ISO 22762-2:2005

Elastomeric seismic-protection isolators — Part 2: Applications for bridges — Specifications

ISO 22762 applies to elastomeric seismic isolators used to provide buildings or bridges with protection from earthquake damage. The isolators covered consist of alternate elastomer layers and reinforcing steel plates. They are placed between a superstructure and its substructure to provide both flexibility for decoupling structural systems from ground motion, and damping capability to reduce displacement at the isolation interface and the transmission of energy from the ground into the structure at the isolation frequency. ISO 22762-2:2005 specifies the requirements for elastomeric seismic isolators used for bridges and the requirements for the rubber material used in the manufacture of such isolators. The specification covers requirements, design rules, manufacturing tolerances, marking and labelling and test methods for elastomeric isolators.

Appareils d'appuis structuraux en élastomère pour protection sismique — Partie 2: Applications pour ponts — Spécifications

General Information

• Status: Withdrawn
• Publication Date: 21-Jul-2005
• Withdrawal Date: 21-Jul-2005
• ICS: 83.140.99 - Other rubber and plastics products
• ICS: 93.040 - Bridge construction
• Technical Committee: ISO/TC 45/SC 4 - Products (other than hoses)
• Drafting Committee: ISO/TC 45/SC 4/WG 9 - Elastomeric isolators
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 21-Oct-2010

Relations

• Revised: ISO 22762-2:2010 - Elastomeric seismic-protection isolators — Part 2: Applications for bridges — Specifications
• Effective Date: 12-May-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22762-2
First edition
2005-07-15


Elastomeric seismic-protection
isolators —
Part 2:
Applications for bridges — Specifications
Appareils d'appuis structuraux en élastomère pour protection
sismique —
Partie 2: Applications pour ponts — Spécifications




Reference number
ISO 22762-2:2005(E)
©
ISO 2005

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ISO 22762-2:2005(E)
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ii © ISO 2005 – All rights reserved

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ISO 22762-2:2005(E)
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviated terms . 4
5 Classification. 8
5.1 General. 8
5.2 Classification by construction . 8
5.3 Classification by ultimate properties. 9
5.4 Classification by tolerance on shear stiffness .9
6 Requirements . 9
6.1 General. 9
6.2 Type tests and routine tests . 10
6.3 Functional requirements. 10
6.4 Design compressive force and design shear displacement . 11
6.5 Product performance requirements. 11
6.6 Rubber material requirements. 17
6.7 Dimensional requirements. 19
6.8 Requirements on steel used for flanges and reinforcing plates . 19
7 Design rules . 19
7.1 General rules . 19
7.2 Shape factor . 21
7.3 Compressive and shear properties. 22
7.4 Shear strain due to horizontal displacements. 22
7.5 Total local shear strain. 23
7.6 Tensile stress on reinforcing steel plates. 23
7.7 Stability . 24
7.8 Force, moment and deformation affecting structures. 25
7.9 Design of fixings . 26
8 Manufacturing tolerances . 27
8.1 General. 27
8.2 Measuring instruments . 27
8.3 Plan dimensions of isolator body . 27
8.4 Product height. 28
8.5 Flatness of products. 31
8.6 Horizontal offset. 31
8.7 Plan dimensions of flanges . 32
8.8 Flange thickness. 32
8.9 Tolerances on positions of flange bolt holes . 33
9 Marking and labelling . 33
9.1 General. 33
9.2 Information to be provided . 33
9.3 Additional requirements . 34
9.4 Marking and labelling examples. 34
10 Test methods. 34
11 Quality assurance. 34
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ISO 22762-2:2005(E)
Annex A (normative) Tensile stress in reinforcing steel plate . 35
Annex B (normative) Buckling stability . 37
Annex C (normative) Allowable tensile stress in isolator . 38
Annex D (informative) Confirmation list. 39
Annex E (informative) Dependency of ultimate properties on shape factor . 41
Annex F (informative) Minimum recommended properties of elastomers . 44
Annex G (informative) Compressive stiffness. 45
Annex H (informative) Determination of shear properties of elastomeric isolators. 48
Annex I (informative) Determination of local shear strain due to compression . 53
Annex J (informative) Maximum compressive stress. 56
Bibliography . 57

