Arch shapes are capable of supporting large loads, as weight and thrust are evenly distributed downwards from the top of the arch. In masonry arches, the keystone at the top and centre of the arch locks the other elements into place, held by the compression they exert against one another.
A vault is an arched shape used to form a structure such as a roof or ceiling. A barrel vault is a continuous arched shape. It may be cylindrical in form, resembling the roof or a tunnel, or may be pointed at its apex. It may be formed when arches or vaults are placed side by side, or as a continuous shell.
Barrel vaults are first thought to have been developed by the by the Sumerians, and were subsequently used by the Egyptians. They were used extensively in Ancient Rome for stone structures such as cisterns and aqueducts and as part of major buildings such as the Colosseum. Throughout the Middle Ages they were used across Europe as part of the construction of churches, and they continue to be a feature of modern architecture and engineering.
Barrel vaults must be able to withstand the outward pressure on the lower parts of the vault imposed by the structure above. If the barrel vault is underground, the pressure might be resisted by the ‘fill’ surrounding it. If it is above ground, the outward pressure can be resisted by thick supporting walls, although this becomes less practicable as the size of the vault increases. Additional strength can be provided in the form of supporting columns, stiffening diaphragm beams, side anchors or parallel walls that can distribute stress.
A groin vault (double barrel vault or cross vault) is formed by the intersection of two barrel vaults at right angles. The ‘groin’ is the edge between the intersecting vaults. This is a more efficient structure that only has to be restrained at its corners. A series of groin vaults can be built next to one another to create a similar effect to a simple barrel vault.
Stepped barrel vaults are formed by a series of barrel vaults at different levels.
 Related articles on Designing Buildings Wiki
- Bridge construction.
- Bridges of the world.
- Conoid shell.
- Domestic roofs.
- Elements of classical columns.
- Folded plate construction.
- Flying buttress.
- Hyperbolic paraboloid.
- Long span roof.
- Pendentive dome.
- Portal frame.
- Shell roof.
- Suspended ceiling.
- Tunnels of the world.
- Types of ceiling.
- Types of dome.
- Wall types.
 External references
- ‘Building Construction Handbook’ (6th ed.), CHUDLEY, R., GREENO, R., Butterworth-Heinemann (2007)
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