APPROXIMATION OF FREQUENCY RESPONSES BASED ON LARSSONS METHOD

This paper discusses the new aspects of the formulation for structural model updates presented by Larsson and Sas at the 10th International Modal Analysis Conference held in San Diego, California in February 19 91. First, a closed-form representation of the reduced impedance matri x is presented. It clarifies the issues associated with the range of t he excitation frequencies used in model updates. Second, the applicabl e range of excitation frequencies is considered through an example whe re low frequency local modes are present. Third, the computational asp ects of this algorithm are studied. It is shown that displacement sens itivity vectors corresponding to the virtual loads are critical in the computation of the reduced impedance matrix sensitivity. Finally, app licability of this algorithm for approximate frequency responses in st ructural optimization is studied. Numerical results are included to il lustrate the essence of this formulation.