BARREL ARCH
This shape is similar to the folded plate shell arch except that cross sectional elements are curved instead of being made with plane surfaces. The surface is more difficult to form but the widths of the individual elements may be made greater than for the folded plate shape. Arches of very long span are possible because the bending moments in an arch are much less than in a beam of comparable span.
Any number of different shapes may be used, such as the corrugated shape or the north ligh Lazy S shape. Lighting may be obtained by using skylights. The shearing forces are not very large in an arch so larger holes may be used than for a barrel shell.