Extreme event like an earthquake has taken the toll of millions of lives through the ages in the unrecorded, and recorded human history. The nature of forces induced is reckless, and lasts only for a short duration of time. Earthquake can cause havoc in case of high rise building, water tanks, nuclear power plants and many other strategically important constructions.
The traditional technique to provide safeguard the structures against damaging earthquakes is by strengthening, in which the size of different members is increased to resist more earthquake forces and dissipate the seismic energy. The alternative technique is base isolation by introducing the special devices between the base and foundation of the structure.In the event of an earthquake base-isolator tries to decouple the any structure from the damaging effect of ground motion.
One of the goals of base isolation is to lengthen the natural period of structure, which the aim of reducing the earthquake effect on superstructure. The other purpose of an isolation system is to provide an additional means of energy dissipation, thereby reducing the transmitted acceleration into the structure.
The base isolation system considered is elastomeric bearings consisting basic components as rubber and steel plates built through vulcanization process in alternate layers. These bearings are vertically stiff (to take care of high compressive load from superstructure) and isolation is achieved through horizontal flexibility and damping.
Economy of base-isolator can’t be seen only in terms of its initial cost but cost of repair and retrofitting on the building after occurrence of earthquake must be included. Introduction of base-isolation is simple and practical, and its concept is easy and clear for further expansion an application.