Transition curve and Superelevation
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The document discusses transition curves, which are variable radius curves used to gradually change a vehicle's path from a straight line to a circular curve, thus minimizing discomfort caused by centrifugal forces. It outlines the objectives and benefits of transition curves and superelevation, including improved vehicle stability, comfort, and safety at higher speeds. The text also details the properties, types, and calculations related to determining the length of transition curves and superelevation rates.
![Ex:1
• Calculate the length of transition curve for
V=65kmph, R=220m, rate of introduction of
super elevation is 1 in 150, W+We= 7.5 m.
(Hint: c=0.57)
• [Answer: Ls1=47.1m, Ls2=39m (e=0.07,
pavement rotated with reference to
centerline), Ls3=51.9m, Ls =52m]](https://image.slidesharecdn.com/transitioncurve-210816162648/85/Transition-curve-and-Superelevation-31-320.jpg)
![Ex:2
• NH passing through rolling terrain of heavy
rainfall area, R=500m. Design length of
Transition curve. (Hint: Heavy rainfall.
Pavement surface rotated with respect to
inner edge. V=80kmph, W=7.0m, N=1 in 150)
[Answer: c = 0.52, Ls1 = 42.3, Ls2 = 63.7m(e =
0.057, W+We = 7.45), Ls3 = 34.6m, Ls = 64m]](https://image.slidesharecdn.com/transitioncurve-210816162648/85/Transition-curve-and-Superelevation-32-320.jpg)
Transition curve and Superelevation
- 1. Transition Curve & Superelevation Batch 2019 QUEST Larkana 2019 Batch
- 2. Transition Curve • A curve of Variable Radius is known as Transition curve. • Transition curve is a curve in plan which is provided to change the horizontal alignment from straight to circular curve gradually means the radius of transition curve varies between infinity to R or R to infinity.
- 3. • As soon as a vehicle commences motion on a circular curve from a straight line track, it is subjected to a sudden centrifugal force, which not only causes discomfort to the passengers but also distorts the track alignment and affects the stability of the rolling stock. • In order to smoothen the shift from the straight line to the curve, transition curves are provided on either side of the circular curve so that the centrifugal force is built up gradually.
- 4. Transition Curve • A transition curve is, therefore, the cure for an uncomfortable ride, in which the degree of the curvature and the gain of superelevation are uniform throughout its length, starting from zero at the tangent point to the specified value at the circular curve. The following are the objectives of a transition curve.
- 6. Objectives of Transition Curve • To decrease the radius of the curvature gradually in a planned way from infinity at the straight line to the specified value of the radius of a circular curve in order to help the vehicle negotiate the curve smoothly. • To provide a gradual increase of the superelevation starting from zero at the straight line to the desired superelevation at the circular curve.
- 7. • To ensure a gradual increase or decrease of centrifugal forces so as to enable the vehicles to negotiate a curve smoothly. • To introduce extra widening gradually • To provide comfort for the driver that is to enable smooth vehicle operation on road. • To prevent the possibility of overturning of vehicles on horizontal curve. • To improve in design speed on horizontal curves. • Reduce wear and tear of rail section .
- 8. Properties Of Transition Curve • 1)Rate of change of Super elevation must equal to that curve. • 2) Radius of Transition curve at junction should equal to radius of circular curve. • 3) Must meet the circular curve tangentially. • 4) Length of Transition Curve is inversely proportional to Radius.
- 9. Types Of Transition Curve • a) Spiral or clothoid • b) Cubic parabola • c) Lemniscates
- 10. Spiral or clothoid Ideal Transition Curve Why? • Rate of change or centrifugal acceleration is consistent (smooth)and • Radius of the transition curve is Infinity at the straight edge and changes to R (Ls ∝ 1/R) at the curve point and calculation and field implementation is very easy. • It satisfies that rate of change of centrifugal acceleration is constant.
- 11. Ideal Curve
- 12. Lemniscate Curve
- 13. All in One
- 14. Length Of Transition Curve For mountainous and steep terrain Ls = V²/R
- 15. Length Of Transition Curve • b) By definite Rate of Superelevation • Ls = nh/100 • Wher n = rate of Superelevation 1 in n and h = superelevation • C) By Arbitrary Gradient Ls = hv/x • Where x = time rate in cm/sec which can varey from 2.5 cm/sec to 5 cm/sec.
- 16. Length Of Transition Curve • D) Based on rate of change of superelevation and extra widening: • Ls =( W+We)nh • The maximum of above conditions will be considered as the length of transition curve.
- 17. Shift and Length
- 18. Superelevation • The inward transverse inclination provided to the cross-section of the carriage way at horizontal curved portion of a road is called superelevation, cant or banking . • In other words superelevation is raising of outer edge (of curved portion of road of railway) with respect to its inner edge is called superelevation. It is generally denoted by the ‘e
- 19. Superelevation
- 20. Superelevation
- 21. Objective of providing superelevation • 1.To counteract the effect of centrifugal force acting on the moving vehicle to pull the same outward on a horizontal curve. • 2. To help a fast moving vehicle to negotiate a curved path without overturning and skidding. • 3. To ensure safety of the fast moving vehicle. • 4. To prevent damaging effect on the road surface due to improper distribution of load.
- 22. Advantages of providing superelevation • It permits running of vehicle at high speed on a curved path or a straight path without any danger of overturning and thus results into increased volume of traffic. • It also helps to keep the vehicle to their proper side on the pavement and thus prevents collision of vehicles moving in opposite direction on a curved portion of the road. • It provides drainage of the whole width of the road towards the inner side. Thus, there is no necessity of providing side drain on the outerside of the road.
- 27. From width and superelevation rate or rising slope • e, or h = 1/n x width of road
- 31. Ex:1 • Calculate the length of transition curve for V=65kmph, R=220m, rate of introduction of super elevation is 1 in 150, W+We= 7.5 m. (Hint: c=0.57) • [Answer: Ls1=47.1m, Ls2=39m (e=0.07, pavement rotated with reference to centerline), Ls3=51.9m, Ls =52m]
- 32. Ex:2 • NH passing through rolling terrain of heavy rainfall area, R=500m. Design length of Transition curve. (Hint: Heavy rainfall. Pavement surface rotated with respect to inner edge. V=80kmph, W=7.0m, N=1 in 150) [Answer: c = 0.52, Ls1 = 42.3, Ls2 = 63.7m(e = 0.057, W+We = 7.45), Ls3 = 34.6m, Ls = 64m]