Abstract:-Seismic isolation is a technology that decouples a building structure from thedamaging earthquake motion. It is a simple structural design approach tomitigate or reduce potential earthquake damage. In base-isolated structures,the seismic protection is obtained by shifting the natural period of thestructure away from the range of the frequencies for which the maximumamplification effects of the ground motion are expected; thus, the seismicinput energy is significantly reduced. At the same time, the reduction of thehigh deformations attained at the base of the structure is possible, thanks tothe energy dissipation caused by the damping and the hysteretic properties ofthese devices, further improving the reduction of responses of the structures.Base isolation is also an attractive retrofitting strategy to improve theseismic performance of existing bridges and monumental historic building.
Tominimize the transmission of potentially damaging earthquake ground motionsinto a structure is achieved by the introduction of flexibility at the base ofthe structure in the horizontal direction while at the same time introducingdamping elements to restrict the amplitude or extent of the motion caused bythe earthquake somewhat akin to shock absorbers. In recent years thisrelatively new technology has emerged as a practical and economic alternativeto conventional seismic strengthening. This concept has received increasingacademic and professional attention and is being applied to a wide range ofcivil engineering structures. To date there are several hundred buildings inJapan, New Zealand, United States, India which use seismic isolation principlesand technology for their seismic design.
Keywords— Seismic protection, Base isolation,Idealized behavior, Hysteresis loop, Ductility, Installation technique