The Effects of Radial Support Characteristics on Submarine Hull Instability Pressures

In practice, the submarine's major internal equipment is mounted to welded plating foundations, but submarine designers have been looking at the recent French innovation whereby the major internal equipment is mounted to a large truss/cradle structure through point supports. The focus of this research investigates the effects of radial point supports on the stability behavior of cylindrical shells under hydrostatic loading conditions . To investigate the stability phenomena of a point supported circular shells, the critical loads of point supported circular rings and cylinders were estimated numerically using an eigenvalue extraction routine. Next, shape imperfections were introduced to the geometry of the point supported cylinder, and this modified structure's buckling behavior was also estimated by eigenvalue extraction. To test the validity of using a linear numerical scheme, a nonlinear numerical scheme (RIKS Method) was used to predict the critical loads of the radially stiffened cylindrical shells, and the results were compared to the eigenvalue solutions. Furthermore, other important design parameters such as stresses, shell thickness, and shell weight were parameterized in evaluating the effectiveness of the point supports. Finally, an internal truss was attached to the submarine hull, and the effects of a this geometry on the buckling load were evaluated. The key findings of this research are the following: increasing the number of radial stiffeners dramatically improves the critical load of circular rings and cylinders, eigenvalue extraction was sufficient for predicting the buckling load in cylindrical shells, radial stiffener effectiveness drops as shell thickness increases for a constant radial stiffness value, and truss stiffness only plays a role in the stability behavior for low stiffness values of the radial supports. Technical Supervisor: James Gorman Thesis Supervisor : Dr. David Parks Professor, Mechanical Engineering