This document specifies the principles regarding the design of seismically isolated structures under earthquake effects.This document also describes the principles of construction management and maintenance, since proper construction management and maintenance are important for realizing high quality seismic isolation structures.This document is not applicable to bridges and LNG tanks, although some of the principles can be referred to for the seismic isolation of those structures.This document is not applicable to seismic isolation structures that reduce the vertical response to earthquake ground motions, since this document mainly specifies seismic isolation structures that attenuate the horizontal response to horizontal earthquake ground motions.This document is not a legally binding and enforceable code. It can be viewed as a source document that is utilized in the development of codes of practice by the competent authority responsible for issuing structural design regulations.NOTE This document has been prepared mainly for the seismically isolated structures which have the seismic isolation interface applied between a superstructure and a substructure to reduce the effect of the earthquake ground motion onto the superstructure. In most cases, the substructure refers to the foundation of the structure. However, the substructure in this document consists of a structural system below the isolation interface that has been designed with sufficient rigidity and strength. Examples include locating the isolation interface in a mid-storey of the building or above the bridge piers (see Annex E).