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ISO 22762-2:2005(E)
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 22762-2 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 4, Products (other than hoses).
ISO 22762 consists of the following parts, under the general title Elastomeric seismic-protection isolators:
 Part 1: Test methods
 Part 2: Applications for bridges — Specifications
 Part 3: Applications for buildings — Specifications
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ISO 22762-2:2005(E)
Introduction
This International Standard contains two parts related to specifications for isolators — one for bridges and the
other for buildings — since the requirements for isolators for bridges and for buildings are quite different,
although the basic concept of the two products is similar. Therefore, when this International Standard is
applied to the design of bridge isolators, Part 2 and the relevant clauses in Part 1 are used and, when it is
applied to building isolators, Part 3 and the relevant clauses in Part 1 are used.
The main differences to be noted between isolators for bridges and isolators for buildings are as below:
a) Isolators for bridges are mainly rectangular in shape and those for buildings circular in shape.
b) Isolators for bridges are designed to be used for both rotation and horizontal displacement, while isolators
for buildings are designed for horizontal displacement only.
c) Isolators for bridges are designed to perform on a daily basis to accommodate length changes of bridges
caused by temperature changes as well as during earthquakes, while isolators for buildings are designed
to perform only during earthquakes.
d) Isolators for bridges are designed to withstand dynamic loads caused by vehicles on a daily basis as well
as earthquakes, while isolators for buildings are mainly designed to withstand dynamic loads caused by
earthquakes only.
For structures that are neither buildings nor bridges (e.g. tanks), the structural engineer may use either Part 2
or Part 3 of this International Standard, depending on the requirements of the structure.
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INTERNATIONAL STANDARD ISO 22762-2:2005(E)

Elastomeric seismic-protection isolators —
Part 2:
Applications for bridges — Specifications
1 Scope
ISO 22762 applies to elastomeric seismic isolators used to provide buildings or bridges with protection from
earthquake damage. The isolators covered consist of alternate elastomer layers and reinforcing steel plates.
They are placed between a superstructure and its substructure to provide both flexibility for decoupling
structural systems from ground motion, and damping capability to reduce displacement at the isolation
interface and the transmission of energy from the ground into the structure at the isolation frequency.
This part of ISO 22762 specifies the requirements for elastomeric seismic isolators used for bridges and the
requirements for the rubber material used in the manufacture of such isolators. The specification covers
requirements, design rules, manufacturing tolerances, marking and labelling and test methods for elastomeric
isolators.
Some items of classification and some requirements need to be confirmed before production and these should
be reviewed using the list given in Annex D.
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, Structural steels — Plates, wide flats, bars, sections and profiles
ISO 1052, Steels for general engineering purposes
ISO 1629, Rubber and latices — Nomenclature
ISO 3302-1, Rubber — Tolerances for products — Part 1: Dimensional tolerances
ISO 22762-1:2005, Elastomeric seismic-protection isolators — Part 1: Test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
breaking
rupture of elastomeric isolator due to compression (or tension)-shear loading
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ISO 22762-2:2005(E)
3.2
buckling
state when elastomeric isolators lose their stability under compressive-shear loading
3.3
compressive properties of elastomeric isolator
compressive stiffness (K ) for all types of rubber bearings
v
3.4
compressive-shear testing machine
machine used to test elastomeric isolators, which has the capability of shear loading under constant
compressive load
3.5
cover rubber
rubber wrapped around the outside of inner rubber and reinforcing steel plates before or after curing of
elastomeric isolators for the purpose of protecting the inner rubber from deterioration due to oxygen, ultraviolet
rays and other natural elements and protecting the reinforcing plates from corrosion
3.6
design compressive stress
long-term compressive force on the elastomeric isolator imposed by the structure
3.7
effective loaded area
area sustaining vertical load in elastomeric isolators, which corresponds to the area of reinforcing steel plates
3.8
effective width
〈rectangular elastomeric isolator〉 the smaller of the two side lengths of inner rubber to which direction shear
displacement is not restricted
3.9
elastomeric isolator
rubber bearing, for seismic isolation of buildings, bridges and other structures, which consists of multi-layered
vulcanized rubber sheets and reinforcing steel plates
NOTE Types of such isolators include high-damping rubber bearings, linear natural rubber bearings and lead rubber
bearings.
3.10
first shape factor
ratio of effectively loaded area to free deformation area of one inner rubber layer between steel plates
3.11
high-damping rubber bearing
HDR
elastomeric isolator with relatively high-damping properties obtained by special compounding of the rubber
and the use of additives
3.12
inner rubber
rubber between multi-layered steel plates inside an elastomeric isolator
3.13
lead rubber bearing
LRB
elastomeric isolator whose inner rubber with a lead plug or lead plugs press fitted into a hole or holes of the
isolator body to achieve damping properties
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ISO 22762-2:2005(E)
3.14
linear natural rubber bearing
LNR
elastomeric isolator with linear shear force-deflection characteristics and relatively low-damping properties and
fabricated using natural rubber
NOTE Any bearing with relatively low damping may be treated as an LNR bearing for the purposes of isolator testing.
3.15
maximum compressive stress
maximum compressive stress acting briefly on elastomeric isolators during an earthquake
3.16
nominal compressive stress
long-term compressive stress recommended by the manufacturer for the isolator, including the safety margin
3.17
roll-out
instability of an isolator with either dowelled or recessed connection under shear displacement
3.18
routine test
a test for quality control of the production isolators during and after manufacturing
3.19
second shape factor
〈circular elastomeric isolator〉 ratio of the diameter of the inner rubber to the total thickness of the inner rubber
〈rectangular or square elastomeric isolator〉 ratio of the effective width of the inner rubber to the total thickness
of the inner rubber
3.20
shear properties of elastomeric isolators
a comprehensive term that covers characteristics determined from isolator tests:
 shear stiffness (K ) for LNR;
h
 shear stiffness (K ) and equivalent damping ratio (h ) for HDR and LRB;
h eq
 post-yield stiffness (K ) and characteristic strength (Q ) for LRB.
d d
3.21
structural engineer
engineer who is in charge of designing of structure for base-isolated bridges or buildings and is responsible for
specifying the requirements for elastomeric isolators
3.22
type test
test for verification either of material properties and isolator performances during development of the product
or that project design parameters are achieved
3.23
ultimate properties
properties at either buckling, breaking, or roll-out of an isolator under compressive-shear loading
3.24
ultimate property diagram
UPD
diagram giving the interaction curve of compressive stress and buckling strain or breaking strain of an
elastomeric isolator
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ISO 22762-2:2005(E)
4 Symbols and abbreviated terms
For the purposes of all three parts of ISO 22762, the symbols given in Table 1 apply.
Table 1 — Symbols and definitions
Symbol Definition
A effective plan area; plan area of elastomeric isolator excluding cover rubber portion
A
effective area of bolt
b
A overlap area between the top and bottom elastomer area of isolator sheared under non-seismic
e
displacement
A
load-free area of isolator
free
A
loaded area of isolator
load
A
p area of the lead plug for a lead rubber bearing
a
side length of square elastomeric isolator excluding cover rubber thickness, or length in
longitudinal direction of rectangular isolator excluding cover rubber thickness
a length of the shorter side of the rectangular isolator including cover rubber thickness
e

