Page "Arch" Paragraph 2

The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning a great amount of open space.

All the forces are resolved into compressive stresses.

This is useful because several of the available building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them.

By using the arch configuration, significant spans can be achieved.

This is because all the compressive forces hold it together in a state of equilibrium.

This even applies to frictionless surfaces.

However, one downside is that an arch pushes outward at the base, and this needs to be restrained in some way, either with heavy sides and friction or angled cuts into bedrock or similar.