#1700 ... Isolation

Doesn't look much but in a place like Wellington ... with many earthquake fault lines running through the landscape ... these seismic isolators are are more common in the construction of significant buildings. These are in the new Wellington Hospital building ... Te Papa has them as well.

How do base isolators work?
Base isolation is a technique developed to prevent or minimise damage to buildings during an earthquake. It has been used in New Zealand, as well as in India, Japan, Italy and the USA. A fixed base building (built directly on the ground) will move with an earthquake’s motion and can sustain extensive damage as a result.

When a building is built away (isolated) from the ground, resting on flexible bearings or pads known as base isolators, it will only move a little or not at all during an earthquake. The isolators work in a similar way to car suspension, which allows a car to travel over rough ground without the occupants of the car getting thrown around.

Base isolation technology can make medium-rise masonry (stone or brick) or reinforced concrete structures capable of withstanding earthquakes, protecting them and their occupants from major damage or injury. It is not suitable for all types of structures and is designed for hard soil, not soft.

One of the original base isolated structures – the William Clayton building in Wellington – uses about 80 lead rubber bearings, but this number depends on how engineers want to distribute the load.