Figure 1 illustrates a structural problem which occurs in naval architecture, and which may also be of interest in the structural design of aircraft. Compressive loading is applied to one transverse edge of a stiffened flat sheet and reacted, not by equal compressive loads on the opposite transverse edge, but by shear forces along the two longitudinal edges. These shear forces, and the complementary shear forces acting on the transverse edges, arise from the connection of the stiffened sheet to adjacent structure. This situation arises, for example, at a ship's transverse bulkhead. The lower edge of the bulkhead is subjected to vertical loads applied by the ship's bottom structure, and these loads are transmitted upwards and outwards to the vertical edges of the bulkhead, thence to be diffused into the side shell plating.