Pure Arch and Shell


The classic simplicity of this structure may be used with startling effect. There are only two structural elements and these are clearly expressed so that their function is evident. Obviously, if the shells are obscured by the walls necessary to enclose this space, much of the effect is lost. However, window walls would be in keeping with the spirit of the design and can be made to follow the curve of the arch.

If this structure is to be used as a canopy, the obvious curve of the arch is a ellipse because the arches can spring almost vertically from the ground and the slanting member will not be as great a hazard to people's heads. The curve requiring the least material would be the thrust line, or funicular curve, for the loads on the structure. This form would have considerable curvature at the top but would be practically straight from the edge of the shell to the ground. The larger the arch span, the greater the saving of concrete and reinforcing by the use of a funicular curve.