOTE 5 From the point of view of national and political economics, the load factors as related to reliability of the structure

and
(see 8.1) should generally be increased in urban areas with a high damage potential and a high concentration of
E,u E,s
capital investment.
e) Spatial variation of earthquake ground motion
Usually the relative motion between different points of the ground may be disregarded. However, in the case of
long-span or widely spread structures, this action and the effect of a travelling wave which can come with phase
delay should be taken into account.
8 Evaluation of seismic actions by equivalent static analysis
8.1 Equivalent static loadings
In the seismic analysis of structures based on a method using equivalent static loadings, the variable seismic actions
for ULS and for SLS may be evaluated as follows.
a) ULS
The design lateral seismic force of theith level of a structure for ULS,F , may be determined by
E,u,i
n
X
F =
k k k k k F (1)
E,u,i E,u Z E,u D R F,i G,j
j=1
V
or the design lateral seismic shear force for ULS, , may be used instead of the above seismic force:
E,u,i
n
X
V =
k k k k k F (2)
E,u,i E,u Z E,u D R v,i G,j
j=1
where
is the load factor as related to reliability of the structure for ULS (see annex A);
E,u
k is the seismic hazard zoning factor to be specified in the national code or other national documents (see
Z
annex A);
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k is the representative value of earthquake ground motion intensity for ULS to be specified in the national
E,u
code or other national documents by considering the seismicity (see annex A);
k
is the structural factor to be specified for various structural systems according to their ductility, acceptable
D
deformation, restoring force characteristics and overstrength (see annex B);
k is the ordinate of the normalized design response spectrum, as a function of the fundamental natural
R
period of the structure considering the effect of soil conditions (see annex C) and damping property of the
structure (see annex H);
k is the seismic force distribution factor of theith level to distribute the seismic shear force of the base to
F,i
each level, which characterizes the distribution of seismic forces in elevation, where k satisfies the
F,i
P
condition k = 1 (see annex D);
F,i
k is the seismic shear distribution factor of theith level which is the ratio of the seismic shear factor of the
v,i
i
th level to the seismic shear factor of the base, and characterizes the distribution of seismic shear forces
in elevation, wherek = 1 at the base and usually becomes largest at the top (see annex D);
v,i
F is the gravity load at thejth level of the structure;
G,j
n is the number of levels above the base.
b) SLS
The design lateral seismic force of theith level of a structure for SLS,F , may be determined by
E,s,i
n
X
F =
k k k k F (3)
E,s,i E,s Z E,s R F,i G,j
j=1
or the design lateral seismic shear force of theith level for SLS,V , can be used instead of the above seismic
E,s,i
force:
n
X
V =
k k k k F (4)
E,s,i E,s Z E,s R v,i G,j
j=1
where
is the load factor as related to reliability of the structure for SLS (see annex A);
E,s
k is the representative value of earthquake ground motion intensity for SLS to be specified in the national
E,s
code or other national documents by considering the seismicity (see annex A).
k and k may be replaced by a unique representative k , as specified in ISO 2394, in the verification
E,u E,s E
procedure, by which the reliability of the structure and the consequences of failure, including the significance of
the type of failure, are taken into account to specify the load factors
and
(see Table A.2 of annex A).
E,u E,s
The values of the gravity load should be equal to the total permanent load plus a probable variable imposed load
(see annex D). In snowy areas, a probable snow load is also to be considered.
NOTE Depending on the definition of the seismic actions as variable or accidental, the values for the combination of seismic
actions and other actions may be different. For the combination of actions, see ISO 2394.
8.2 Seismic action components and torsion
The two horizontal and vertical components of the earthquake ground motion and their spatial variation, leading to
torsional excitation of structures, should be considered (see annexes E and F).
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The torsional effects of seismic actions should, in general, be taken into account with due regard to the following
quantities: eccentricity between the centres of mass and stiffness; the dynamic magnification caused mainly by the
coupling between translational and torsional vibrations; effects of eccentricities in other stories; inaccuracy of
computed eccentricity; and rotational components of earthquake ground motions.
NOTE 1 The fact that the seismic actions in any direction do not always attain their maxima at the same time should be borne in
mind.
NOTE 2 The vertical component of the earthquake ground motion is usually less intense than the horizontal components and is
characterized by higher frequencies. In the vicinity of the epicentre, however, the vertical peak acceleration can be higher than the
horizontal peak acceleration.
NOTE 3 In a number of structural forms, the magnitude of structural response from torsional vibration can be comparable to or
greater than that from translational vibration. For highly irregular structures, two- or three-dimensional non-linear dynamic
analyses are recommended.
NOTE 4 Corner columns of buildings are subjected to large seismic actions because of the combined effects of torsional
vibrations plus translational vibrations in both directions.
