SEISMIC BASE ISOLATION
A limited earthquake safety can be achieved by means of conventional design techniques. Structures do not collapse and can satisfy “life safety”, but this performance is not enough for strategically important structures. Structures such as hospitals, airport terminals, viaducts, critical production and storage facilities are needed to remain functional even just after strong earthquakes. Currently, base isolation application is the most effective way to satisfy this. Base isolation is the only way to reduce floor accelerations and interstory drifts in the structures at the same time. By minimizing floor accelerations and intestory drifts, it is not only possible to reduce damage on nonstructural components, but also protect sensitive machine and equipment in the structures. This allows, along with the protection of load carrying structural elements, the building to remain fully functional after earthquakes.
Base isolation is applied by means of base isolation devices (seismic isolators) replaced underneath structures, and create an isolation interface. Impact of ground shaking is aimed to be reduced by this interface to protect the structure above. In other words, structure above is separated from the ground, where earthquake hits; and therefore, protected from the destructive effects of earthquakes.
The most important property of base isolation interface is increasing the period of structures from 0.1-1.0 seconds, which is the region where high accelerations are imposed to the system, to 2.0-3.0 seconds range. Additionally, because of the nature of base isolation devices, higher damping values are achieved. Increased displacement demand caused by the shifting period is also carried by the base isolation devices, which allow the superstructure to move as a rigid body.