CALCULATING THE DYNAMIC STIFFNESS MATRIX OF 2-D FOUNDATIONS BY DISCRETE WAVE-NUMBER INDIRECT BOUNDARY-ELEMENT METHODS

Apart from some special cases, calculating the dynamic stiffness matri x of foundations on a layered half-space, especially for embedded foun dations, is computationally expensive. An efficient method for two-dim ensional foundations in a horizontally layered soil media is presented in this paper. This method is based on indirect boundary element meth ods and uses discrete wave number solution methods for calculating Gre en's functions for displacements and analytical methods for the integr ations over the boundary. For surface foundations, the present method applies at all frequencies. For embedded foundations or for constructi ng energy transmitting boundaries, because the free-field part is mode lled by boundary elements and the excavated part is modelled by finite elements, the present method applies only at low frequencies for the spring coefficients (the real parts of the dynamic stiffness matrix) b ut applies at all frequencies for the damping coefficients (the imagin ary part of the dynamic stiffness matrix) for undamped sites. The nove lty of the method can be used for three-dimensional foundations.