Experimental Determination of Local Structural Stiffness by Disassembly of Measured Flexibility Matrices

[+] Author and Article Information
S. W. Doebling

Engineering Sciences and Applications Division, Engineering Analysis Group (ESA-EA), Los Alamos National Laboratory, M/S P946, Los Alamos, NM, 87545

L. D. Peterson

Center for Aerospace Structures and Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado 80309-0429

K. F. Alvin

Structural Dynamics and Vibration Control Dept., Sandia National Laboratories, M/S 0439, Albuquerque, NM, 87185-5800

J. Vib. Acoust 120(4), 949-957 (Oct 01, 1998) (9 pages) doi:10.1115/1.2893925 History: Received May 01, 1996; Revised August 01, 1997; Online February 26, 2008


A new method is presented for identifying the local stiffness of a structure from vibration test data. The method is based on a projection of the experimentally measured flexibility matrix onto the strain energy distribution in local elements or regional superelements. Using both a presumed connectivity and a presumed strain energy distribution pattern, the method forms a well-determined linear least squares problem for elemental stiffness matrix eigenvalues. These eigenvalues are directly proportional to the stiffnesses of individual elements or superelements, including the cross-sectional bending stiffnesses of beams, plates, and shells, for example. An important part of the methodology is the formulation of nodal degrees of freedom as functions of the measured sensor degrees of freedom to account for the location offsets which are present in physical sensor measurements. Numerical and experimental results are presented which show the application of the approach to example problems.

Copyright © 1998 by The American Society of Mechanical Engineers
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