Types and Forms of Shell Structures

MULTIPLE BARRELS - OUTSIDE STIFFENERS

This structure shows a multiple barrel vault with vertical edge beams at the outside edges. The stiffeners have been place above the roof. The advantage of having the stiffeners on top is that there are no interruptions to the space inside the shell so both the inside appearance and the utility are better. Also, the movable formwork may be used which will slide with little decentering lengthwise of the shell.

A single span structure is shown here. Multiple spans should have an occasional expansion joint to reduce shrinkage and thermal stresses. This can be accomplished by cantilevering half the span from each adjacent stiffener. A small upturned rib is placed on each side of the joint and accordion type sheetmetal flashing is arranged to prevent roof leakage.

The maximum spans for this type shell are again limited by the geometry of the cross section. Assuming the maximum width of barrel to be 50 feet and maximum end slope to be 45 degrees, the rise would be about 14 feet; the maximum span would be in the order of 150 feet.