ISO 14347:2008
(Main)Fatigue — Design procedure for welded hollow-section joints — Recommendations
Fatigue — Design procedure for welded hollow-section joints — Recommendations
ISO 14347:2008 gives recommendations for the design and analysis of unstiffened, welded, nodal joints in braced structures composed of hollow sections of circular or square shape (with or without rectangular chord) under fatigue loading. ISO 14347:2008 applies to structures: fulfilling quality requirements for hollow sections; complying with recommended weld details; employing permitted steel grades; having hollow section joints; having either square or rectangular hollow sections with a thickness between 4 mm and 16 mm, or circular hollow sections with a thickness between 4 mm and 50 mm; having as stress range the range of “hot-spot” stress; having identical brace (branch) members. ISO 14347:2008 applies to both hot-finished and cold-formed steel structural hollow sections, complying with the applicable national manufacturing specification, that fulfil specified quality requirements. ISO 14347:2008 applies to joints consisting of circular hollow sections (CHS) or rectangular hollow sections (RHS) as used in uniplanar or multiplanar trusses or girders, such as T-, Y-, X-, K-, XX-, and KK-joints.
Fatigue — Procédure de dimensionnement à la fatigue des assemblages soudés de profils creux — Recommandations
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 14347
First edition
2008-12-01
Fatigue — Design procedure for welded
hollow-section joints —
Recommendations
Fatigue — Procédure de dimensionnement à la fatigue des
assemblages soudés de profils creux — Recommandations
Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved
Contents Page
Foreword .iv
1 Scope.1
1.1 General .1
1.2 Materials .1
1.3 Types of joints .1
2 Normative references.1
3 Terms and definitions .2
4 Symbols and abbreviated terms .7
5 Cumulative fatigue damage.12
6 Partial safety factor .12
7 Fatigue design procedures.12
7.1 Hot-spot stress method .12
7.2 Design procedures .13
8 Fatigue strength .13
8.1 Member forces .13
8.2 Nominal stress ranges.14
8.3 SCF calculations.14
8.4 Hot-spot stress ranges .14
8.5 Fatigue strength curves.15
9 SCF calculations for CHS joints .17
9.1 Uniplanar CHS T- and Y-joints .17
9.2 Uniplanar CHS X-joints .18
9.3 Uniplanar CHS K-joints with gap .18
9.4 Multiplanar CHS XX-joints .19
9.5 Multiplanar CHS KK-joints with gap.20
9.6 Minimum SCF values .21
10 SCF calculations for RHS joints .21
10.1 Uniplanar RHS T- and X-joints .21
10.2 Uniplanar RHS K-joints with gap .22
10.3 Uniplanar RHS K-joints with overlap.23
10.4 Multiplanar RHS KK-joints with gap.24
10.5 Minimum SCF values .25
Annex A (normative) Quality requirements for hollow sections.26
Annex B (normative) Weld details.27
Annex C (informative) A fatigue assessment procedure .29
Annex D (normative) SCF equations and graphs for CHS joints.31
Annex E (normative) SCF equations and graphs for RHS joints .47
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
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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 14347 was prepared by the International Institute of Welding, Commission XV, Design, analysis and
fabrication of welded structures, recognized as an international standardizing body in the field of welding in
accordance with Council Resolution 42/1999.
Requests for official interpretations of any aspect of this International Standard should be directed to the ISO
Central Secretariat, who will forward them to the IIW Secretariat for an official response.
iv © ISO 2008 – All rights reserved
INTERNATIONAL STANDARD ISO 14347:2008(E)
Fatigue — Design procedure for welded hollow-section joints —
Recommendations
1 Scope
1.1 General
This International Standard gives recommendations for the design and analysis of unstiffened, welded, nodal
joints in braced structures composed of hollow sections of circular or square shape (with or without
rectangular chord) under fatigue loading.
