In analyzing the behavior of a structure/system, the low frequency response can be readily determined using deterministic approaches. The high frequency behavior can be estimated using statistical based solutions, most common of which being SEA. In between the high and low frequencies, there is a region - the mid-frequency region for a lack of a better description, - where the response of the structure is very much controlled by the structure modal behavior, and slight variations in the physical characteristics and parameters of the structure can create significant differences in the response. General statistical approaches, such as SEA, do not capture the modal behavior and therefore will not closely represent the behavior of the structure. Therefore an approach based on deterministic methods with the introduction of statistical variations is required. The question is to how efficiently introduce the statistical variations. Using an approach developed by Mace and Shorter, based on the component mode synthesis (CMS) method and the perturbation of modes, an analysis is performed of a T-beam structure for which response results are available in the literature. CMS based results using perturbations of the structure physical characteristics or the modes are computed and compared to the available results.
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