Relation between the radius Simple circular curve Relation between the radius and Degree of a curve

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SURVEYING 2130601

Simple circular curve Elements of a simple circular curve Back tangent: the tangents line before the beginning of the curve is called the back tangents or the rear tangents. The line AT is the back tangent. Forward tangents: the tangents line after the end of the curve is called the forward. The line T2B is the forward tangent. Point of intersection: the point I where the back tangents when produced forward and forward tangents when produced backward meet, is called the point of intersection.

Angle of deflection : the angle which the forward tangent deflects is called deflection angle of the curve. It may be either to the left or the right. Point of curvature: it is the point on the back tangent at the beginning of the curve, where the alignment changes from a tangents to a curve. The points of curvature is also called the point of curve.

Point of tangency : it is the point on the forward tangent at the end curve where the alignment changes from a curve to a tangent. Tangent distance: it is the distance between the point of curvature and the point of intersection. It is also equal to the the distance between the point of tangency and the point of intersection Length of the curve : the total length of the cure from the point curvature to the point tangency is called length of the curve.

Long chord :the chord joining the point of the curvature and the point of tangency is called long chord Normal chord: a chord between two successive regular pegs on the curve is called a normal chord Mid-ordinate : it is distance between middle point of curve and the middle point of the long chord.

Sub chord : when a chord is shorter than the normal chord it is called short chord. This sub chord generally occur at the beginning and the end of the curve. External distance : it is the distance the point intersection and the middle point c is the curve.

Right hand curve : if the curve deflects to the right of the direction of the progress of survey , it is called the right hand curve. Left hand curve : if the curve deflects to the left of the direction of the progress of survey , it is called the left hand curve.

Designation of a circular curve Radius of curve: the curvature is defined by stating the length of radius. This method is often employed in subdivision surveys and sometimes in highway work.  

Degree of curve: The angle a unit chord of length 30m. subtends at the centar of the circle formed by the curve is known as the degree of the curve. The degree of curve may be defined either with respect to a fixed length of an arc of the curve or with respect to a fixed length of a normal chord of the curve. When the unit chord subtends an angle of 1 it is called a one degree curve when the angle is 2 two degree of curve and so on.

Relation between the radius and degree of a curve Let the d be the angle subtended by an are of 30m. length of a circle whose radius is R. The total circumference of the circle =2πr 30m arc of the circumference makes an angle D =360/2πr*30 D =10800/2πr D =1718.9/R  

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