Non-stationary Spectra Research Articles

Random Hydrodynamic Force on Dams from Earthquakes

A new solution for the hydrodynamic force on dams due to random earthquake accelerations is obtained in terms of nonstationary power spectra and mean square functions. Numerical results and special analytic solutions are obtained and presented in nondimensional forms. The earthquake acceleration is modeled by a stationary white noise with a unit step modulation function. The response spectra are narrowly banded and sharply peaked at resonant frequencies.

NON-STATIONARY SPECTRUM ANALYSIS OF OCEAN WAVES

Priestley's method [1, 2, 3] of non-stationary spectral analysis is extended to the case of digitally sampled records. A computation procedure previously proposed in an earlier work [4] is further investigated. This procedure compensates for the inherent difficulties in the theory and computes timedependent spectra from a sample in an iterative manner. Validities of the theory and the iterative procedure are tested with a simulated non-stationary process. Results establish a general agreement with theory, especially when spectra vary smoothly with time and frequency. Consequently, the procedure is applied to estimate non-stationary spectra for two wave records. A comparison is made between the non-stationary estimates and the stationary results derived from the same set of wave records.