MODELLING OF SOIL-STRUCTURE INTERACTION BY FINITE AND INFINITE ELEMENTS

• Main Author: MEDINA-MELO, FRANCISCO JORGE
• Format: Dissertation
• Language: English
• Subjects: engineering, civil

A direct method for solving dynamically excited structures on elastic semi-infinite media is suggested as an improvement over available approaches. The method consists in modelling 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 cylindrically orthotropic, elastic, unbounded continua. The element is capable of propagating Rayleigh, shear and compressional waves 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 of a rigid circular plate subjected to harmonic loading on semi-infinite media. By using the finite 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.