Base Isolated Buildings

Topics: Earthquake, Earthquake engineering, Base isolation Pages: 3 (663 words) Published: April 2, 2014
 BASE ISOLATED BUILDINGS

What is base isolation?
When a building is built away (isolated) from the ground, resting on flexible bearings or pads known as base isolators. It is of the most popular means of protecting a structure against earthquake forces.

HISTORY
The first evidence of architects using the principle of base isolation for earthquake protection was discovered in Pasargadae. One of the world's first base-isolated structures – the William Clayton building

Base Isolation System
Major types of base isolator systems
High damping rubber bearings
Elastomeric based Isolator systems
Lead rubber bearings

Elastomeric based Isolator systems
Elastomeric bearings have multiple layers of steel shim and rubber laminated together under high pressure and heat in a mold. High damping rubber bearings
As an alternative to Elastomeric bearings, HDRB’s provide critical damping from 10% to 20% at 100% shear strains. Lead rubber bearings
LRB are Elastomeric bearings that contain one or more lead plugs inserted into performed holes.

Lead
Lead is chosen because of its plastic property – it may deform with the movement of the earthquake, it will revert to its original shape, and is capable of deforming many times without losing strength. Rubber

The rubber provides flexibility through its ability to move but return to its original position.

Steel
Using layers of steel with the rubber means the bearing can move in a horizontal direction but is stiff in a vertical direction

Damping Mechanism
1.Heavy damping mechanism incorporated in base isolation devices, is often considered a valuable source of suppressing vibrations thus enhancing building's Seismic performance. 2.Many buildings and bridges, both in New Zealand and elsewhere, are protected with lead dampers and lead and rubber bearings. 

CASE STUDY

Wellington Hospital
The new Wellington Hospital was completed in...
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