Stochastic approach for determination of stationary duration of strong ground motion

Abstract

Strong motion duration is important parameter for nonlinear behaviour of structures and foundation soils. The estimates of duration of future earthquake shaking together with the knowledge of intensity of such shaking are essential tools in the hands of a design engineer. The definition of duration, as used by different investigators, has evolved with time from simple “bracketed” definitions to frequency dependent functional. In this paper, the frequency-dependent duration is defined via stochastic response analysis of SDOF structures. The present definition of duration combined with information about Fourier spectral amplitudes at all frequencies will provide most of the parameters of the strong ground motion, necessary for analysis of response of structures and soils to earthquake excitation. The stationary duration proposed here has been defined in such a way that it represents the duration of an equivalent stationary response of SDOF systems with specified natural periods and damping ratios. Acceleration time histories of major earthquakes in India are used to illustrate the estimation of the proposed duration.