ISO 8686-1:2012

INTERNATIONAL ISO
STANDARD 8686-1
Second edition
2012-12-15
Cranes — Design principles for loads
and load combinations —
Part 1:
General
Appareils de levage à charge suspendue — Principes de calcul des
charges et des combinaisons de charge —
Partie 1: Généralités
Reference number
©
ISO 2012
© ISO 2012
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ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 General . 2
5.1 General principles . 2
5.2 Methods of proof of competence calculations . 3
5.3 Assessment of loads . 3
5.4 Categories of loads . 4
6 Loads and applicable factors . 4
6.1 Regular loads . 4
6.2 Occasional loads. 9
6.3 Exceptional loads .10
6.4 Miscellaneous loads .13
7 Principles of choice of load combinations .13
7.1 Basic considerations .13
7.2 Load combinations during erection, dismantling and transport .17
7.3 Application of Table 3 .17
7.4 Partial safety factors for the proof of rigid body stability .20
Annex A (normative) Application of allowable stress method and limit state method of design .21
Annex B (informative) General guidance on application of dynamic factors ϕ .26
Annex C (informative) Example of model for estimating value of dynamic factor ϕ for cranes
travelling on rails .27
Annex D (informative) Example of determination of loads caused by acceleration .31
Annex E (informative) Example of method for analysing loads due to skewing .40
Annex F (informative) Illustration of types of hoist drives
........................................................................................................46
Bibliography .49
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 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 8686-1 was prepared by Technical Committee ISO/TC 96, Cranes, Subcommittee SC 10, Design —
Principles and requirements.
This second edition cancels and replaces the first edition (ISO 8686-1:1989), which has been
technically revised.
ISO 8686 consists of the following parts, under the general title Cranes — Design principles for loads and
load combinations:
— Part 1: General
— Part 2: Mobile cranes
— Part 3: Tower cranes
— Part 4: Jib cranes
— Part 5: Overhead travelling and portal bridge cranes
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 8686-1:2012(E)
Cranes — Design principles for loads and load
combinations —
Part 1:
General
1 Scope
This part of ISO 8686 establishes general methods for the calculating loads and principles to be used
in the selection of load combinations for proofs of competence in accordance with ISO 20332 for the
structural and mechanical components of cranes as defined in ISO 4306-1.
It is based on rigid body kinetic analysis and elastostatic analysis but expressly permits the use of more
advanced methods (calculations or tests) to evaluate the effects of loads and load combinations, and
the values of dynamic load factors, where it can be demonstrated that these provide at least equivalent
levels of competence.
This part of ISO 8686 provides for two distinct kinds of application:
a) the general form, content and ranges of parameter values for more specific standards to be developed
for specific types of cranes;
b) a framework for agreement on loads and load combinations between a designer or manufacturer
and a crane purchaser for those types of cranes where specific standards do not exist.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 4302, Cranes — Wind load assessment
ISO 4306 (all parts), Lifting appliances — Vocabulary
ISO 4310, Cranes — Test code and procedures
ISO 20332, Cranes — Proof of competence of steel structures
3 Terms and definitions
For the purposes of this document, the definitions given in ISO 4306 and the following apply.
3.1
load or loads
external or internal actions in the form of forces, displacements or temperature, which cause stresses in
the structural or mechanical components of the crane
3.2
analysis
study of the movement and the inner forces of systems modelled by elements that are
assumed to be non-elastic
3.3
analysis
study of the relative elastic displacements (distortion), movement and the inner forces
of systems modelled by elements that are assumed to be elastic
4 Symbols
The main symbols used in this part of ISO 8686 are given in Table 1.
Table 1 — Main symbols
Symbol Description Reference
ϕ Factors for dynamic effects Various
ϕ Factors for hoisting and gravity effects acting on the mass of the crane 6.1.1
ϕ Factor for hoisting a grounded load 6.1.2.1
ϕ Factor for dynamic effects of sudden release of part of load 6.1.2.2
ϕ Factor for dynamic effects of travelling on an uneven surface 6.1.3.2
ϕ Factor for dynamic loads arising from acceleration of crane drives 6.1.4
ϕ Factor for effects of dynamic load tests 6.3.2
ϕ Factor for elastic effects arising from collision with buffers 6.3.3
ϕ Factor for dynamic effects from unintentional loss of payload 6.3.5
HC1 to HC4 Hoisting classes assigned to cranes 6.1.2.2 to 6.1.2.1.4
6.1.2.1.1 to
β Factor assigned to hoisting class
6.1.2.1.2; 6.1.2.1.5
β Term used in determining the value of ϕ 6.1.2.2
3 3
6.1.2.1.3
v Steady hoisting speed, in metres per second
h
(Table 2b)
F , F , F Buffer forces 6.3.3, Annex D
x x2 x4
7.3.2, Table 3, A.2
γ Coefficients for calculating allowable stresses
f
to A.3
7.3.3, Table 3,
γ Partial safety factor 7.3.7.2, 7.3.8, A.2
p
to A.3
γ Resistance coefficient Table 3, Annex A
m
γ Coefficient for high-risk applications 7.3.6, Annex A
n
m Mass of pay load 6.1.2.2
6.1.2.1.1, 6.1.2.3,
m Mass of the gross load
H
6.3.1, Annex D
ηm = m − Δm Mass of that part of the hoist load remaining suspended from the crane 6.3.1
H H
NOTE Further symbols are used in the annexes and are defined therein.
5 General
5.1 General principles
The objective of proof of competence calculations carried out in accordance with this part of ISO 8686
is to determine mathematically that a crane will be competent to perform in practice when operated in
compliance with the manufacturer’s instructions.
2 © ISO 2012 – All rights reserved

The basis for such proof against failure (e.g. by yielding, elastic instability or fatigue) is the comparison
between calculated stresses induced by loads and the corresponding calculated strengths of the
constituent structural and mechanical components of the crane.
Proof against failure may also be required in respect of overturning stability. Here, the comparison is
made between the calculated overturning moments induced by loads and the calculated resistance to
overturning provided by the crane. In addition, there may be limitations on forces that are necessary
to ensure the stability and/or to avoid unwanted displacement of portions of the crane or of the crane
itself, for example, the jib support ropes becoming unloaded or the crane sliding.
The effects of differences between actual and ideal geometry of mechanical and structural systems (e.g.
the effect of tolerances, settlements, etc.) shall be taken into account. However, they shall be included
specifically in proof of competence calculations only where, in conjunction with applied loads, they may
cause stresses that exceed specified limits.
When applying this part of ISO 8686 to the different types of cranes, operating in the same service and
environmental conditions, equivalent resistance to failure should be sought.
5.2 Methods of proof of competence calculations
There are two general approaches to structural design or proof of competence.
a) The allowable stress method: where the design stresses induced by combined loads are compared
with allowable stresses established for the type of member or condition being examined. The
assignment of allowable stress is made on the basis of service experience with consideration for
protection against failure due, for example, to yielding, elastic instability or fatigue.
b) The limit state method: where partial safety factors are used to amplify loads before they are
combined and compared with the limit states imposed, for example, by yielding or elastic instability.
The partial safety factor for each load is established on the basis of probability and the degree of
accuracy with which the load can be determined. Limit state values comprise the characteristic
strength of the member reduced to reflect statistical variations in its strength and geometric
parameters. This method is a prerequisite if this part of ISO 8686 is applied together with ISO 20332
and/or the 2nd order method.
Annex A gives a more detailed description
...