ISO 10721-1:1997

Steel structures — Part 1: Materials and design

Establishes the principles and general rules for the use of steel materials and design of steel structures in buildings. It is also applicable to bridges, civil engineering and related structures, but for such structures it may be necessary to consider other requirements.

Structures en acier — Partie 1: Matériaux et conception

General Information

• Status: Published
• Publication Date: 19-Feb-1997
• ICS: 91.080.10 - Metal structures
• ICS: 91.080.13 - Steel structures
• Technical Committee: ISO/TC 167/SC 1 - Steel: Material and design
• Drafting Committee: ISO/TC 167/SC 1 - Steel: Material and design
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 11-Jul-2025
• Completion Date: 13-Dec-2025

Standards Content (Sample)

INTERNATIONAL IS0
STANDARD 10721-I
First edition
1997-02-01
Steel structures -
Part 1:
Materials and design
Structures en acier -
Partie 1: Matgriaux et conception
Reference number
IS0 10721-1:1997(E)
ISOlO721-1:1997(E)
Page
CONTENTS
1 SCOPE .
.......................................................... 1
2 NORMATIVE REFERENCES
..................................................... 2
3 DEFINITIONS AND SYMBOLS
3.1 Definitions .
3.2 List of svmbols . 5
4 DOCUMENTATION OF THE DESIGN . 11
................................................................................. 11
4.1 Calculations
......................................................................................... 11
4.2 Testing
............................................................................ 11
4.3 Documentation
....................................................... 11
5 BASIC DESIGN PRINCIPLES
............................... 11
5.1 Obiectives and general recommendations
5.2 Limit states .
............................... 12
5.3 Design situations and member resistance
5.3.1 General .
5.3.2 Design situations . 12
5.3.3 Member resistance . 13
...................................................................... 13
6 BASIC VARIABLES
61 General .
6:2 Actions .
6.2.1 General . 13
6.2.2 . 14
Design value
...................................................................................... 14
6.3 Materials
6.3.1 General .
6.3.2 Structural steels .
6.3.3 Connecting devices .
6.3.4 . 15
Testing and inspection of materials
............................................................. 15
64 Geometrical parameters
......................................................... 15
6:5 Desiqn value of resistance
0 IS0 1997
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ii
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ANALYSIS OF STRUCTURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-
General .
7.1
Structural behaviour .
7.2
Methods of analysis .
7.3
General .
7.3.1
Elastic analysis .
7.3.2
Elastic-plastic analysis .
7.3.3
............................................................................
7.3.4 Plastic analysis
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8 ULTIMATE LIMIT STATES
. . . . .*.*.* 17
8.1 Member desion
8.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1.2 Cross-sectional resistance
. . . . . . . . . . . . . . . . .‘. 17
8.1.3 Member stability
8.2 Resistance of members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.1 Member strength . . . . . . . . . . . . . . . . . . . . . .~.~.~.
Classification of cross sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.3
General .‘.,. 18
8.3.1
Definitions of classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~. 18
8.3.2
Maximum width-thickness ratios of elements subjected to
8.3.3
compression and/or bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 19
8.4 Flexural buckling
............................................................ 19
8.4.1 Effective buckling length
................................................................................. 19
8.4.2 Slenderness
............................................................. 20
8.4.3 Compression resistance
.................................................................... 20
8.4.4 Buckling strength f,
....................... 20
8.4.5 Compression members subjected to moments
Buckling of built-up members . 21
8.4.6
Torsional and lateral torsional bucklinq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
85 .
Torsional buckling . 21
8.5.1
Lateral torsional buckling . 21
8.5.2
Buckling strength< f,, and fcL . 21
8.5.3
..................................... 22
8.5.4 Bracing of beams, girders and trusses
8.6 Buckling of plates . . . . . . . . .‘. 22
General . .‘.,. 22
8.6.1
Uniaxial force or in-plane moment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.6.2
Shear resistance of webs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~. 23
8.6.3
Combined forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.6.4
. . . . . . . . . . . . . . .a.
8.6.5 Webs or panels subdivided by stiffeners 23

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8.7
Connections, general requirements
. . . . . . .‘.
88 .
Bolted connections . . . . . . . . . . . . . . . . . . .~.~.
8.8.1
General .
8.8.2
Bolting details .
8.8.3
Strength of connections with bolts and rivets
.........................
