Earthquake Isolation of Multistory Concrete Structures.

A new concept is introduced for the protection of multistory concrete structures from the effects of earthquake ground motions. The concept is known as an isolation technique in that the super-structure is effectively insulated from the ground vibrations. Conventional concrete frame superstructures must dissipate the energy of a major earthquake by distorting inelastically. The isolated super-structure can be made to remain elastic throughout a major earthquake because the isolation devices concentrate this energy dissipation at the base of the structure. Safety is further enhanced because the isolation devices support no part of the verti-cal gravity load of the superstructure. The results of tests on a mathematical model of an isolated multi-story structure are presented. Such tests show that isolation techniques can re-duce the maximum base shear to a level below that causing initial yield of the superstructure, and that this shear force can be reliably established in design [ABSTRACT FROM AUTHOR]