a' length in longitudinal direction of the rectangular isolator, including cover rubber thickness
B effective width for bending of flange
b length in transverse direction of the rectangular isolator, excluding cover rubber thickness
b' length in transverse direction of the rectangular isolator, including cover rubber thickness
c
distance from centre of bolt hole to effective flange section
D' outer diameter of circular isolator, including cover rubber
D
diameter of flange
f
d
inner diameter of reinforcing steel plate
i
d
diameter of bolt hole
k
d
outer diameter of reinforcing steel plate
o
E
ap apparent Young’s modulus of bonded rubber layer
E
apparent Young’s modulus corrected, if necessary, by allowing for compressibility
c
s
apparent Young’s modulus corrected for bulk compressibility depending on the shape factor (S )
E 1
c

E
bulk modulus of rubber
∞
E
Young’s modulus of rubber
0
F
tensile force on isolator by uplift
u
G
shear modulus
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ISO 22762-2:2005(E)
G γ equivalent linear shear modulus at shear strain γ
( )
eq
H height of elastomeric isolator including mounting flange
H
height of elastomeric isolator excluding mounting flange
n
h
eq equivalent damping ratio
h γ
( )
eq equivalent damping ratio as a function of shear strain
K
post-yield stiffness (tangential stiffness after yielding of lead plug) of lead rubber bearing
d
K
shear stiffness
h
K
initial shear stiffness
i

K
p shear stiffness of lead plug inserted in lead rubber bearing
K
shear stiffness of lead rubber bearing before inserting lead plug
r
K
tangential shear stiffness
t

K
compressive stiffness
v
L
length of one side of a square flange
f
M resistance to rotation
M
moment acting on bolt
f
M
moment acting on isolator
r
n
number of rubber layers
n
number of fixing bolts
b
P compressive force
P
design compressive force
0

P
maximum design compressive force
max
P
minimum design compressive force
min
Q
shear force
Q
shear force at break
b
Q
shear force at buckling
buk
Q
characteristic strength
d
S
first shape factor
1
S
second shape factor
2
T temperature
T total rubber thickness, given by T = nt×
r r r
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ISO 22762-2:2005(E)
t
thickness of one rubber layer
r
tt,
thickness of rubber layer laminated on each side of plate
r1 r2
t
thickness of one reinforcing steel plate
s
t
thickness of outside cover rubber
o
U γ
( ) function giving ratio of characteristic strength to maximum shear force of a loop

V
uplift force
v
loading velocity
W
energy dissipated per cycle
d
X shear displacement
X
design shear displacement
0

X
shear displacement at break
b
X
shear displacement at buckling
buk
X
shear displacement due to quasi-static shear movement
s

X
maximum design shear displacement
max
X
shear displacement due to dynamic shear movement
d
Y compressive displacement
Z section modulus of flange
α
coefficient of linear thermal expansion

