In solving the problems of structural fluid dynamic interaction in the seismic response of such systems as dam reservoir and storage tank liquid, the classic added mass approach has been used extensively.
The classic added mass solution is accurate for fully submerged structures but gives only approximate results for partially submerged structures. This approximation is reported to apply particularly for higher modes of vibration.
In this paper the reason behind this approximation is explored and an accurate, modified, added mass approach is presented. The proposed approach is based on the results of dynamic tests in which the distribution and amount of added mass in pure modal vibration were measured.
Experimental findings, supported by theory, indicate that the modal added mass in partially submerged structures is essentially the same as the classic added mass for rigid vibration, but only a fraction of it participates in the vibration of higher modes. The modal participation factors are found to provide good measures for that fraction.
The accuracy of the proposed modified added mass approach is checked against the more elaborate Eulerian and Lagrangian solutions in a number of numerical examples including dam reservoir systems.
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