AN ANALYSIS OF FREE VIBRATION OF ORTHOGONALLY STIFFENED CYLINDRICAL SHELLS WITH STIFFENERS TRETED AS DISCRETE ELEMENTS

A free vibration analysis is developed for a ring-and-stringer-stiffened circular cylindrical shell with various types of end conditions and with the stiffeners treated as discrete elements. The number and spacing of stiffeners are arbitrary, so that there is no limitation due to averaging stiffener effects over the shell surface. The analysis shows that stringers considered as discrete elements couple circumferential modes of different wave numbers and also couple symmetric and antisymmetric circumferential modes. Moreover, the natural frequencies associated with the symmetric and antisymmetric modes may have different values, indicating the existence of “double resonances.” Numerical results show that even stringers that are comparatively weak in bending may have a significant effect on both the modes of vibration and differences between the symmetric and antisymmetric frequencies. © 1968 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.