Components of the arch

COMPONENTS OF THE ARCH STRUCTURE

The main structural components of the arches are

1.     Abutments: These are the structures are at the edges of the arch on which arch rests. They are also termed as supports, which are used to resist lateral loads due to arch action.

2.     Crown: Crown is the point on the Arch with highest elevation. It is also termed as voussoirs. The main function of crown is that it takes up the external load (in downward direction) on it and coverts the load into lateral force or thrust, which is transmitted to the supports and finally to the ground.

3.  Springing: The connecting junction between the Arch rib and the Abutment is called as springing.

4.   Span of arch: the clear horizontal distance between two supports of an arch is called as span of the arch. Generally, span of arch in case of tied arches carrying highway will be in the range 75m to 250m. In case of railways, the span range would be 50m to 200m.

5.     Rise: The perpendicular distance between the line of action of the support and the crown point of the arch. The height of rise in an arch as in case of parabolic arch subjected to entire udl is generally opted as 1/3 of span. If the arch is subjected to the unsymmetrical loading, then height of rise in the parabolic arch is generally taken as 1/5 to 1/6 of the span. (Ref: Lipson & Haque ,ASCE ,1980).