8.8.4
Slip coefficients .
8.8.5
Deduction for holes
....................................................................
8.8.6
Length of connection
....................................................................
,.,.*.,.,.
Welded connections
8.9
Scope .
8.9.1
.................................................................
8.9.2 General requirements
............................................................................
8.9.3 Types of welds
...................................................................
8.9.4 Design assumptions
.......................................................................
8.9.5 Design provisions
8.9.6 Complete joint penetration groove welds in butt
...............................................................................
and tee joints
...................................................................................
8.9.7 Fillet welds
.....................................................................
8.9.8 Plug and slot welds
. . . . . . . . . . . . . .~.‘
8.10 Joints in contact bearing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 SERVICEABILITY LIMIT STATES
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 FATIGUE
10.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
10.1 .I General .
...................................................................................
10.1.2 Limitations
........... 35
10.1.3 Situations in which no fatigue assessment is required
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fatigue assessment procedures
10.2
............... 36
10.2.1 Fatigue assessment based on nominal stress range
........ 37
10.2.2 Fatigue assessment based on a geometric stress range
............................................................................
10.3 Fatioue loading
.................................................................
10.4 Fatigue stress spectra
........................................................................
10.4.1 Stress calculation
...................................................
10.4.2 Design stress range spectrum
.~.,.~.,.
10.5 Fatigue strength
10.5.1 Definition of fatigue strength curves for classified structural
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
details
10.5.2 Definition of reference fatigue strength curves for
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
non-classified details
.~.,.,.,.
10.6 Fatioue strength modifications
Partial safety factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .‘.
10.7
IV
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...................................
10.7.1 Partial safety factors for fatigue loading
.................................
10.7.2 Partial safety factors for fatigue strength
............................................
10.7.3 Values of the partial safety factors
.............................................................................................................
Annex A
BASIC VARIABLES .
A.6
.......................................................................................
A.6.3 Materials
A.6.3.2 Structural steel .
...................................................... 41
A7 . ANALYSIS OF STRUCTURES
A.7.1 General .
A.7.2 Structural behaviour .
A.7.3 Methods of analysis .
A.7.3.2 Elastic analysis .
Plastic analysis .
A.7.3.4
ULTIMATE LIMIT STATE .
A.8
Resistance of structural members .
A.8.2
Classification of cross sections .
A.8.3
..........................................................................................
A.8.3.1 General
...................................................................
A.8.3.2 Definitions of classes
Maximum width-thickness ratios of elements subjected to
A.8.3.3
...................................................... 46
compression and/or bending
............................................................................ 48
A.8.4 Flexural buckling
Effective length .
A.8.4.1
Slenderness .
A.8.4.2
Compression resistance .
A.8.4.3
Determination off, .
A.8.4.4
Compression members subjected to moments .
A.8.4.5
Buckling of built-up members .
A.8.4.6
Torsional and lateral torsional bucklinq .
A.8.5
........................................................ 57
A.8.5.3 Buckling strengths f,, and f,,
...................................... 60
A.8.5.4 Bracing of beams, girders and trusses
A.8.6 Bucklino of plates .
General .
A.8.6.1
............ 61
Plates subjected to uniaxial force or in-plane moment
A.8.6.2
Shear resistance of webs .
A.8.6.3
.............................................................. 67
A.8.6.4 A combination of forces
.................................. 70
A.8.6.5 Webs or panels subdivided by stiffeners

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..................................................................... 73
A.8.8 Bolted connections
A.8.8.2 Bolting details .
......................... 74
A.8.8.3 Strength of connections with bolts and rivets
A.8.8.4 Slip coefficients .
.................................................................. 77
A.8.8.6 Length of connection
................................................................... 77
A.8.9 Welded connections
................................................................. 77
A.8.9.2 General requirements
................................................................... 77
A.8.9.4 Design assumptions
....................................................................... 77
A.8.9.5 Design provisions
.......................................... 78
A.8.9.6 Groove welds in butt and tee joints
A.8.9.7 Fillet welds .
A.10 FATIGUE .
A.10.1 Scope .
...........
