Strong earthquakes’could Induce targe overturning mo.,.,.ntl cluling the ba.e mati of thft structur •• to temporarily 11ft off the ground durl”o lome cycles and results in non-linear Interactive forc.s between the ba •• of structure and the foundation. This study Incorporates the analyals of. box type cyllndrlca’ Itruet””I’ Iyatem to evah.ate the Importance of non-Un .. , loll-structur. Interaction. A parametric Itudy Involving vlrloua atructUNII and foundation propertl •• ha. be.n carried out Incorporating both linear and non-line.r b.havlour of the foundation contact arta. The .ffect of modal damping ” studied and the Influenca of various assumptions has been broughl oul, III. concludod Ihal d.mplng .alu .. for Ihe slruclur .. found.d on 8ofl.r .011. conllderably Influlnca … pon •• and Ihtrel.or. .bould b. ca .. fully .elected, Non·llne.r a.alyel. Inc,rporillng oll.cl of ,’pplng .hould be carried out for Important structure. foundecf on loftlr IOU., though for atlH,r foundatfona IIn.ar analysl, may be ,atlsfactory.