1 Base Isolation Base isolation is a technique of controlling structural response in which the building or structure is decoupled from the horizontal components of the earthquake ground motion by interposing a layer with low horizontal stiffness between the structure and the foundation. This layer gives the structure a fundamental frequency that is much lower than its fixed-base frequency and also much lower than the predominant frequencies of the ground motion. The isolation system does not absorb the earthquake energy, but rather deflects it through the dynamics of the system.

2 Displacement and Acceleration Spectra

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4 Concept of Seismic Isolation

5 Without base isolation With base isolation

6 Seismic Isolators Rubber Steel plates 1.Laminated Rubber Bearings  The bearing is very stiff and strong in the vertical direction, but flexible in the horizontal direction xbxb ybyb kbkb cbcb cbcb kbkb Mathematical model

7 2.Lead Rubber Bearings ybyb cbcb xbxb kbkb cbcb kbkb  The lead plug reduces, or dissipates, the energy of motion - i.e., kinetic energy, by converting that energy into heat.

8 Lead Rubber Bearing at Building Site

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10 3.Friction Pendulum Bearings

11 Slider 1.The building is supported by bearing pads that have a curved surface and low friction. 2.During an earthquake, the building is free to slide on the bearings. Friction Pendulum Bearings

12 BHUJ HOSPITAL PROJECT

13 Bhuj District Hospital, India - completed January 2003

14 Lead Rubber Bearing being Lowered into Position

15 Lead Rubber Bearing on Site, Bhuj District Hospital, India 2002

16 Lead Rubber Bearings, Bhuj District Hospital, India 2002

17 PARLIAMENT NEW ZEALAND