Isolating Buildings

1 -Introduction

Base Isolation systems reduce building vibrations during earthquakes. This means that the building distorts less, reducing the chance of damage.

Normally, a building is supported directly on its foundations, and it is said to have a fixed-base. When base isolation is used, special structural bearings are inserted between the bottom of the building and its foundation.

These bearings are not very stiff in the horizontal direction, so they reduce the fundamental frequency of vibration of a building. The frequency becomes so low that the building does not vibrate as strongly during an earthquake.

During an earthquake, a fixed-base building can sway from side to side. When a base isolation system is used, the sideways movement occurs mainly in the bearings, and the building hardly distorts at all.

There are many types of bearings used for base isolation. Here are two of them.

Isolating Buildings - 2 Rubber Bearings
Isolating Buildings - 3 Friction Pendulum Bearings


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from Bristol University