Seismic Rotations and Rotational Seismic Input for Building Design

Abstract

The rotational seismic inputs for building design were discussed. The free ground rotations and the relation between free ground rotations and basement rotations were derived. The results show that the relation depends on the basement size, site and seismic frequency. For most building, the differences between the free ground rotations and the basement rotations are small. The suggestion is that for tall buildings the free ground rotations can be taken as the seismic input, but for low-rise building with large basement, the response spectra in short period region should be reduced.