8.3 Seismic actions on parts of structures
When the seismic actions for the parts of the structure are evaluated by the equivalent static analyses, appropriate
factors for seismic forces or shear forces should be used taking into account higher mode effects of the structure
including the parts (see annex D). Larger seismic actions than those given in 8.1 can act on parts of structures such
as cantilever parapets, structures projecting from the roof, ornamentations and appendages. In addition, curtain
walls, infill panels and partitions adjacent to exit ways or facing streets should be designed for safety using the
appropriate values of seismic actions.
In the case of parapets, curtain walls, etc., the seismic actions should be considered to take place in both the normal
and tangent directions to their surface. Vertical forces should also be considered for connections of such
appendages.
9 Evaluation of seismic actions by dynamic analysis
9.1 General
When performing a dynamic analysis, it is important to consider the following items (see annex G).
a) A proper model should be set up, which can represent the dynamic properties of the real structure.
b) Appropriate earthquake ground motions or design response spectra should be chosen, taking into account the
seismicity and local soil conditions.
9.2 Dynamic analysis procedures
The usual dynamic analysis procedures may be classified as
a) the response spectrum analysis for linear or equivalent linear systems, or
b) the time history analysis for linear or non-linear systems.
NOTE The time history analysis is preferable when large amounts of post-elastic deformation can be expected and in the case
of structures such as described in 7.2 a).
9.3 Response spectrum analysis
A site-specific design response spectrum shall be established in the response spectrum analysis. The spectrum
should be based on the proper damping ratio (see annex H). Due consideration should be given to the amount of
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expected post-elastic deformation and associated restoring force characteristics. The design response spectrum
should be smoothed.
In the response spectrum analysis, the maximum dynamic response is usually obtained by the superposition method
of SRSS, taking the predominant vibration modes into consideration (see annex G). Sufficient numbers of modes
should be considered.
Attention should be given to the fact that the SRSS method does not always lead to conservative values, particularly
when frequencies of two or more natural modes are closely spaced. This condition often arises in the vibration of
buildings having large setbacks and in the torsional vibration (see 8.2). For these types of buildings, the CQC method
is recommended (see annex G).
9.4 Earthquake ground motions for time history analysis
Time history analysis may require several earthquake ground motion records to ensure adequate coverage of
expected seismic events. Simulated earthquake ground motions may be used as an alternative. In both cases, the
stochastic nature of earthquake ground motions should be taken into account.
Appropriate earthquake ground motions should be determined for each limit state, taking into account the seismicity,
local soil conditions, return period of historical earthquakes, distance to active faults, errors in the prediction and
design service life of the structure.
a) Recorded earthquake ground motions
When recorded earthquake ground motions are considered in a dynamic analysis, the following records may be
referred to:
— strong earthquake ground motions recorded at or near the site; or
— strong earthquake ground motions recorded at other sites with similar geological, topographic and
seismotectonic characteristics.
Usually these earthquake ground motion records have to be scaled according to the corresponding limit state
and seismicity of the site.
b) Simulated earthquake ground motions
Since it is impossible to predict exactly the earthquake ground motions expected at a site in the future, it may be
appropriate to use simulated earthquake ground motions as design seismic inputs. The parameters of the
simulated earthquake ground motions as well as the number of design inputs should reflect statistically the
geological and seismological data available for the construction site.
NOTE The parameters of the simulated earthquake ground motions are predominant periods, spectral configuration, time
duration (time envelope of the simulated motions), intensity, etc.
9.5 Model of the structure
When setting up a model of the structure, it should represent the dynamic properties of the real structure, such as the
natural periods and modes of vibration, damping properties and restoring force characteristics, taking into account
material ductility and structural ductility. The dynamic properties can be estimated through analytical procedures
and/or experimental results. Consideration should be given to the following:
a) coupling effects of the structure with its foundation and supporting ground;
b) damping in fundamental and higher modes of vibration (see annex H);
c) restoring force characteristics of the structural elements in linear and non-linear ranges including ductility
properties;
d) effects of non-structural elements on the behaviour of the structure;
e) torsional effects in linear and non-linear ranges;
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f) effects of axial deformation of columns and other vertical elements, or overall bending deformation;
g) effects of irregular distribution of lateral stiffness in elevation (e.g. abrupt change of stiffness in particular stories);
h) effects of floor diaphragm stiffness.
When soil structure interaction is considered, it is recommended to establish the model which includes the structure,
foundation, piles and soil.
9.6 Evaluation of analytical results
When dynamic analysis is carried out, the evaluation of seismic actions may be possible solely based on the results
of dynamic analysis. However, the evaluation of seismic actions by equivalent static analysis also gives useful
information.
When the dynamic analysis gives a lower base shear than the equivalent static analysis does, it is recommended that
the design base shear should have some lower limit, e.g. 0,75 to 0,8 of the base shear determined by the equivalent
static analysis.