This International Standard applies to structures:
a) fulfilling quality requirements for hollow sections (see Annex A);
b) complying with recommended weld details (see Annex B);
c) employing permitted steel grades (see 1.2);
d) having hollow section joints (see 1.3);
e) having either
1) square or rectangular hollow sections with a thickness between 4 mm and 16 mm, or
2) circular hollow sections with a thickness between 4 mm and 50 mm;
f) having as stress range the range of “hot-spot” stress;
g) having identical brace (branch) members.
1.2 Materials
This International Standard applies to both hot-finished and cold-formed steel structural hollow sections,
complying with the applicable national manufacturing specification, that fulfil specified quality requirements
(see Annex A).
1.3 Types of joints
This International Standard applies to joints consisting of circular hollow sections (CHS) or rectangular hollow
sections (RHS) as used in uniplanar or multiplanar trusses or girders, such as T-, Y-, X-, K-, XX-, and
KK-joints (see Figure 1 and Figure 2).
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 630:1995, Structural steels — Plates, wide flats, bars, sections and profiles
a) CHS T-joints b) CHS Y-joints c) CHS X-joints d) CHS K-joints
with gap
e) RHS T-joints f) RHS X-joints g) RHS K-joints h) RHS K-joints
with gap with overlap
NOTE RHS are assumed to be square, although this International Standard is likely to be applicable to rectangular
chord members, welded to square branch members.
Figure 1 — Types of uniplanar joints covered by this International Standard
a) CHS XX-joints b) CHS KK-joints with gap c) RHS KK-joints with gap
NOTE RHS are assumed to be square, although this International Standard is likely to be applicable to rectangular
chord members, welded to square branch members.
Figure 2 — Types of multiplanar joints covered by this International Standard
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
brace
branch
〈welded hollow section joints〉 cut and welded member
See Figure 3.
2 © ISO 2008 – All rights reserved
Key
1 load applied in the branch
2 crown point
3 branch
4 saddle point
5 weld
6 chord
a) Joint nomenclature
Key
1 chord wall
2 stress increase due to weld geometry
3 brace hot-spot stress
4 weld toe
5 extrapolation of geometric stress distribution to weld toe
6 stress in branch
7 nominal stress
8 increase in stress due to overall joint geometry
9 branch wall
10 weld
b) Stress distribution in branch
Figure 3 — Hot-spot stress definition in nodal joints
Key
1 chord wall
2 stress increase due to weld geometry
3 chord hot-spot stress
4 weld toe
5 extrapolation of geometric stress distribution to weld toe
6 stress in chord
7 nominal stress
8 increase in stress due to overall joint geometry
9 branch wall
c) Stress distribution in chord
Figure 3 (continued)
3.2
constant amplitude fatigue limit
〈welded hollow section joints〉 stress range for a specific ∆S-N curve when the number of cycles, N, is 5 million
or greater
3.3
cut-off limit
stress range for a specific ∆S-N curve when the number of cycles, N, is 100 million or greater, used in the
assessment of fatigue under variable amplitude loading
3.4
fatigue
deterioration of a component due to the initiation and growth of cracks under fluctuating loads
3.5
fatigue life
endurance
N
f
number of applied cycles to achieve a defined failure criterion
[ISO 1099:2006, 3.14]
NOTE In this International Standard, crack growth through the wall thickness is considered as failure.
3.6
gap length
g
distance measured along the length of the connecting face of the chord between the toes of the adjacent
brace members
See Figure 4.
4 © ISO 2008 – All rights reserved
Key
1 member (overlapping in the lower diagram)
2 optionally overlapped member
NOTE For variable definitions, see Clause 4.
Figure 4 — Definition of gap g and overlap q
3.7
hot-spot stress
〈welded hollow section joints〉 point along the weld vicinity where the extrapolated primary stress has its
maximum value (i.e. the maximum geometric stress)
NOTE This definition differs from the more general definition of hot-spot stress as the structural stress at the weld toe.
The extrapolation is carried out from the region outside the influence of the eff
...
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