A.10.1.3 Situations in which no fatigue assessment is required 79
A.10.2 Fatigue assessment procedures . 80
Fatigue assessment based on nominal stress range . 80
A.10.2.1
........ 80
A.10.2.2 Fatigue assessment based on a geometric stress range
............................................................................ 80
A.10.3 Fatigue loading
................................................................. 81
A.10.4 Fatigue stress spectra
Design stress range spectrum . 81
A.10.4.2
.......................................................................... 81
A.lO.5 Fatigue strength
A.10.5.1 Definition of fatigue strength curves for classified
................................................................. 84
constructional details
A.10.5.2 Definition of reference fatigue strength curves for
non-classified details .
A.10.6 Fatigue strength modifications . 105
A.10.6.1 Influence of mean stress level in non-welded or stress
relieved welded details . 105
............................................................... 105
A.10.6.2 Influence of thickness
................................................................. 105
A.10.7 Partial safety factors
A.10.7.3 Values of partial factors . 105
Annex B (Reference publications) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
VI
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Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 10721-I was prepared by Technical Committee ISOmC 167, Steel and aluminium
structures, Subcommittee SC 1, Steel: Material and design.
IS0 10721 consists of the following parts under the general title Steel and a/minim structures:
Part 1: Materials and design
Part 2: Fabrication and erection
Annexes A and B of this part of IS0 10721 are for information only.
vii
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IS0 10721=1:1997(E)
Introduction
This part of IS0 10721 establishes a common basis for drafting national standards for the use of materials in steel
structures and for their design, in order to ensure adequate and consistent measures regarding safety and
serviceability.
Annex A of this part of IS0 10721 contains noncompulsory recommendations which may be used as guidelines for
practical design.
The specific and numerical requirements for the completion of structures which are optimal with respect to the
state of a country’s economy, development and general values should be given in the national codes of the
country.
The design rules given concern limit-state verifications for comparing the effects of actions or combinations of
actions with the strength (resistance) of the structure and its components.
. . .
VIII
IS0 10721=1:1997(E)
INTERNATIONAL STANDARD o IS0
Steel structures -
Part 1:
Materials and design
1 Scope
This part of IS0 10721 establishes the principles and general rules for the use of steel materials and design of steel
structures in buildings.
NOTE 1 The degree of reliability should be as specified in national codes. In the establishment of design safety factors,
due consideration should also be given to IS0 10721-2 for fabrication of steel structures.
This part of IS0 10721 is also applicable to bridges, off-shore and other civil engineering and related structures, but
for such structures it may be necessary to consider other requirements.
This part of IS0 10721 does not cover the special requirements for steel structures in corrosive environments
beyond normal atmospheric conditions and corrosion protection with regard to fatigue design.
This part of IS0 10721 does not cover the special requirements of seismic design.
For welded connections and for structures subject to fatigue, special considerations regarding the scope of this
document are presented in 8.9 and 10.1 respectively.
NOTE 2 Rules and recommendations regarding composite steel and concrete structures and fire safety of steel structures
will subsequently be issued as separate International Standards.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
IS0 10721. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of IS0 10721 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently
valid International Standards.
IS0 630: 1995, Sfructural steel - Plates, wide f/a ts, bars, sections and profiles.
IS0 898: 1988-l 994, Mechanical properties of fasteners (all parts).
IS0 2394: -‘), General principles on reliability of structures.
IS0 3989: -*I,
Bases for design of structures - Notations - General symbols.
- Ends of parts with external metric IS0 thread.
IS0 4753: 1983, Fasteners
IS0 4951:1979, High yield strength steel bars and sections
IS0 6892: _3’, Metallic materials - Tensile testing at ambient tempera We.
1) To be published. (Revision of IS0 2394:1986)
2) To be published. (Revision of IS0 3898:1987)
3) To be published. (Revision of IS0 6892:1984, replacing IS0 82:1974)
0 IS0
IS0 10721-1:1997(E)
3 DEFINITIONS AND SYMBOLS
For the purposes of this part of IS0 10721, the following definitions and symbols apply.
. Definitions
The states beyond which the structure no longer satisfies the
Limit states:
design req uirements.
The limit states corresponding to the maximum load carrying
Ultimate limit state:
resistance (safety related).
Serviceability limit The limit states related to normal use (often related to function).
state:
The time the structure is to be used under the given design
Specified life:
assumptions.
concentrated or distributed forces acting
Direct action: One or a set of on the
as selfweight wind,
structure, such -I imposed specified actions,
etc.
The cause of imp0 sed or constrained d eformations in the
Indirect action:
structure, such as temperature effects, settlements creep etc.
