Modal Parameter Estimation for Jacket-Type Platforms Using Free-Vibration Data
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 137, Issue 5
Abstract
An accurate estimation of the modal parameters of a structure, including modal frequency and damping ratio, is crucial for many practical engineering problems. This article introduces Prony’s method for identifying multiple modal parameters of a jacket-type platform from the measured free-vibration data. In contrast to the Fourier analysis for the decomposition of a periodic signal, Prony’s method involves the decomposition of a transient signal into a number of damped sinusoidal components. By using a finite-element model of a realistic offshore jacket-type platform, free-vibration data, corresponding to two different initial displacement patterns, were extracted and used in a numerical study. From the sampled response acceleration signals associated with each of the initial displacement patterns, the modal parameters of different participating modes were accurately determined. This numerical study demonstrates that the modal parameters, of at least the first nine modes of the jacket-type platform, including six translation modes and three torsion modes, can be accurately estimated by using the proposed method.
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© 2011 American Society of Civil Engineers.
History
Received: Apr 16, 2010
Accepted: Feb 9, 2011
Published online: Feb 11, 2011
Published in print: Sep 1, 2011
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