Dynamic Property Identification of Soil Used in Shaking Table Test: A Comparison of Several Methods

Abstract eng:
Fundamental frequency and damping ratio of soil are very important parameters for calculating dynamic responses of underground structures subject to earthquake excitation. In current practice, these dynamic properties are determined either by static experiment or identification based on spectral analysis. The static experiment, however, may not reflect the evolution of soil properties with the vibration amplitude and frequency. Therefore, the viscous damping ratio of silty clay and its frequency used in a series shaking table test are determined in this paper by three commonly used techniques, i.e. the stochastic subspace identification (SSI), frequency domain decomposition (FDD) and empirical mode decomposition (EMD) plus Hilbert transform (HT). Following items are discussed in details: (1) changing characteristics of soil subjected to different excitation types and with different depth (2) selection of calculating parameters in HHT method (3) discrepancies of results identified by the three methods; also the paper explores the suspending problems in dealing with the large damping ratio systems, willing to propose a new definition method of soil damping in terms of elastic and plastic deformation.

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