I
The numerical value of an action #either defined by the authorities
Nominal action:
or by the contract documents. When this value corresponds to a
specified probability to be exceeded within a specified reference
time, it is called characteristic action, and it is calculated in
accordance with IS0 2394.
Actions used in calculations. The design action is the nominal
Design action:
action multiplied by its partial safety factor yf, or it is the
combination of nominal actions, each multiplied by its partial
safety factor yf for the relevant limit state.

IS0 107214:1997(E)
0 IS0
Shake down: The process of local yielding due to the initial applications of
variable actions, leading to a condition of residual stress where
all further applications can be sustained elastically (applies
particularly to the formation of plastic hinges).
Action which is unlikely to act throughout a given design situa-
Variable action:
tion or for which the variation in magnitude with time is not -
monotonic nor negligible in relation to the mean value.
Repetetive action: Design action which involves stress fluctuations leading to
possible fatigue effects, i.e. it is the design action to be used for
checking the fatique limit state.
Characteristic
material property:
The value of material prop
Desig n material erties obta ined dividing the
bY
rty: . characteristic property by a partial m ateri al s afety factor.
ProPe
V
Nominal strength The strength or resistance alue based o n specified
or resistance: characteristic material and eometric pro efties.
9 P
Design strength The nominal strength or resistance divided by the
or resistance: appropriate partial safety factor for resistance,
Yr*
Normal use is that which conforms to the loading and
Normal use:
performance intended by the designer, or as specified in
codes of practice, or by other relevant requirements.
Damage, by gradual crack propagation in a stuctural part, caused
Fatigue:
by repeated stress fluctuations.
Fatigue loading: A set of typical load events described by the position of loads,
their intensities and their relative occurence.
Loading event: A defined loading sequence applied to the structure and giving
.rise to a stress history variation.
Equivalent A sim plified fatigue loading representing the fatigue effects of all
lo adin gs events.
fatigue loading:
Stress history: A record or a calculation of the stress variation at a particular
point of a structure during the load event.
The algebraic difference between two extrema of the stress
Stress range:
history (ACTS = o,,,~ - Omin or 111 = T,, - T,i”). This difference
is usually identified by. a stress cycle counting method.
Nominal stress: A fatigue design stress in the parent material adjacent to
potential crack location calculated in accordance to simple elastic
strength of materials theory. For the purpose of fatigue
assessment of a particular class of constructional detail, the
design stress is either the normal stress (axial and bending
stress) or/and the shear stress. Where there is a geometric
discontinuity, not taken into account in the classi-
fication of the constructional detail, the nominal stress shall be
modified by the use of stress concentration factors.

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IS0 10721-1:1997(E)
Geometric stress: A fatigue design stress, adjacent to the weld toe, defined as the
extrapolation of the maximum principal stresses. The geometric
stress takes into account the overall geometry of the
constructional detail, excluding local stress concentration effects
due to weld geometry and inherent defects in weld and adjacent
parent metal. (The geometric stress is often referred in the
litterature as the “hot spot stress”).
A particular method used for counting the number of stress
Cycle counting:
cycles and related stress ranges from a stress history.
Histogram of the frequency of occurrence for all stress ranges
Stress-range
of different magnitudes recorded or calculated for a particular
spectrum:
loading event.
Design spectrum: The total of all stress spectra relevant to the fatigue assess-
ment.
lent stress The constant-amplitude stress range that would result in the
Equiva
same fatigue life (number of cycles of stress ranges) as for the
range:
spectrum of variable amplitude stress ranges based on a Miner’s
summation.
Miner’s summation: A cumulative linear damage calculation based on the
Palmgren-Miner rule.
Constant amplitude The limiting stress range value above which a fatigue
fatigue limit: assessment is necessary.
Detail category: The designation given to a particular welded or bolted detail, in
order to indicate which fatigue strength curve is applicable for
the fatigue assessment.
The quantitative relationship between stress range and
Fatigue strength
number of stress cycles to fatigue failure (selected on the basis
curve:
of a statistical analysis of available test data of a constructional
detail).
The reference period of time for which a structure is required to
Design life:
perform safely with an acceptable probability that failure by
fatigue or cracking will not occur.
Cut-off limit: Limit below .which stress ranges of the design spectrum do not
contribute to fatigue dam age.
