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Variations in the dynamic properties of structures: the Wigner-Ville distribution

Bradford, Case and Yang, Jing and Heaton, Thomas (2006) Variations in the dynamic properties of structures: the Wigner-Ville distribution. , Pasadena, CA. (Unpublished)

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The Wigner-Ville Distribution (WVD) is a promising method for analyzing frequency variations in seismic signals, including those of interest for structural monitoring. Nonlinearities in the force displacement relationship will temporarily decrease the apparent natural frequencies of structures during strong to moderate excitation, and earthquake damage can permanently change building stiffnesses. A Fourier Transform of a building record contains information regarding frequency content, but it can not resolve the exact onset of changes in natural frequency – all temporal resolution is contained in the phase of the transform. The spectrogram is better able to resolve temporal evolution of frequency content, but has a trade-off in time resolution versus frequency resolution in accordance with the uncertainty principle. Time-frequency transformations such as the WVD allow for instantaneous frequency estimation at each data point, for a typical temporal resolution of fractions of a second. We develop a mathematical foundation for analyzing the evolution of frequency content in a signal, and apply these techniques to synthetic records from linear and nonlinear FEM analysis (including plastic rotation and weld fractures). Our analysis techniques are then applied to earthquake records from damaged buildings.

Item Type:Report or Paper (Technical Report)
Heaton, Thomas0000-0003-3363-2197
Additional Information:The authors thank the CSMIP program for the Imperial County Services Center records, Matt Muto (Caltech) for assistance with obtaining the Millikan Library / Whittier Narrows records, and Caltech Professor John Hall who developed the nonlinear FEM code used in our numerical simulations.
Group:Seismological Laboratory
Record Number:CaltechAUTHORS:20200518-124126273
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103278
Deposited By: Tony Diaz
Deposited On:18 May 2020 19:54
Last Modified:18 May 2020 19:54

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