Five-degrees-of-freedom models that account for uplift, rocking, and sway of the foundation, in addition to horizontal and vertical deformation of the superstructure, were used to study the beneficial effect of foundation uplift to reduce the seismic damage to building structures. The elastic models accounted for geometric nonlinearity and expressed soil-and-foundation interaction as a function of contact area. The nonlinear models were subjected to a suite of ground motions. The results indicated that the vertical component of ground motions does not significantly affect the horizontal response of the superstructure and that the vertical response of the superstructure is produced primarily by foundation uplift.
