ISO/TR 11069:1995
(Main)Aluminium structures — Material and design — Ultimate limit state under static loading
Aluminium structures — Material and design — Ultimate limit state under static loading
This Technical Report provides design expressions to determine the characteristic values for the ultimate resistances of components and connections of aluminium structures which are subjected to known static forces.
Structures en aluminium — Matériaux et conception — État limite ultime sous charge statique
General Information
Standards Content (Sample)
TECHNICAL IS0
REPORT TR 11069
First edition
1995-09-I 5
Aluminium structures - Material and
design - Ultimate limit state under static
loading
- Matkriaux et conception - Eta t limite u/time
Structures en aluminium
sous charge statique
Reference number
ISO/TR 11069:1995(E)
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SSO/TR 11069:1995(E)
Contents
Page
1
1 Scope .
............................. 1
2 Normative references .
2
.............................................................. .......................
3 Symbols
................. 3
.........................................................
4 Documentation
3
4.1 Calculations .
........... 3
4.2 Testing .
................. 3
Basic design principles .
5
3
...................................................................................
51 . General
3
............................................................ .................
52 . Limit states
................................................................ 4
53 . Design requirement
4
Design load .
5.4
4
Design resistance .
55 .
4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Basic considerations
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
61 . Static actions
............ 5
6.2 Materials .
........... 5
6.3 Geometrical parameters .
............................................................................... 6
6.4 Properties
.................................................................. 7
7 Methods of analysis
7
7.1 General .
............ 7
.............................................................
7.2 Elastic analysis
7
...................................... ........................
7.3 Plastic hinge analysis
7
7.4 Yield line theory .
7
..................................................
7.5 Redundant lattice structures
.......................................... 8
8 Characteristic resistance in tension
................................................................ 8
8.1 Bolted construction
0 IS0 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
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International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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ISO/TR 11069:1995(E)
8.2 Full penetration butt welded construction . 12
9 Characteristic resistance in compression . 13
9.1 Concentric force . 13
...................................................................... 14
9.2 Limiting stress
14
9.3 Normalized slenderness .
9.4 Normalized buckling stress . 15
9.5 Flexural buckling of columns . 15
9.6 Torsional and torsional-flexural buckling of columns . 16
........................................... 18
9.7 Built-up compression members
9.8 Lattice columns . 18
10 Bending . 18
10.1 Moment resistance . 18
.................................................... 19
10.2 Lateral-torsional buckling
....................................................................... 20
11 Beam-columns
Moment with axial compressive force . 20
11.1
11.2 Eccentrically loaded columns . 22
11.3 Shear force in beam-columns and eccentric columns . 23
12 Local buckling . 23
Flat elements in compression . 23
12.1
12.2 Post-buckling strength of flat elements in compression . 26
12.3 Elements with stiffeners . 27
........................................................ 29
12.4 Flat elements in shear
12.5 Curved walls . 32
13 Torsion . 33
13.1 General . 33
13.2 Resistance . 33
Bolted and riveted connections . 34
14
34
14.1 Use of fasteners .
14.2 Spacing of fasteners . 34
14.3 Strength of joints . 36
14.4 Fasteners in tension . 43
. . .
III
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15 Welded connections . 43
15.1 Alloy selection . 43
15.2 Mechanical properties . 44
15.3 Butt joints . 44
15.4 Fillet welds . 44
15.5 Flare groove welds . 50
15.6 Slot and plug welds . 50
15.7 Influence of longitudinal welds on overall strength . 51
15.8 Influence of transverse welds on overall strength . 51
15.9 Influence of welds on local buckling . 51
Annexes
..........................................................................
A Commentary 52
A.1 Introduction . 52
A.2 Scope [clause I] . 52
.......................................
A.3 Basic design principles [clause 51 52
”
..........................................
A.4 Basic considerations [clause 61 53
...........................................
A.5 Methods of analysis [clause 71 56
A.6 Characteristic resistance in tension [clause 81 . 56
A.7 Characteristic resistance in compression [clause 91 . 58
............................................................