10 Estimation of paraseismic influences
This standard may be used as an introductory approach for paraseismic influences whose characteristics are similar
to natural earthquakes, e.g. underground explosions, traffic vibration, pile driving and other human activities. Some
advisory remarks are presented in annex J.
©
ISO 2001 – All rights reserved 11

Annex A
(informative)
Load factors as related to the reliability of the structure, seismic hazard
zoning factor and representative values of earthquake ground motion
intensity
A.1 Load factors as related to reliability of the structure,
and
E,u E,s
A.1.1 General
and
are the load factors for ULS and SLS, respectively. They are partial factors for action according to the
E,u E,s
partial factor format in ISO 2394 and can be determined by means of reliability theory. The factors are related to
a) the required degree of reliability,
b) the representative value of the earthquake ground motion intensity,
c) the variability of seismic actions, and
d) the uncertainty associated with idealization of seismic actions and structures, for the corresponding limit state.
A.1.2 Required degree of reliability
The required degree of reliability depends mainly on the importance and/or use of the structure. The importance of
the structure should be determined from the viewpoint of possible consequences of failure during and/or after
earthquakes, e.g. loss of lives, human injuries, potential economic losses and social inconveniences.
For ULS, where design requirements correspond to risk to life during and following severe earthquake ground
motions,
should be determined according to the following categories of structures.
E,u
a) High degree of importance
— structures containing large quantities of hazardous materials whose release to the public may lead to serious
consequences; e.g. storage tanks of chemical materials;
— structures closely related to the safety of lives of the public; e.g. hospitals, fire stations, police stations,
communication centres, emergency control centres, major facilities in water supply systems, electric power
supply systems and gas transmission lines, major roads and railroads;
— structures with high occupancy; e.g. schools, assembly halls, cultural institutions, theatres.
b) Normal degree of importance:
— ordinary structures; e.g. residential houses and apartments, office buildings;
c) Low degree of importance:
— structures with low risk to human lives and injuries; e.g. sheds for cattle or plants, warehouses for non-
hazardous materials.
For SLS, where design requirements correspond to loss of normal use of the structure during and/or after moderate
earthquake ground motions,
should be determined according to the loss of expected use, and the cost and
E,s
disruption due to repair.
©
12 ISO 2001 – All rights reserved

A.1.3 Variability of seismic actions and uncertainty associated with idealisation of seismic
actions and structures
Because of variability of seismic actions,
and
should be determined taking into account the stochastic
E,u E,s
nature of seismic actions. The variability comes from various sources, e.g. seismic activity at the site, propagation
path of seismic waves, local amplification of earthquake ground motion due to soils and structural response. The
uncertainties associated with the idealization of seismic actions and calculation models of the structure should be
taken into account.
A.1.4 Examples of load factors associated with representative values

and
are, as examples, listed in Tables A.1 and A.2 for a region of relatively high seismic hazard, along with
E,u E,s
the representative values of earthquake ground motion intensity k and k (see A.3). Return periods for the
E,u E,s
corresponding representative values are also shown, where the return period is defined as the expected time interval
between which events greater than a certain magnitude are predicted to occur.
An example using the unity load factor for a normal degree of importance is shown in Table A.1, where the return
period for the corresponding limit state is taken into account byk ork . In Table A.2, a common representative
E,u E,s
valuek is used and the degree of importance is taken into account by
or
for the corresponding limit state.
E E,u E,s
Table A.1 — Example 1 for load factors
and
, and representative valuesk andk
E,u E,s E,u E,s
(wherek6=k )
E,u E,s
Return period
Limit state Degree of importance
or
k ork
E,u E,s E,u E,s
fork ork
E,u E,s
a) High 1,5 to 2,0
Ultimate b) Normal 1,0 0,4 500 years
c) Low 0,4to0,8
a) High 1,5 to 3,0
Serviceability b) Normal 1,0 0,08 20 years
c) Low 0,4to0,8
Table A.2 — Example 2 for load factors
and
, and representative valuesk
E,u E,s E
Return period
Limit state Degree of importance
or
k =k =k
E,u E,s E E,u E,s
fork
E
a) High 3,0 to 4,0
Ultimate b) Normal 2,0
c) Low 0,8to1,6
0,2 100 years
a) High 0,6 to 1,2
Serviceability b) Normal 0,4
c) Low 0,16 to 0,32
A.2 Seismic hazard zoning factor,k
Z
The seismic hazard zoning factor,k , reflects the relative seismic hazard of the region. This factor is evaluated taking
Z
into account historical earthquake data, active fault data and other seismotectonic data in and around the
construction site. Usually at the region of the highest seismic hazard, the factor is unity and the factor decreases
according to the seismic hazard of the respective region. A zoning factor larger than unity can be used when the
seismic hazard of the region is extremely high. A contour map for the representative value of earthquake
...