Structure-Ground Interaction in Earthquakes

A method of analysis is presented for determining elastic structure-ground interaction effects of single-story structures under earthquake loads. The method derives an equivalent SDF model for the relative story displacement, incorporating the effects of horizontal and rotational base flexibility in a structure. The equivalent SDF model then permits the determination of the seismic interaction response directly from established or assumed response spectra, or from response calculations of ordinary SDF systems. Sample calculations are presented showing responses for the interaction system, the equivalent SDF model, and a SDF system with the same natural frequency as the interaction structure. A study of a wide range of parameters under earthquake-type disturbances establishes that, for the interaction systems considered, interstory displacements are reduced in relation to a SDF system with identical fundamental frequency and interstory damping.