A.8 Bending [clause lo] 65
A.9 Beam-columns [clause 1 l] . 68
A.10 Local buckling [clause 121 . 69
A.11 Torsion [clause 131 . 79
A.12 Bolted and riveted connections [clause 141 . 79
A.13 Welded connections [clause 151 . 82
B Bibliography . 85
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ISO/TR 11069:1995(E)
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.
The main task of technical committees is to prepare International Stan-
dards, but in exceptional circumstances a technical committee may pro-
pose the publication of a Technical Report of one of the following types:
- type 1, when the required support cannot be obtained for the publica-
tion of an International Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility
of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International Standard
(“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they can be transformed into Interna-
tional Standards. Technical Reports of type 3 do not necessarily have to
be reviewed until the data they provide are considered to be no longer
valid or useful.
lSO/rR 11069, which is a Technical Report of type 1, was prepared by
Technical Committee ISO/TC 167, Steel and aluminium structures, Sub-
committee SC 3, Aluminium structures.
This Technical Report was proposed as a Draft International Standard but
failed to obtain the required committee support. Reasons for the failure
were primarily concerned with the attempt to promote the standard pre-
pared by the ECCS. There was no serious technical disagreement; thus
the grounds for the lack of support could not be resolved by addressing
the technical content.
Aluminium finds wide application in load-carrying assemblies, such as
building structures, vehicles and ships, to which the rules for strength
design have general validity. This Technical Report deals with the resist-
ance of aluminium structural elements, without regard to any specific
product. Because of this broad target, such standards as those developed
for steel in particular markets cannot provide a model. No single European
standard is suitable for international acceptance; therefore the procedures
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llSO/TR 11069:1995(E)
prese nted are compromises to satisfy the demands of both Europe
and
North America
National standards include the required safety levels for the particular field
treated. Because there is no specific field considered in the Report, there
can be no values given for resistance factors or other safety margins.
However, if the load spectrum and desired reliability are known, safe de-
sign procedures are readily obtained using the resistances provided.
Being intended for international use, no purpose is served by further de-
laying the issuing of the Report by waiting for the final ECCS recommen-
dations, or the conflicting British Standard BS 8118, or the very distant
CEN code for aluminium structures.
Design procedures have been based on the current techniques used for
steel structures, adjusted to suit aluminium, and the presentation will be
familiar to those using modern steel codes of practice, but may differ in
some respects from the methods of earlier aluminium standards.
The Commentary to the Report gives only a limited review of the sources
of the treatments proposed. Over the 16 years that the Committee has
been meeting, a great deal of material has been produced which records
the many aspects of each of the subjects that have been examined, and
reveals the areas where compromise has been needed.
Annexes A and B of this Technical Report are for information only.
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ISO/TR 11069:1995(E)
Limit states design requires a knowledge of the ultimate load capacities
of components and of the distortion of structural assemblies under the
action of specified service loads. These two aspects of structural behav-
iour are in most cases unrelated and require independent treatment.
This Technical Report gives the ultimate load capacity of aluminium
members and connections used in stressed applications, under the action
of static loads. The types of component treated include bars, plates and
panels; the types of connection are riveted, bolted and welded.
Under the action of static loads, some local buckling and local yielding, up
to fully plastic behaviour, are acceptable prior to the attainment of the ul-
timate resistance.
No restriction is placed on the fields of application, as, in this Report, the
component is treated in isolation from its use.
In every application, one design criterion is that the resistance of the part
exceed the load effects. To ensure this in limit states design, the load is
increased by a “partial factor on load” (load factor), and the ultimate re-
sistance of the component is decreased by a “partial factor on
resistance” (resistance factor). These factors, in combination, provide the
desired reliability index for the assembly. As each application has its own
load spectrum and required level of security, no general values for the
partial factors are possible, and are thus not included in this Report.
International Standard IS0 2394 deals with the manner in which suitable
partial factors are to be determined.
