What is an Arch?
An arch is a structure that spans a space and supports structure and weight above it.
Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.
What are the Types of Arches?
Arches have many forms, but all fall into three basic categories: Circular, pointed, and parabolic.
Arches with a circular form, also referred to as rounded arch, were commonly employed by the builders of ancient history, heavy masonry arches.
Ancient Roman builders relied heavily on the rounded arch to span large, open areas.
Several rounded arches placed in-line, end-to-end, form an arcade, such as the Roman aqueduct.
Pointed arches were most often used by builders of Gothic-style architecture.
The advantage to using a pointed arch, rather than a circular arch, is that the arch action in a pointed arch produces less thrust at the base.
This innovation allowed for taller and more closely spaced openings, typical of Gothic architecture
Vaults are essentially "adjacent arches [that] are assembled side by side."
If vaults intersect, complex forms are produced with the intersections.
The forms, along with the "strongly expressed ribs at the vault intersections, were dominant architectural features of Gothic cathedrals."
The parabolic arch employs the principle that when weight is uniformly applied to an arch, the internal compression resulting from that weight will follow a parabolic profile.
Of any arch type, the parabolic arch produces the most thrust at the base, but can span the largest areas.
It is commonly used in bridge design, where long spans are needed.