Abstract: A fiber reinforced shell structure of synthetic material has an outer skin supported on a skeleton of longitudinal stringers interconnected by ribs. The stringers have a channel cross-section filled with a hard foam. The ribs have an approximately [ or I-shaped cross-section. The ribs are formed by an outer chord and by an inner chord interconnected by a web. If the structure is cylindrical, for example, the ribs extend circumferentially. The rib webs are made of rib web segments which are displaced relative to each other, for example in the circumferential direction in case of a cylindrical structure. The displacement of the web elements corresponds to the on-center spacing between neighboring longitudinal stringers, whereby the fiber reinforced material of the end portions of the rib web segments merge into rib reinforcing or bracing members, where the ribs intersect the stringers. The rib bracing members alternate in opposite directions along a rib and are filled with a hard foam.