Characteristic resistances obtained using this Report are, in general, the
mean of test results less two standard deviations. The values may be
factored to provide “safe”, “working” or “rated” capacities in those ap-
plications which do not use limit states design.
Deformation and natural frequencies of components and assemblies are
limited by the need to meet the dictates of the intended purpose. Such
serviceability requirements are not treated in this Report.
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TECHNICAL REPORT 0 ISO lSO/TR 11069:1995(E)
Aluminium structures - Material and design -
Ultimate limit state under static loading
1 Scope
This Technical Report provides design expressions to determine the characteristic values for the ultimate resist-
ances of components and connections in aluminium assemblies which are subjected to known static forces.
It is intended for general applications of structural aluminium alloys other than those used in aircraft and for other
special purposes. All wrought product types are included, in all thicknesses suitable for load-carrying.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
Technical Report. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreements based on this Technical Report 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 2394: 1986, General principles on reliability for structures.
IS0 3898:1987, Bases for design of structures - Notations - General symbols.
IS0 8930:1987, General principles on reliability for structures - List of equivalent terms.
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ISO/TR 11069:1995(E)
3 Symbols
I Report are based on IS0 3898 and IS0 8930, and are as follows:
The preferred symbols used in this Technica
A area
a dimension, weld throat
b dimension
C constant
distance
: distance, diameter
E
e eccentricity, edge distance elastic modulus
stress
f
F action
normalized buckling stress =fclfo
f
G shear modulus
fastener spacing, gap
g
H length
h web depth
.
I moment of inertia
radius of gyration
K factor
; factor
L length
M
m factor, number moment
N
n number force
r radius R resistance
fastener spacing, stiffener spacing
S
T torque
t thickness
V shear force
V shear flux
W section modulus
W width
x distance
distance
Y
z weld size
factor, index, coefficient of thermal expansion factor, angle
B
6 imperfection
partial factor
8 angle
slenderness
1 normalized slenderness &$‘&) ‘I2 = (I/x) (f,lE) ‘I2
Poisson’s ratio
ratio
P
The following suffixes are used:
b bearing
C compression, critical
design
d
elastic, Euler
e
factored, flange
f
gross
g
h HAZ (heat-affected zone)
k characteristic
I lateral
m maximum, material
n net, normal
limiting
0
plastic, polar
P
r resistance
S shear
t tension, torsion
ultimate
U
weak axis of angles, shear
v
warping, welded, web
W
axis (major)
X
yield, axis (minor)
Y
axis
Z
2
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4 Documentation
4.1 Calculations
Calculations of the resistance of a component or connection shall include the alloy designation and temper, the
guaranteed mechanical properties and any derived properties that are used, together with a complete geometric
description of the component or connection, and the support conditions. Where the resistance is influenced by
associated components, they shall also be fully described.
4.2 Testing
If the resistance is determined by testing, information shall be given on the method of support and load application,
the number of tests, the number of parameters varied, the locations of points where strains or deflections are
measured, the force/displacement relationships, and the mode of failure. Coupons shall be cut from the test
specimens and the mechanical properties determined.
This information shall be sufficiently complete that a third party may interpret the results, and arrive at values for
the characteristic resistances which relate to the probable strengths of the components with the same confidence
as those predicted by the design expressions in this Technical Report.
5 Basic design principles
5.1 General
Components and connections are proportioned to provide a required ultimate resistance, and to perform within
specified limits under service loads. All conditions arising during manufacture, transportation, assembly and con-
struction, and the intended life in service, shall be considered in determining the suitability of the part.
5.2 Limit states
Limit states are classified as “serviceability” limit states and “ultimate” limit states.
Serviceability limit states are dictated by the function of the assembly and are treated in standards specific to the
application.
Ultimate limit states are a matter of public concern. They correspond to the highest force that members, con-
nections, assemblies or complete structures can sustain without uncontrolled distortion. The limit may be set by
the need to avoid
- large deformations due to extensive yielding;
- rupture, including that due to fatigue;
- member instability;
- overall instability.
Deflection and other distortions, except insofar as they influence stability, are not considered at the ultimate limit
state.
