Barrel shells in the form of corrugations may offer structural advantages and may have esthetic values which make such a roof desirable. Forms are not more difficult to build if the curvatures are not greater than the bending radius of the material used to line the forms. One structural advantage is that the same area is supplied at the top and bottom of the shells and they are suitable for continuous structures where the maximum area of concrete is required at the bottom of the shell at the support.
Instead of alternative concave and convex circles of the same radius, the curves may be alternate circles of long and short radius. For the mathematically inclined, the shape may be of the pure sine curve. There are innumerable combinations of curves, or curves and folded plates to serve the particular esthetic or structural function.