Groove (butt) weld: A .weld made in a preparation to receive weld metal. (Also
referred to as a butt weld).
0 IS0 IS0 10721-1:1997(E)
Fig. 3.1 Fatigue strength curve definitions
32 . List of symbols
(see also IS0 3898)
LATIN UPPER CASE LETTERS:
A
Cross-sectional area
Effective cross-section area
A,
Gross section area
A*
Cross-sectional area of longitudinal stiffener
AL
Effective area of longitudinal stiffener
4,
For fillet welds, A,,, =
effective size multiplied by its length.
For butt joints, A, = thickness of base metal multiplied by its length. For
T-joints, A, =
size of fusion face in base metal multiplied by the length of
the weld
Net section area
A”
Cross-sectional area of a stiffener
As
Nominal area of the threaded part of a bolt
ASP
Cross-sectional area of transverse stiffener
Effective shear area of bolts
A,
Cross-sectional area of web
A,
Effective area of weld (effective throat of weld multiplied by its length).
hfv
For plug or slot welds, A,,,, = area of faying surface

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IS0 10721=1:1997(E)
Coefficient
B
Warping constant of torsion for the cross-section
C
W
E Modulus of elasticity (Young’s modulus)
E Tangent modulus
T
F Force, action
Bearing resistance of bolts
FtJ
Characteristic action
h
Design force, action
F,
Preloading force in bolts
- FP
Slip resistance of bolts
F*
Tensile force resistance of bolts
Ft.
Shear force resistance of bolts
Fv
Modulus of shear = El (211 +u))
G
Moment of inertia (about y- and z-axis, respectively)
It I,, I,
Moment of inertia of a stiffener
Is
I Polar moment of inertia
P
St. Venant torsion constant of the cross-section
L
Coefficient for buckling length
KE
l L Length
Effective length (in buckling
L
E
Laterally unsupported lengtl
Lo
L Load distribution length
s
Bending moment (about y- and z-axis, respectively)
Mt M,, M,
Moment resistance (about y and z-axis, respectively)
Mrdr Mdy1 M,,
Reduced moment resistance
Mdr
M Elastic lateral torsional buckling moment
EL
Plastic moment of flanges
Mf
Moment resistance in lateral torsional
MLd
buckling
Plastic moment = f,W,
MP
IS0 10721=1:1997(E)
0 IS0
Torsional moment
MT
Plastic moment of web
MW
Yield moment = f,W
MY
The larger and the smaller moments at the supported ends of a member
Ml, M2
N Normal force (chapt. 8)
N Number of fatigue strength cycles (chapt 10)
N Buckling resistance (chapt. 8)
cd
Number of cycles (2*106) at which the reference value of the fatigue
NC
strength curve is defined (chapt. 10)
Buckling resistance about y- and z- axis, respectively
Ncyf NC,
Number of cycles for which the constant amplitude fatigue limit is defined
ND
(= 5.107
Normal force resistance
Normal force design resistance
N,d
n2 El
Elastic buckling force of a pinned column =
NE, NED, NEz
(about the y- and z-axis, respectively).
I? El
N Elastic buckling load of a structure = 1
Ecr
Lk
Elastic torsional buckling load
NET
Number of cycles of stress ADi to cause failure
Ni
Number of cycles for which the cut-off limit is defined (= 1 O*)
. -NL
Plastic normal force resistance
NP
N Torsional buckling resistance
Td
N Ultimate tensile yield force resistance
yd
Ultimate tensile strength
Nvd
P Concentrated force
Concentrated force resistance
‘d
R Resistance
S Static moment of area
T Tensile force (in a bolt)
V Shear force
V Shear resistance
cd
0 IS0
IS010721=1:1997(E)
Notional shear force in built up members
‘i
Elastic section modulus
WI w,, w,
Elastic section modulus of the effective cross section
WI w,, w,,
Plastic section modulus
wpt Wpy’ Wpz
LATIN LOWER CASE LETTERS:
Distance. The weld throat “a-dimension”
a, a,, a2
b Width (of plates)
Effective width
be, be, 1 be2
C Distance
Coefficients for stiffeners
CL, ct
Diameter. Depth
d
d Effective depth
e
Distance (for bolts)
Eccentricity.