While such failure modes as overturning and foundation or anchorage failure need to be considered, they are not
treated in this Technical Report, which is restricted to aluminium parts.
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lSO/TR 11069:1995(E)
5.3 Design requirement
The joints, components and assemblies shall be proportioned to satisfy the inequality:
sd < R,
where
is the design action (internal force) due to the factored load;
sd
is the design resistance (factored resistance).
Rd
5.4 Design load
Knowing the load spectrum for a particular application, characteristic loads are selected, usually based on a re-
quired return period.
The design load, Fd, is the product of the characteristic value of the load, Fk, and the partial factor on load (load
factor), y:
Fd = FkY
Values of 7 are given in the applicable national standards.
The design action (internal force) is obtained from the analysis of the assembly when subjected to the design load
(factored load), and is used to determine the required design resistance (factored resistance) of a component.
The design actions are expressed as follows:
is the design force
Nsd
V is the design shear force
sd
is the design moment
Msd
T is the design torque
sd
5.5 Design resistance
The expressions provided in this Report give the values for the characteristic resistances, R,.
The design resistance (factored resistance), R,, is obtained using
in which J+,., is the partial factor on resistance (resistance factor).
Values of yrn are established for each particular application in conjunction with the partial factors on load (load
factors), y, to provide the required level of reliability. When values are not given in national standards, IS0 2394
provides guidance.
Predictors given in this Report have been targeted to give values for the characteristic resistance that are the mean
value from test results less two standard deviations.
6 Basic considerations
6.1 Static actions
Characteristic values for the actions, to be used in the design, are specified in the standards appropriate to the
application.
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Direct actions are loads such as the weight of cargo,, wind pressure and traffic. They may be static, quasi-static
equivalents of impact forces, temporary, permanent, fixed, variable, planned or accidental. The type of action will
determine, in part, the partial factor to be applied.
Indirect actions are those attributed to imposed changes in geometry such as are caused by expansion and
settlement. In general, indirect load effects are to be avoided by using a suitable overall &sign, as, in normal cir-
cumstances, they are not readily predictable.
6.2 Materials
6.2.1 Aluminium alloys
In selecting an aluminium alloy for a stressed application, its suitability will be assessed on the basis of conformity
to an International Standard, or European or national standard and on the following considerations, as applicable:
- strength: yield and ultimate;
- ductility: elongation and reduction in area;
- weldability and welded properties;
- corrosion resistance in the intended environment;
- formability;
- machinability;
surface finish.
In general, extrusions will be of heat-treated alloys in T5 or higher temper, while sheet and plate may be of heat-
treated or work-hardened alloys.
Where castings or forgings are to be used, there shall be close cooperation with the suppliers to establish the
design properties. For foundry alloys, the values should be confirmed by tests of the finished casting.
6.2.2 Fasteners
Report. Bolts may be of aluminium alloy, zinc- or
Only bolts and solid rivets are treated in this Technical
cadmium-coated steel, or stainless steel. Solid rivets wil preferably be of an aluminium alloy. If proprietary
fasteners are used, the value of the ultimate resistance shal provide the same level of reliability as do connections
proportioned according to this Report (see 6.4.2.1).
6.2.3 Welds
Welding electrodes and filler wire, and shielding gas shall be selected to suit the alloys to be joined and the method
of welding (see clause 15).
6.2.4 Identification of material
All material shall be marked or stored such that the identification of the alloy and temper can be established at all
stages of manufacture.
6.3 Geometrical parameters
Dimensions of profiles, members and overall assemblies shall be subject to the ruling commercial tolerances ap-
plicable to the product
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6.4 Properties
6.4.1 Physical properties
For strength design purposes, all aluminium alloys to which this Report applies shall be considered to have the
following physical properties:
Elastic modulus, E 70 000 MPa
Elastic shear modulus, G 26 000 MPa
0,33
Poisson’s ratio, v
2 700 kg/m3
Density, p
0,000 024 per I “C
Coefficient of thermal expansion, a
6.4.2 Mechanical properties
6.4.2.1 Specified properties
Yield strength, fv, (0,2 % proof stress) is taken to be that stress in tension at which there is a 0,2 % strain offset
in the stress/strain relationship.
