Combinations of positive and negative double curvature shells turn out to be especially interesting. The former may be both of square and rectangular plan, added near standing structures are of rectangular or triangular plan. High-technological, light-weight, reliable and economical structures, constructed of spatial frames, spatial trusses, rib and cable nets, folded plates and double- curvature shells with different Gaussian curvature and geometry, have been investigated.

The modified design method based on the Heinrich Laul's approximation method of shear forces was used. The increase of membrane shear was calculated using the equilibrium of unit strips, continuity of deformations, and the conditions of the minimum of potential energy (Castigliano-Ritz method). The method takes into account the influence of cracks in reinforced concrete shells, the location of the reinforcement, its shape, curvature and prestressing, different variants of the ribs, openings and edge elements, and physical and geometrical nonlinearity. To enable to study space structures with real edge conditions and additional influences from supporting elements fiberglass plastic geometrical scale models have been made and tested.

The shells were examined both in an elastic and cracked state with real boundary conditions.

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