224 Romuald Tarczewski Post-tensioning cables are always placed at the internal side of curved shell.In case of anticlastic shells,cables are placed in two layers -at the opposite sides of the shell.Direction of cables in each layer corresponds with the curvature of the shell,Fig.6.The cables can be placed directly below the cushions or below cross-braces.In both cases the cable should be able to slide freely through the nodes.Both,fiber ropes (made of natural or man-made fibers)and wire ropes can be used as post-tensioning cables.It is significant that the cushion was protected from damages caused by ropes,e.g.by means of protective jackets. 2.3 Transmission of Forces After completion,modular elements must transmit internal forces induced in the structure.It is possible due to the compression of cushions'sides(touching each other)and tension of their external cover and post-tensioning cables, Fig.3.Thus,the way of assembling the cushions must ensure a full contact of side surfaces and continuity of external cover. These basic principles allow setting a geometrical configuration of the shells of various size and shape,designed for various purposes. tension of external cover compression of side surfaces air-inflated cushion post-tensioning tension of cable bottom cable cross-braces Fig.3.Transmission of forces in modular air-inflated shells224 Romuald Tarczewski Post-tensioning cables are always placed at the internal side of curved shell. In case of anticlastic shells, cables are placed in two layers – at the opposite sides of the shell. Direction of cables in each layer corresponds with the curvature of the shell, Fig. 6. The cables can be placed directly below the cushions or below cross-braces. In both cases the cable should be able to slide freely through the nodes. Both, fiber ropes (made of natural or man-made fibers) and wire ropes can be used as post-tensioning cables. It is significant that the cushion was protected from damages caused by ropes, e.g. by means of protective jackets. 2.3 Transmission of Forces After completion, modular elements must transmit internal forces induced in the structure. It is possible due to the compression of cushions’ sides (touching each other) and tension of their external cover and post-tensioning cables, Fig. 3. Thus, the way of assembling the cushions must ensure a full contact of side surfaces and continuity of external cover. These basic principles allow setting a geometrical configuration of the shells of various size and shape, designed for various purposes. Fig. 3. Transmission of forces in modular air-inflated shells