Types and Forms of Shell Structures

GROINED VAULT - POLYGONAL PLAN

This structure is similar to the previous groined vault, square in plan, except that there are five triangular cylindrical elements instead of four. The shells which form the dome all have axes perpendicular to the vertical axis. Again, an excellent structural rib is formed by the intersection.

Arched stiffening ribs are required around the outside of the structure and these ribs exert thrusts at their abutments. Therefore, either a steel tie is required at this level (it can be hidden by the window), or if the area must be open, thrust abutments can be used. There are, of course, many possible variations on the structure sketched here. If six sides are used, a continuous series of shells my be constructed and units of this type could alternate with those having a shallow intersection.