The Earthquake Engineering Online Archive

Earthquake analysis of multistory buildings including foundation interaction

Chopra, Anil K.; Gutierrez, Jorge A.

UCB/EERC-73/13, Earthquake Engineering Research Center, University of California, Berkeley, 1973-06, 41 pages (535/C49/1973)

Efficient methods for dynamic analysis of response of multistory buildings including foundation interaction to earthquake ground motion are presented. The system considered is a shear building on a rigid circular disk footing attached to the surface of a linearly elastic half-space. In the first method, structural displacements are transformed to normal modes of vibration of the building on a rigid foundation. The analysis procedure is developed and numerical results are presented to demonstrate that excellent results can be obtained by considering only the first few modes of vibration. The second method developed is based on the Ritz concept. The structural displacements including those at the base are expressed as a linear combination of Ritz vectors, which are selected as the first few modes of an associated building-foundation system. Numerical results are presented to demonstrate the effectiveness of this approach. As the number of unknowns are reduced by transforming to generalized coordinates, both methods are much more efficient than direct methods; between the two methods, the former, based on transformation to normal modes of the building on a rigid foundation, is preferable.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-73-13.pdf (1 MB)