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Generalized Modal Identification of Linear and Nonlinear Dynamic Systems


Peng, Chia-Yen (1988) Generalized Modal Identification of Linear and Nonlinear Dynamic Systems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/e70y-gz66.


This dissertation is concerned with the problem of determining the dynamic characteristics of complicated engineering systems and structures from the measurements made during dynamic tests or natural excitations. Particular attention is given to the identification and modeling of the behavior of structural dynamic systems in the nonlinear hysteretic response regime. Once a model for the system has been identified, it is intended to use this model to assess the condition of the system and to predict the response to future excitations.

A new identification methodology based upon a generalization of the method of modal identification for multi-degree-of-freedom dynaimcal systems subjected to base motion is developed. The situation considered herein is that in which only the base input and the response of a small number of degrees-of-freedom of the system are measured. In this method, called the generalized modal identification method, the response is separated into "modes" which are analogous to those of a linear system. Both parametric and nonparametric models can be employed to extract the unknown nature, hysteretic or nonhysteretic, of the generalized restoring force for each mode.

In this study, a simple four-term nonparametric model is used first to provide a nonhysteretic estimate of the nonlinear stiffness and energy dissipation behavior. To extract the hysteretic nature of nonlinear systems, a two-parameter distributed element model is then employed. This model exploits the results of the nonparametric identification as an initial estimate for the model parameters. This approach greatly improves the convergence of the subsequent optimization process.

The capability of the new method is verified using simulated response data from a three-degree-of-freedom system. The new method is also applied to the analysis of response data obtained from the U.S.-Japan cooperative pseudo-dynamic test of a full-scale six-story steel-frame structure.

The new system identification method described has been found to be both accurate and computationally efficient. It is believed that it will provide a useful tool for the analysis of structural response data.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Mechanics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Mechanics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Iwan, Wilfred D.
Group:Earthquake Engineering Research Laboratory
Thesis Committee:
  • Iwan, Wilfred D. (chair)
  • Jennings, Paul C.
  • Beck, James L.
  • Hall, John F.
  • Knowles, James K.
Defense Date:1 September 1987
Other Numbering System:
Other Numbering System NameOther Numbering System ID
EERL Report87-05
Funding AgencyGrant Number
Record Number:CaltechTHESIS:03132013-163747278
Persistent URL:
Related URLs:
URLURL TypeDescription ItemTechnical Report EERL 87-05 in CaltechAUTHORS
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7516
Deposited By: Benjamin Perez
Deposited On:14 Mar 2013 15:14
Last Modified:23 Aug 2021 23:36

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