γ
shear strain
γ
design shear strain
0
γ
upper limit of the total of design strains on elastomeric isolators
a
γ
shear strain at break
b
γ
local shear strain due to compressive force
c
γ
shear strain due to dynamic shear movement
d

γ
maximum shear strain during earthquake
max
γ
local shear strain due to rotation
r
γ
shear strain due to quasi-static shear movement
s
γ
ultimate shear strain
u
δ
horizontal offset of isolator
H
δ
difference in isolator height measured between points located at a 180° angle
V
ε
compressive strain of isolator
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ISO 22762-2:2005(E)
ε
creep strain
cr

ε
tensile strain of isolator
T
ε
tensile-break strain of isolator
Tb
ε
Ty tensile-yield strain of isolator
ζ
ratio of total rubber height to total height of rubber and steel layers
θ
rotation angle of isolator about the diameter of a circular bearing or about an axis through a
rectangular bearing
θ
rotation angle of isolator in the longitudinal direction (a)
a
θ
rotation angle of isolator in the transverse direction (b)
b
λ
correction factor for calculation of stress in reinforcing steel plates
η
correction factor for calculation of critical stress
κ correction factor for apparent Young’s modulus according to hardness
Σγ
total local shear strain
σ
compressive stress in isolator
σ
design compressive stress
0
σ
tensile stress in bolt
B
σ
bending stress in flange
b
σ
allowable bending stress in steel
b
f
σ
critical stress in isolator
cr
σ
allowable tensile stress in steel
f
σ
maximum design compressive stress
max
σ
minimum design compressive stress
min
σ
for building: nominal long term compressive stress recommended by manufacturer
nom
σ
tensile stress in reinforcing steel plate
s
σ
allowable tensile stress in steel plate
sa

σ
sy yield stress of steel for flanges and reinforcing steel plates
σ
tensile strength of steel for flanges and reinforcing steel plates
su
σ
tensile stress
t
σ
allowable tensile stress in isolator
te

σ
yi yield stress in steel plate
τ
shear stress in bolt
B
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ISO 22762-2:2005(E)
τ
allowable shear stress in steel
f
φ
factor for computation of buckling stability
ψ
factor for computation of buckling check
ξ
factor for computation of critical stress
5 Classification
5.1 General
Elastomeric isolators are classified by construction, their ultimate properties, and tolerances on their
performance.
5.2 Classification by construction
Elastomeric isolators are classified by construction as shown in Table 2. The structural engineer shall specify
which construction is to be used.
Table 2 — Classification by construction
Mounting flanges are
bolted to connecting
flanges, which are
Type I
bonded to the laminated
rubber.

Mounting flanges are
Type II directly bonded to the
laminated rubber.

Isolators without
Type III
mounting flanges.


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ISO 22762-2:2005(E)
5.3 Classification by ultimate properties
Elastomeric isolators may be classified by their ultimate properties as shown in Table 3. The ultimate
properties are defined as the compressive stress and the shear strain when the isolator reaches the ultimate
state. For Type I and Type II isolators, the ultimate state of the isolator is defined as either buckling or
breaking. The structural engineer shall specify the ultimate properties required.
Table 3 — Classification by ultimate properties
Compressive stress
Ultimate shear strain γ , %
u
induced by dead load,
2
N/mm γ W 300 % 250 % u γ < 300 % 200 % u γ < 250 % γ < 200 %
u u u u
6,0 A1 B1 C1 D1
8,0 A2 B2 C2 D2
10,0 A3 B3 C3 D3
12,0 A4 B4 C4 D4

NOTE In the selection of isolators for a particular project, the ultimate shear performance under both maximum
compressive stress and minimum compressive stress needs to be considered. The Table 3 classification provides a guide
for bolted isolators in situations where the minimum stress is not tensile.
The ultimate properties depend on the shape of the isolator and therefore the classification should be
determined considering the shape factors as discussed in Annex E.
5.4 Classification by tolerance on shear stiffness
Elastomeric isolators are classified by tolerance on shear stiffness as shown in Table 4. The structural
engineer shall specify the tolerance required.
Table 4 — Classification by tolerance on shear stiffness
Class Tolerance
S-A ± 10 %
S-B
± 20 %
6 Requirements
6.1 General
Elastomeric isolators for bridges and the materials used in their manufacture shall meet the requirements
specified in this clause. For test items (see Table 5) that have no specific required values, the manufacturer
shall define the values and inform the purchaser prior to production.
The standard temperature for determining the properties of elastomeric isolators is 23 °C in accordance with
prevailing International Standards. However, it is advisable to establish a range of working temperatures
taking into consideration actual environmental temperatures and possible changes in temperature at the work
site where the elastomeric isolators are installed.
© ISO 2005 – All rights reserved
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