e, ey, e,
Bearing strength in bolted connections
f tl
Buckling strength (about y- and z-axis, respectively)
L fcyr f,,
f
f c lv I
cd
f Lateral torsional buckling strength
CL
Torsional buckling strength
- fcT
Design strength
fd
f Local elastic plate buckling strength
CP
Specified ultimate tensile strength of base material or bolt material
f ”
Specified ultimate tensile strength of weld material
fuw
Specified yield strength of material or the stress giving 0.2 % permanent
fY
strain
f Reduced (effective) yield strength of material
Ye
Specified yield strength of weld material
fw
Distance between bolt holes (the gauge)
h Height (of web)
Effective heigth
he
i, i,, i, Radius of gyration (about y- and z-axis, respectively)
0 IS0 IS010721=1:1997(E)
Polar radius of gyration
Coefficient for th e effect of the stress distribution and the support
k, k,
conditions on ela stic plate buck1 ing
Compression member buckling coefficients
Elastic shear buckling coefficient
Length, span
Slope constant of the fatigue strength curve. The curves have slopes of
-l/3 and /or -l/5 and the corresponding values of the slope constant m
are 3 and 5
Number. Coefficient (for built-up-members)
n
Equivalent number of stress cycles
Number of applied stress cycles AOi
ni
r Radius
S Distance between bolt holes (the staggered pitch). Weld size for T-welds
t Thickness
Flange thickness
If
Web thickness
Ll
Cartesian Coordinates (x along member axis)
Xl YI z
Shear center coordinates
Ys, zs
GREEK LETTERS:
Angle. Buckling curve designation. Coefficient for arbitary eccentricity of
Q
column load. Bearing stress coefficient for bolted connections. Aspect
ratio for plates
Reduction coefficient for the length
Coefficient for arbitrary eccentricity.
P
of bolted connections
Equivalent uniform moment coefficient for beam-columns
P? Pyr 4
Partial coefficient
Y
Partial safety factor for actions
Yf
Partial safety factor for resistance (in this document identified as
Y*
resistance factor)
Resistance factor for a connection
Y
fC
Slip resistance factor
Y
rs
0 IS0
IS0 10721=1:1997(E)
normal stress
AD Nominal stress range
shear stress)
Nominal stress range
AT
Reference value of the fatigue strength at 2 million cycles (normal stress)
A%
Stress range corresponding to the constant amplitude fatigue limit, simply
na,
called the “fatigue limit”
Equivalent stress range of constant .amplitude cycles (normal stress)
na,
Stress range corresponding to the cut-off limit
Au,
Fatigue strength (normal stress)
AoF3
AT, Reference value of the fatigue strength at 2 million cycles (shear stress)
Fatigue strength (shear stress)
A%
Initial out-of straightness
4nf 6,
Strain
Coefficient. Coordinate
/I
Coefficient
k,! kl
A Slenderness
A Slenderness parameter = ndE/f,
C
2 Relative slenderness of columns
Relative slenderness limit, below which strain hardening effects in
A0
columns occur
Effective relative slenderness for members with L-sections
A, .
Relative slenderness of plate
AP
-
A Effective relative slenderness for built-up members
i
Slip coefficient
P
Coefficients (flexural buckling)
Py, 4
Coefficient (lateral torsional buckling)
PL
Lateral torsional buckling coefficient
Cross sectional parameter
Coefficient (bending moment diagram)
IS0 10721=1:1997(E)
0 IS0
4 DOCUMENTATION OF THE DESIGN
4.1 Calculations
Design calculations shall include
- design assumptions (calculation model),
- action arrangements (including imposed actions),
- material properties,
- properties of connecting devices and
- verification of the relevant limit states.
4.2 Testing
4.2.1 The design may be verified by testing, or by testing combined with calculations,
4.2.2 The magnitude and distribution of actions during tests shall correspond to the &sign
actions for the relevant limit states.
Sample size, scale effects and other relevant effects shall be considered in establishing
4.2.3
the design strength of the structure or structural element.
. 4.3 Documentation
The calculations, drawings, or other relevant documents shall be presented in a manner
which is appropriate to the information and documentation requirements
5 E3kikC DESIGN PRINCIPLES
51 . Objectives and general recommendations
Structures or structural elements shall be designed and maintained such that they, with
an appropriate degree of reliability,
- will sustain actions likely to occur
- will perform adequately in normal use
- have a sufficient durability.
.
