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