Efficient modal dynamic analysis of flexible beam-fluid systems

This paper proposes an efficient simplified method to determine the modal dynamic and earthquake response of coupled flexible beam-fluid systems and to evaluate their natural vibration frequencies. The methodology developed extends available analytical solutions for mode shapes and natural vibration frequencies of slender beams with various boundary conditions to include the effects of fluid-structure interaction. The proposed method is developed for various beam boundary conditions considering lateral interaction with one or two semi-infinite fluid domains. Numerical examples are provided to illustrate the application of the proposed method, and the obtained results confirm the importance of accounting for fluid-structure interaction effects. We show that the developed procedure yields excellent results when compared to more advanced coupled fluid-structure finite element solutions, independently of the number of included modes, beam boundary conditions, and number of interacting fluid domains. The proposed simplified method can be easily implemented in day-to-day engineering practice, as it constitutes an efficient alternative solution considering the fluid-structure modeling complexities and related high expertise generally involved when using advanced finite elements.