Model updating - Endless possibilities

Finite element models are updated using test data to better represent the actual "as-built" characteristics of a system or prototype. Using commercially available software, a detailed finite element model can be easily updated to reflect the measured characteristics - whether they be frequencies, mode shapes or response functions. However, the accuracy of the updated model is heavily dependent on the location and type of discrepancy that exists and is strongly influenced by the analysts understanding of the model and selection of parameters that are used for the updating process. This paper uses simulated test data to show the sensitivity of the updated model to parameters selected in the updating process. The models presented are not intended to credit or discredit the approach but rather to provide a very unbiased view of the capabilities of the approach with its strengths and limitations. Models are intentionally developed that will span the full range of acceptable updated models to unacceptable ones. Different measured parameters are used (frequency, mode shape and response function differences) to perform the updating procedure to illustrate the improvement (and degradation) of the finite element model depending on the analysts proper (or improper) selection of parameters for change.