Free Vibration Analysis of Plates with Arbitrarily Oriented Branched Stiffeners

Background In the present work, undamped free vibration responses are numerically explored on stiffened rectangular plates following a novel stiffener designing concept where arbitrarily orientated stiffeners are branched out from a central longitudinal stiffener. Purpose The correlating frequencies with corresponding orthogonally traditional stiffened plates are simultaneously compared. The stiffened plates with arbitrarily oriented branching and their orthogonal counterparts are analyzed numerically by the finite element methodology employing an efficient software package ANSYS. Methods The plates and stiffeners of all the stiffened plates are modeled as the 2-D geometries and discretized considering quadratic shell elements. The block Lanczos eigenvalue extraction algorithm has been employed through ANSYS to obtain the undamped natural frequencies and corresponding mode shapes. Investigations on parameters controlling stem lengths and the placements and orientations of the branch stiffeners are explored. Simultaneous comparison with orthogonal stiffener arrangements evaluated for identical stiffener depth is conducted. Results Higher and lower magnitudes of correlating characteristic frequencies, such as the fundamental frequencies, are obtained considering simple alterations in the branching parameters. However, heavier stiffeners with increased thickness are required for traditional orthogonally stiffened plates, especially to yield higher fundamental frequencies. Such observations remain valid for different plate aspect ratios also. Conclusion The geometric anisotropy of the branched layouts causes such modification of the overall stiffness distributions of the stiffened plates. Thus, the newly proposed branched layouts efficiently alter the dynamic responses at reduced mass allocations compared to the orthogonal arrangements.