Slide 1

ARCHES AND ITS TYPES

A structure, usually curved, that when subjected to vertical loads cau-ses its two end supports to develop reactions with inwardly directed horizontal components. The commonest uses for an arch are as a bridge, supporting aroadway, railroad track, orfootpath, and as part of a building, where it provides a large open space unobstructedby columns.Anarchis a structure that spans a space while supporting weight. Arches appeared as early as the 2nd millennium BC in Mesopo-tamian brick architecture and their systematic use started with theAncient Romanswho werethe first to apply the techniqueto a wide range of structures.

The arch is significant because, in theory at least, it provides a structure which eliminatestensile stressesin spanning an open space. All the forces are resolved intocompressive stresses. This is useful because several of the available building materials such asstone,cast ironand concretecan strongly resist compression but are very weak when tension, shearortorsionalstress 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.

This is a general representation of the proport-ions and technical elements.1. Keystone 2. Voussoir3. Back 4. Impost5. Intrados 6. Rise7. Clear span, "Bay 8. Abutment

TYPES OF ARCHES

Round archor Semi-circular arch

Segmental archor arch that is less than a semicircleEquilateral pointed arch

Shouldered flat archThree-foiledcusped archHorseshoe arch9

Three-centered archElliptical arch

Inflexed archOgee archReverse ogee arch

Tudor archParabolicarch