Biaxial slip of a mass on a foundation subjected to earthquake motions

The relative motion of a rigid mass on a horizontal foundation undergoing biaxial random motion in the horizontal plane is studied under the assumption that Coulomb friction acts between the mass and the foundation. The displacement of the mass with respect to the foundation is a two-dimensional random walk whose statistical parameters depend nonlinearly on the intensity and correlation of the biaxial excitation. Analytical results are obtained via the Fokker-Planck equation and the equivalent linearization procedure and simulation results are obtained via the digital computer. These results may be useful for predicting the accumulated slip of a stiff compact structure free to slide on its foundation during an earthquake. (orig.)