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Base Isolator Testing
Earthquake Engineering Postgraduate Research Department of Civi l Engineering, Shanghai University
March 2011
Standards, Outputs and Data Sheets
Background
In 1999 TC45 meeting at Budapest, Italy made a NEW WORK ITEM PROPOSAL regarding ISO specification related to design rules of “Elastomeric Isolators” for seismic protection of structures.
In 2000 TC45 meeting Kuala Lumpur, Japan proposed a working draft of product-specification and test methods for “Elastomeric seismic-protection isolators”. Working group 9 under TC45/SC4 (WG9) was composed for the development of specifications. Japan was nominated as the organizer. (Prof. NISHI).
In July 2005, ISO 22762 was issued.
In 2006 TC45 at San Francisco (USA), revised the ISO 22762:2005 which was started by WG9.
In 2010 TC45 at Haarlem (Netherland), the 2nd version of ISO 22762 was completed and was issued on November 2010 .
Background
Members of the Working Group WG9
Canada, China, Czech, India, Japan, Malaysia, Thailand, United Kingdom, United States of America.
Japan was nominated as the organizer of the Working Group.
The International Meeting that took place
1999 at Budapest/Hungary, 2000 at Kuala Lumpur/Malaysia, 2001 at Goa/India, 2002 at Kyoto/Japan, 2003 at Bangkok/Thailand, 2004 at London/UK, 2005 at Berlin/Germany where the work was completed.
The Official issue date was July 15, 2005. ISO 22762-2010 (2nd Version) was issued on November 1,2010
The new version had technical changes in classification, design and rules based on the technical progress since 2005
It had minor editorial changes in symbols and definitions.
ISO 22762Elastomeric Seismic-Protection Isolators
The construction of ISO 22762
Elastomeric Seismic-Protection Isolators
Important Definitions
Hysteresis Loop: This is the force displacement plot generated by the shear testing of an isolator.
Elastic Stiffness, Ke: This is the initial stiffness of the isolator, typically at less than one inch displacement. Its value is dominated by the lead core size and is important in controlling the response to service loads such as wind.
Yielded Stiffness, Kd or K2: This is the secondary stiffness of the isolator and is a function of the modulus, total height and are of the rubber.
Keff (Effective Stiffness): This is the isolator force divided by the displacement. This is a displacement independent quantity.
Hysteretic Strength, Qd: This is the force axis intercept of the isolator hysteresis loop. This parameter relates to damping and isolator response to service loads.
Yield Force, Fy: the yield force is the point in the model at which
the initial stiffness changes to the secondary stiffness. In realty there is a
smooth transition from one stiffness to another, rather than a well defined
point. This value is mainly used in analytical modeling.
Energy Dissipated per Cycle, EDC: This is the area of the
hysteresis loop. This value is a measure for the damping
of the isolator.
Hysteresis Loop
The Types of Elastomeric Isolators
Elastomeric Seismic-Protection Isolators
Linear Natural Rubber Bearing
(NRB)
Lead Rubber Bearing (LRB)
The Types of Elastomeric Isolators
Elastomeric Seismic-Protection Isolators
High Damping Rubber Bearings
Force-Displacement Loop of High Damping Rubber Bearing
(Hysteresis Loop)
Elastomeric Isolators
Test MethodsRubber Material Testing
Tensile test Aging Test Hardness Adhesion Property Shear Property
Isolator Testing
Compression-Shear Test Compression Test Various dependence Test Ultimate Property Durability Property
Strain Dependency Compressive Force
Dependency Frequency Dependency Repeated Deformation
Dependency Temperature Dependency
Durability Tests
Degradation Test Creep Test Fatigue Test
Various Dependency Tests
Elastomeric Isolators
Required Tests For Isolators According to ISO 22762
Type Test Assure Design Properties at
development Prequalification test Proto-type test
Previous test results are available
Routine Test
Quality Control test for individual projects
Elastomeric Isolators
Type Test Item and Specimen Scale A
Circular Dia.>150 mm
Rect. Side >100mm
Scale B
Circular Dia.>500mm
Rect. Side >500mm
Rubber th.>1.5mm
Plate th.>0.5mm
STD
Standard Specimen
ISO 22762-1, tables 9-1,
And 9-2
SBS
Shear block specimen
ISO 22762-1, 5.8.3
Elastomeric Isolators
Compression-Shear Testing
Compression-Shear Testing of Elastomeric Isolators
Elastomeric Isolators
Compression-Shear Testing
1 2
1 2h
Q QK
X X
2
1 2
2eq
h
Wh
K X X
1 1 2 2
1 2
1
2d d
d
Q Q Q QK
X X
1 2
2d d
d
Q QQ
Shear Stiffness
Equivalent Damping Ratio
Post-Yielding Stiffness
Characteristic Strength
1 2
1 2v
P PK
Y Y
Compressive Stiffness
1 01P P
1 01P P
Elastomeric Isolators
Tensile Property Testing
Test on Tensile Property
Relation of Tensile Stress and Shear StrainTest Specimen
In the tests of the large scale, the failure was observed at the tensile strain of 50% and shear strain of 300%.
Results of the large scale isolator was much less than expected limit of the small scale isolator.
There is a large difference in the failure limit due to the scale effect.
The design creteria as shown is the region less than 10% tensile strain and the region less than 300% shear strain.
Elastomeric IsolatorsDependency Testing Examples
HDR Frequency Dependency (Damping Ratio)HDR Frequency Dependency (Shear Strain)
Shear Strain Dependency (Damping Ratio)Shear Strain Dependency (Damping Ratio)
Elastomeric IsolatorsTesting of Rubber Reinforcement
Elastomeric IsolatorsTesting of Rubber Reinforcement
Elastomeric IsolatorsIsolator Grometrical Properties
Elastomeric IsolatorsIsolator Design Properties
The axial capacities provided correspond to maximum displacement based on design limits of 250% rubber shear strain or 2/3 the isolator diameter.
An isolators actual displacement and load capacity are dependent on the rubber modulus and number of rubber layers.
Rubber shear moduli (G) are available from 0.38 N/mm² to 0.70 N/mm².
Elastic Stiffness (Ke) for analytical modeling may be taken as 10-times the yielded stiffness (Kd).
Kd range shown in the table is typical for most projects, Kd values up to three times the maximum shown in the range can be achieved by limiting the displacement capacity to 2/3 of the shown value.
Elastomeric IsolatorsDesigner Notes on Isolator Design Properties
Thank You for your Attention
Earthquake Engineering Postgraduate Research Department of Civi l Engineering, Shanghai University
March 2011