Title: Transitional Curve
1Transitional Curve
2Simple Curves
?
?
R
R1
R
R
R1
R2
Arc of curve
Compound curve
?
R2
R2
R1
R1
?
Reverse curve
3Spiral curve
composite curve
4Transitional curve 1-To accomplish gradually
transition from tangent to the curve. 2-To allow
gradual introduction of super elevation.
F centrifugal force
R
The smaller the radius the bigger the force.
5Super elevation
SE
bwidth
SESuper Elevation usually slopes between 2.5
7
Normal Force
Wmg
6Length of Transition Curve
y
LT
x
Slope 1100 1200 (usual for free way)
LT SEslope 1485 (for rail
way) Example If SE 50 cm LT0.5x10050m Or LT
0.5x200100m
7 Cubic Parabola Vvelocity. Crate of
change of acceleration . Rminumim Radius of
transition . ???? LT ?? ??????? ?????? ??? ???
??????? ????? ?????? ??????.
8Example The central circular arc of a composite
curve on a part of road width 7.3m designed
speed 85 km/h has a radius 700m. 1) calculate
the amount of super elevation that should be
built in the road and calculate the length of
Transitional curve if the rate of change of
acceleration 0.4 m/s3. Sol. , C0.4m/s3
b7.3m , v85km/h ,
g9.81m/s2 , R700m ????? ??
?????? ??????? ??? 8 ???? ?????? ???? ?? ????
??????? ?? ??? ??? 2.5-7???? ???? ?????? ??????
??? 7 ? ???? ????? ?????? ??????? ??? ?? ????
??? ?????? ?????? ???????? ??? ????????
9???? ???? ???? ????? ??? ????? ???????? ????????
?????? ???? ???? ????? ??? ??????? ??
????? ????? ???? ?????? ?????? ????
??????? ??? 51m ?
102)Calculate the data required to set-out the
transition curve by offset taken at 20m
intervalus along the tangent length. .Sol