PROCEDURE TO ACCOUNT FOR NON-LINEAR EFFECTS IN EMPIRICAL TRANSFER FUNCTIONS

摘要

A method to account for non-linear effects in the response of layered soil deposits is presented. This method is applied to modify the linear transfer function, in fact the amplitudes of the transfer function, called empirical transfer function. Actually, reductions and shifts to low frequencies present in the amplitudes of transfer functions under non linear conditions are regarded. These reductions and shifts are done separately. First,changes in both, shear waves velocity and material damping as a function of the peak ground acceleration in rock, are established. Then a spectral function of non linearity is computed. This function is the ratio between the inelastic transfer function, disregarding the shifts to low frequencies (increments in wave number), and the elastic one. The shifts in the frequency domain are explicitly introduced by means of a proper frequency scaling. The method is exact for homogeneous single layers. The method is done in seven steps described in the body of this work. Several results, as non linear transfer function, spectral ratios and synthetic seismograms are presented to show how easy and useful the method is.