Modal analysis for the global flexural response of ships

Abstract Modal Analysis is a powerful procedure to obtain dominant vibration modes in structures from measurements of the structural response only. This paper revises the theoretical framework for application of the modal analysis. Traditionally, modal analysis is applied using acceleration measurements to obtain the shapes, frequencies and structural damping of the flexural vibration modes. With some modifications the procedures can also be applied to strain measurements and both types of data combined. Operational Modal Analysis has been applied to multiple sets of in-service measurements on ship structures. Procedures have been developed to execute the modal analysis fully automatically over large batches of data. These procedures include convergence checks and mode shape identification. This enabled the authors to monitor changes in the modal characteristics of the structure over time.

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