Seismic Interaction of Structures on Hysteretic Foundations

The effects of soil-structure interaction on the seismic response of simple structures are analyzed considering the foundation medium to behave as a linear viscoelastic solid. Two forms of viscoelastic action are investigated-the standard Voigt model and the constant hysteric model-and a procedure is recommended for interrelating the properties of the two models so that maximum deformation of the structure is approximately the same in the two cases. Comprehensive response spectra are presented for a range of the parameters defining the problem, and the results are used to access the accuracy of a simple approximate method of analysis in which the system is represented by a viscously damped simple oscillator. Simple expressions of high accuracy and numerical data are included for evaluating the characteristics of the replacement oscillator. It is shown that hysteretic action in the supporting medium may affect significantly the response of flexibly mounted structures.