Handbook of Civil Engineering Calculations

long chord, middle ordinate, and external distance, (b) Determine all the data necessary to

stake the curve if the chord distance between successive stations is to be 100 ft (30.5 m).

(c) Calculate all the data necessary to stake the curve if the arc distance between succes-

sive stations is to be 100 ft (30.5 m).

Calculation Procedure:

1. Determine the geometric properties of the curve
   Part a. Refer to Fig. 13: A is termed the point of curve (PC), B is the point of tangent (PT),
   and V the point of intersection (PI), or vertex. The notational system is A = intersection
   angle = angle between back and forward tangents = central angle AOB; R = radius of
   curve; T = tangent distance = AV= VB; C = long chord = AB; M = middle ordinate = DC;
   E = external distance = CV.
   From the geometric relationships,

T = R tan

1

M (19)

T = 1200(0.2493) = 299.2 ft (91.20 m)

Also

C = 21 ISm^1 M (20)

C = 2(1200)(0.2419) = 580.6 ft (176.97 m)

FIGURE 13. Circular curve.