- 2072 Magh · 6 marks
Rankine's deflection angle data, 145°, 5°
Short answer
Deflection angle Δ = 35°, degree 5°/30 m arc gives R = 1718.87/5 = 343.77 m. T = 108.39 m, L = 210.00 m. T1 = 1471.61 m, T2 = 1681.61 m. Deflection angles by δ = 1718.87c/R min, rounded to 10″; final cumulative = Δ/2 = 17°30′00″.
Compute the data for setting out a simple circular curve by Rankine's deflection angle method from the following informations: Angle of intersection = 145°0' Chainage of point of intersection = 1580 m Degree of curve = 5° Least count of the theodolite = 10" Peg interval = 30 m
Angle of intersection (interior) = 145°, so deflection angle . Degree of curve 5° for a 30 m arc.
Elements
Deflection angles
minutes, rounded to the least count of 10″. Peg interval 30 m: first sub-chord m, last sub-chord m.
| Point (chainage, m) | Chord c (m) | δ = 1718.87c/R | Cumulative deflection |
|---|---|---|---|
| 1471.61 | - | - | 0°00′00″ |
| 1500.00 | 28.39 | 2°22′00″ | 2°22′00″ |
| 1530.00 | 30.00 | 2°30′00″ | 4°52′00″ |
| 1560.00 | 30.00 | 2°30′00″ | 7°22′00″ |
| 1590.00 | 30.00 | 2°30′00″ | 9°52′00″ |
| 1620.00 | 30.00 | 2°30′00″ | 12°22′00″ |
| 1650.00 | 30.00 | 2°30′00″ | 14°52′00″ |
| 1680.00 | 30.00 | 2°30′00″ | 17°22′00″ |
| 1681.61 | 1.61 | 0°08′00″ | 17°30′00″ |
Check: final deflection ; the table gives 17°30′00″.
Answer: m, m, m; T₁ = 1471.61 m, T₂ = 1681.61 m; deflection angles as tabulated.
✓ Answer checked by Claude Opus 5.5 (high effort)
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