Response variability for a structure with soil-structure interactions and uncertain soil properties

A non-classical modal analysis based formulation is used to quantify the ef fect of uncertain soil-foundation properties on structural response in seis mically excited soil-structure interacting (SSI) systems. This formulation allows the response of the interacting system to be represented as a superp osition of the responses of uncoupled modal equations which include an addi tional random vector to represent the system uncertainties. The method is i mplemented by an effective Gaussian quadrature integration method to find t he frequency-domain stochastic response properties of the SSI systems. Nume rical examples of MDOF SSI systems illustrate that the main effect of uncer tain soil properties on such SSI systems is to alter the magnitudes of moda l response near the system resonant frequencies, rather than to shift the r esonant frequencies. When the uncertainty of soil foundation properties is not negligible, there may be significant variations of the transfer functio ns for modal response and significant uncertainty about the spectral densit y of structural response may occur near the system's resonant frequencies. (C) 2000 Elsevier Science Ltd. All rights reserved.