These requirements, which can be satisfied by use of this code, shall apply throughout
the specified life of a structure, including the period of construction.
The degree of reliability should be chosen to account for the possible consequences of
exceeding the design criteria of the limit states. These consequences will vary. The
following classification is appropriate:
- risk to life is negligible and economic consequences are small or negligible
- risk to life exists and/or economic consequences are considerable
- risk to life is high and/or economic consequences are great.
The choice of structural concept should also take into account accidental events and
their possible consequences. The main structure should as far as practical not be
damaged to an extent which is disproportionate to the accidental event.
0 IS0
IS0 10721=1:1997(E)
The design of steel structures should aim at a ductile behaviour, avoiding brittle fracture
by appropriate choice of materials, material thickness, connections and selection of
details and fabrication methods. See also 6.3.2.3.
Limit states
52 .
The structural performance of a whole structure or parts of it shall be described with
reference to limit states.
The limit states. are classified into the following two categori es, which may also be
subclassi fied:
The ultimate limit states.
a)
b) The serviceability limit states.
Ultimate Limit States correspond to:
- overturning of the structure, or parts of the structure;
due to exceedance of the material
rupture of critical sections of the structure
strength;
- transformation of the structure into a mechanism (collapse);
loss of stability (buckling, etc.);
- excessive displacements or deformations, leading to a change of geometry, which
necessitates replacing the structure;
- failure of a structure or a member subjected to repetitive actions (fatigue).
The Serviceability Limit States correspond to:
- deformations which affect the normal use or performance of structural or
non-structural elements;
- oscillations producing discomfort or affecting structural or non-structural elements
or equipment;
- local damage, including limited cracking, which reduces the durability of a
structure or affects the performance of structural or non- structural elements.
. Design situations and member resistance
5.3.1 General
---w-m-
All relevant limit states shall be considered in design. A calculation model shall be
established for each specific limit state.
Design situations
5.3.2
--m---e----------
For any structure it is generally necessary to consider
several design situations. Corresponding to each of these, there may be different
structural systems, different reliability requirements, different design values, and different
environmental conditions. The design situations may include permanent, transient and
accidental conditions.
0 IS0 IS010721=1:1997(E)
5.3.3 Member resistance
---__------__---_-_-------_-
be designed for s
5.3.3.1 For the ultimate limit states, the structure shall ufficient resistance, i.e.
strength and/or stability. At every part of the s tructure the mem ber resistance shall be
larger than or equal to the action effects o If the relevant ultimate limit load cases.
5.3.3.2 Variable and repetitive actions shall be considered. At-every part of the structure the
fatigue strength shall be larger than or equal to the effects of the repetetive actions, .
5.3.3.3 For the serviceability limit states the structure shall be designed to eliminate unacceptable
levels of vibration, deflections or slip under the effects of the relevant serviceability
actions.
6 BASIC VARIABLES
61 . General
The design assumptions shall include the necessary set of basic variables. The normal
basic variables are the relevant parameters characterizing:
actions;
material properties;
structural geometry;
environmental conditions.
Other
variables shall also be considered, such as uncertainties of calculation models.
62 . Actions
6.2.1
Actions are characterized as
1. Direct actions:
One or an assembly of concentrated or distributed forces acting on the structure,
such as selfw.eight, imposed specified actions, wind etc.
2. Indirect actions:
The result of imposed or constrained deformations in the structure, such as
temperature effects, settlements, creep etc.
For characteristic values of the actions, reference is made to the relevant IS0 standard or
to the appropriate national standards.
According to their occurrence in time and to the variation of their magnitude with time,
actions are classified as follows:
permanent actions,
variable actions,
repetitive actions,
accidental actions,
temporary or transient actions.
A load case comprises a relevant combination of actions.
0 IS0
IS0 10721-I :I 997(E)
According to the way in which the structure responds to an action, one may distinguish
between
- static actions, which are acting on the structure without causing any significant
oscillations of the structure or parts of the structure.
- dynamic actions, which may cause impact effects or significant oscillations of the
structure or parts of the structure.
- repetitive actions, which may cause fatigue.
Dynamic actions, which cause impact effects, may be handled as static by an appropriate
increase of the magnitude of its corresponding static effect, except for the cases when
such dynamic effects are cyclical or repetitive.
Design value
6.2.2
For a specific limit state the design value, F,, is the representative action or
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