Earthquake Interaction for Multistory Building

The earthquake responses of multistory buildings are studied taking into account the soil-structure interaction effects. Fast Fourier transform techniques used to obtain the frequency-domain responses (transfer functions) and time-domain responses (time histories). The results show that the floor accelerations, distortions, and story shears are largest when the dominant frequency of an earthquake accelerogram matches the fundamental frequency of a building and the foundation soil is very stiff. Interaction caused by soil compliance generally reduces all these responses, however, rocking can become significant for heavy buildings founded on very soft soils, thus resulting in large total displacements. The maximum acceleration and story-shear responses within a building are, for practical purposes, independent of soil shear-wave velocities over 1000 fps if the dominant frequency of the earthquake is as high as the second-mode natural frequency of the structure.