Abstract:
Model
updating is an important issue in engineering. In fact a well-correlated model
provides for accurate evaluation of the structure loads and responses. The main
objectives of the study were to exploit available optimisation programs to create an
error localisation and
updating procedure of nite element models that minimises
the "error" between
experimental and analytical modal data, addressing in particular
the
updating of large scale nite element models with severe requirements on the
mode
shapes correlation.
A new
methodology and procedure that allows the semi-automatic adjustment of a
large nite element dynamic model of a structure to better represent the dynamic
characteristics of an actual structure was developed. The key aspect of the procedure
is a "two
steps" optimisation process to achieve a complete correlation of the modal
data.
Eigenfrequency deviations and mode shapes cross-othogonality (CO) and/or
modal assurance criterion (MAC) are used in the objective functions for the
estimation
problem of the updating parameters, that are the variables for tuning the
analytical model. Theoretical aspects and practical implementation conceming CO
and MAC, and their derivatives, have been fully developed and the advantages of
using these mode correlation indices in the objective function have been largely
commented.
The selection of the updating parameters is a complex issue and can be still
considered a
partially open point. In the new procedure the suggested automated
selection of the
updating parameters by means of a preliminary calculation of the
element modal strain energy and eigenvalue sensitivities is adequate for the
reduction of the
frequency deviations but could not be to improve the correlation
indices of the mode shapes.
The new
procedure was successfully applied four times: to a cantilever beam model,
the Garteur model, the Spacehab dynamic model and the Mini-Pressurised Logistics
Module model. The last application was a real life application on a large scale
structural mathematical model and in this case the procedure was mainly used for
error localisation
purposes. The developed procedure is robust, effective and
efficient, thus the original objectives of the study were largely met.
