NON-STATIONARY ANALYSIS OF SOIL RIGIDITYAND DAMPING BY USE OF ARRAY STRONG-MOTION RECORDS

This paper deals with a method for analyzing the non-stationary variations of soil rigidity and damping using array strong-motion records. The concept of the “Complex Envelope” is used as a basic tool to analyze such non-stationary variations. The dynamic stress-strain relation of soils, which is usually available from array strong-motion records, is converted into an imaginary system by use of the “Complex Envelope” so that the rigidity modulus and damping ratio of soils are estimated in terms of time. The authors applied the method to the strong-motion records observed at Port Island during the 1995 Kobe Earthquake. This application confirms the validity and usefulness of the method.