A SIMPLIFIED PROCEDURE FOR TORSIONAL IMPEDANCE FUNCTIONS OF EMBEDDED FOUNDATIONS IN A SOIL LAYER

A simplified calculation procedure for torsional impedance functions o f circular embedded foundations in a soil layer with rigid base is pre sented The solution is constructed by means of linear combinations of natural modes of propagation and participation factors. The unknown co efficients of such expansions are obtained from the continuous treatme nt of appropriate boundary conditions in the least-squares sense. The influence of soil material damping is investigated by using hysteretic and viscous models. Dynamic stiffnesses of soil-foundation systems av e computed for different foundation embedments and soil layer depths, Finally, the practical importance of introducing viscous instead of hy steretic damping in linear interaction analyses in the time domain is discussed. Copyright (C) 1996 Elsevier Science Ltd.