The Arc

The arch is important because of its structure. It's strong and sturdy. The curve also looks appealing, and it's compact. The arch is also easy to construct, and doesn't take too much time. The arch provides a structure which eliminates tensile stresses in spanning an open space. All the forces are resolved into compressive stresses, meaning that they're well balanced. Materials such as cast iron, stone, and concrete can resist compression, but are very weak when tension, or stress is applied to them. The arch is a very useful structure as it is completely self-supporting. This is due to the fact that all the compressive forces hold it together in a state of equilibrium. This also applies to surfaces without friction as well.