The Earthquake Engineering Online Archive

Dynamic behavior of ground for seismic analysis of lifeline systems

Sato, Tadanobu; Der Kiureghian, Armen

UCB/EERC-82/01, Earthquake Engineering Research Center, University of California, Berkeley, 1982-01, 75 pages (390/S28/1982)

A new mathematical formula is derived for the general wave transfer function in multilayered media with inhomogeneous and nonlinear soil properties. It is assumed that the ground consists of horizontally stratified layers overlying a homogeneous halfspace which is excited by vertically incident, plane shear waves. To formulate the nonlinear harmonic wave solution, the surface layer is regarded as a multilayered system consisting of infinite numbers of sub-layers with infinitesimal thicknesses. The modal superposition procedure based on the response spectrum approach provides an expedient tool for dynamic analysis of surficial ground. The characteristic equation for obtaining natural frequencies and free vibration modes is derived by using the proposed wave transfer function. Previously, modal analysis had been used only for linear systems. To make the modal analysis method applicable to nonlinear systems, a repetition scheme is proposed for calculating the modal stiffness and damping. The scheme is an adaptation of the equivalent linearization technique. The estimation of intensity of ground shaking is based on a response spectrum for stationary random vibration analysis. The results determined from this research, in conjunction with fatigue theory, are used to study the liquefaction problem in soil layers with general topography. Application of the proposed methods for use in the assessment of the seismic reliability of lifeline systems is discussed.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-82-01.pdf (4 MB)