Ultimate strength, fu, is the highest force in tension, sustained by the test specimen, divided by the original
cross-sectional area of the specimen.
Yield and ultimate strengths in tension are the basic mechanical properties specified, for each alloy and temper,
in International Standards, or European or national standards. (To satisfy the requirements of the Aluminum As-
sociation, the values are expected to be exceeded in 99 % of the production, at a confidence level of 0,95.)
Selected values of these strengths for some popular alloys are given in tableA.1.
Yield strength in compression, yield and ultimate str .eng ths in shear, and strength in bearing, may be established
by a sufficient number of tests to provide the same leve I of confidence as that for the specified properties. When
these values are not available, 6.4.2.2 shall be used.
6.4.2.2 Derived properties
6.4.2.2.1 Yield strength in compression
In compression, the yield strength shall be taken as the value in tension.
6.4.2.2.2 Yield and ultimate strengths in shear
For direct shear, the characteristic strengths shall be taken to be
- yield strength in shear, J& = 0,6fy
- ultimate strength in shear, fvu = Of&
6.4.2.2.3 Ultimate strength in bearing on fasteners
For bolts and rivets acting in bearing, the characteristic bearing strength of the connected material shall be taken
to be
f
bk = 2fu
This is subject to the further restrictions given in 14.3.2.
The bearing stress on the fastener itself need not be considered.
6
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6.4.2.3 Welded properties
Full account shall be taken of the influence of welding on the properties of aluminium, as described in 8.2.
Table A.1 gives, for some popular alloys, the values of the yield and ultimate tensile strengths of the base metal
and of the metal in the heat-affected zone (HAZ) at the weld, which are acceptable for design purposes.
TableA. gives, for some popular alloys, values for the ultimate tensile strengths of the weld beads which are
acceptable for design purposes.
Higher values may be used if they are demonstrated and can be ensured in production.
When the properties of the heat-affected zone (HAZ) are not known, they may be taken to be equal to those in
the solution-treated condition for heat-treated alloys and equal to those in the annealed condition for work-
hardened alloys. Because the properties of the weld bead are a function of both the base metal alloy and the filler
wire alloy, any combination for which the properties are not known shall be tested to establish the strength of the
weld bead itself.
7 Methods of analysis
7.1 General
For individual components and connections, the design expressions in this Report give the ultimate resistance.
Behaviour may be linear or non-linear. The values obtained are not related to the method of analysis; however, as
the behaviour of individual parts can influence the overall behaviour of the assembly, the method of analysis may
take cognizance of the force/deformation relationships of the components.
7.2 Elastic analysis
Elastic analysis is generally considered to provide a lower bound solution, and is permitted for all assemblies,
without regard for the behaviour of the individual components up to the ultimate resistance, unless geometric
distortions influence the stability of the assembly.
7.3 Plastic hinge analysis
Plastic hinge analysis may be used for rigid frames in which it can be demonstrated that the required rotation at
the yield hinges is available, and the destabilizing influence of compression forces is taken into account. The limited
shall be considered when determining whether plastic
deformation capacity at bolted joints and transverse welds _
hinges can be developed.
7.4 Yield line theory
Yield line theory for plates may be used, but full account shal be taken of the influence of any welds or perfor-
ations for fasteners.
7.5 Redundant lattice structures
Non-linear analysis of redundant lattice structures is permitted only where the force/deformation relationships for
the components are k nown and can be accurately or conservatively modelled.
7
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ISO/TR 11069:1995(E)
8 Characteristic resistance in tension
8.1 Bolted construction
8.1 .l
Concentric force
For a member subjected to a concentric axial tension force, the resistance is the lesser of the values given by
Nk =A&
Nk = A,k6i
where
is the tensile yield strength (0,2 % proof stress) of the mate
...
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