Types and Forms of Shell Structures

GROINED VAULT - SQUARE IN PLAN

The groined vault is an intersection shell composed of four triangular pieces of cylindrical shells, arranged in a cross form so that there are arches on each of the sides. This is one of the most ancient of masonry arch structures and still used for underground water reservoirs of concrete without any reinforcing.

The usual vault is a continuous structure but only a single unit is shown here. The structure obtains its rigidity by the large angle between the shell components at the intersections which creates a very strong rib.

The size of these structures is almost unlimited because the form is inherently very strong and is stiffened by six complete arches. In order to take advantage of the rigs, it is necessary to have the center of the abutments at the center of the effective rib. Otherwise, an additional heavy rib is required which impairs the appearance of the groined vault.