- 2073 Magh · 6 marks
Rankine's method table, 150° intersection, 3°
Short answer
Deflection angle Δ = 30°, degree of curve 3° for 20 m chord gives radius R = 180×20/(π×3) = 381.97 m. Tangent T = 102.35 m, curve length L = 200.00 m. T₁ chainage 1482.65 m, T₂ 1682.65 m. Deflection angles are computed per chord using δ = 1718.87c/R minutes, with final cumulative angle 15°00′00″.
Compute and tabulate the data required for setting out a simple circular curve by Rankine's Method from the following information: Angle of intersection = 150°00' Chainage of point of intersection = 1585.00 m Degree of curve = 3° Peg interval = 20 m, Normal chord = 20 m
Angle of intersection (interior) = 150°, so deflection angle . The degree of curve is taken for the normal chord (arc) of 20 m.
Elements
Rankine's deflection angles
minutes for a chord . First sub-chord m (to the next 20 m peg), last sub-chord m.
| Point (chainage, m) | Chord c (m) | δ = 1718.87c/R | Cumulative deflection |
|---|---|---|---|
| 1482.65 | - | - | 0°00′00″ |
| 1500.00 | 17.35 | 1°18′04″ | 1°18′04″ |
| 1520.00 | 20.00 | 1°30′00″ | 2°48′04″ |
| 1540.00 | 20.00 | 1°30′00″ | 4°18′04″ |
| 1560.00 | 20.00 | 1°30′00″ | 5°48′04″ |
| 1580.00 | 20.00 | 1°30′00″ | 7°18′04″ |
| 1600.00 | 20.00 | 1°30′00″ | 8°48′04″ |
| 1620.00 | 20.00 | 1°30′00″ | 10°18′04″ |
| 1640.00 | 20.00 | 1°30′00″ | 11°48′04″ |
| 1660.00 | 20.00 | 1°30′00″ | 13°18′04″ |
| 1680.00 | 20.00 | 1°30′00″ | 14°48′04″ |
| 1682.65 | 2.65 | 0°11′56″ | 15°00′00″ |
Check: final deflection (computed 15°00′00″).
Answer: m, m, m, T₁ at 1482.65 m, T₂ at 1682.65 m; deflection angles as tabulated.
✓ Answer checked by Claude Opus 5.5 (high effort)
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