The Minimum Weight Design of Tank Structures

This paper defines the geometry of minimum weight tank structures of given enclosed volume. A tank structure is considered to comprise a circular cylindrical shell (monocoque or stiffened), bulkheads, and skirt structures. The analyses, starting from established criteria of failure, apply to the loading cases of longitudinal compression and bending moments in combination with internal pressure. The bulkhead geometries are flat, hemispherical, and ellipsoidal. For monocoque shells, the analyses yield the radius and wall thicknesses prescribing a minimum total weight of cylindrical tank wall, bulkheads, and skirts (unpressurized cylindrical appendages, for example, interstage structure). For stiffened shells, the analyses yield the tank radius, skin gauge, stringer spacing, and frame spacing prescribing a minimum total tank weight. An optimum relative geometry is defined for three types of stringers.