The Earthquake Engineering Online Archive

Modelling of soil-structure interaction by finite and infinite elements

Medina, Francisco

UCB/EERC-80/43, Earthquake Engineering Research Center, University of California, Berkeley, 1980-12, 64 pages (535/M35/1980)

A direct method for solving dynamically excited structures resting on elastic, semi-infinite media is suggested as an improvement over available approaches. The method consists of modeling the near-field with finite elements and the far-field with infinite elements. The method falls within the framework of the classical finite element method and preserves its flexibilities. The key to the success of the proposed method is the proper definition of the infinite element shape functions. The requirements that these shape functions must fulfill are clearly outlined. An axisymmetric infinite element is developed to solve three-dimensional wave propagation problems in cylindrical, orthotropic, elastic, unbounded continua. The element is capable of taking into account Rayleigh, shear, and compressional wave propagation in the frequency domain. A scheme to numerically integrate the element characteristic matrices is formulated based upon Gauss-Laguerre quadrature. The method is successfully applied to find the compliance functions for a rigid circular plate subjected to harmonic loading and resting on semi-infinite media. By using the infinite elements, the size of the near-field may be kept small. Consequently, the system is characterized by relatively few degrees-of-freedom, thus providing the analyst with an inexpensive solution.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-80-43.pdf (1 MB)