Buckling Stresses of Stiffened Hyperboloidal Shells

Three hyperboloidal shell models made of epoxy resin (araldite) having nearly perfect geometry and constant wall thickness were tested first without stiffeners, afterwards with five, nine and 19 rings and 19 rings plus 36 meridional ribs. The axisymmetric loading resulting in various combinations of membrane stresses in ring and meridional directions was increased in steps until the first buckling wave could be observed. The initiation of the buckling process and the shifting of the region where the first buckling wave was observed were studied. The experimental results are compared with calculated values using a classical linear buckling theory. The experimental values fitted a nondimensional empirical law in terms of the uniaxial buckling stresses for each type of stiffening. An approach, based on the theoretical results and the tests carried out, is proposed to describe the buckling behavior of hyperbolic shells of revolution with and without stiffeners.