Please enable JavaScript.
Coggle requires JavaScript to display documents.
ROAD CURVES Name : Rabiatul Adawiyah Binti Rosdiee Matric No: A19EA0140 …
ROAD CURVES
Name : Rabiatul Adawiyah Binti Rosdiee
Matric No: A19EA0140
HORIZONTAL CURVES
provide smooth change in direction when travelling from one straight to another
Simple Curves
Circular
Reverse
Compound
Transition Curves
Clothoid or spiral
Cubic parabola
Lemniscate
The centrifugal force acting upon the vehicle is zero on straight and will change abruptly as soon as it enters the circular curve.
As such, vehicle can be overthrown or out-of-control if speed is too high
This problem can be solved by partly
replacing the circular curve with transition curve
.
The
main reason
for introducing
transition curves
is to ensure safety and comfort of drivers when negotiating road curves.
Superelevation
Elevating (raising) the outer part of the curve to reduce/eliminate centrifugal force in road construction
Setting out a circular curve
A process of marking (setting out) the centre line of a route at chosen intervals
Most common method ; radiation or known as deflection angle method
Involves the computation of the deflection angles from selected tangent
VERTICAL CURVES
Needed at intersections of grades or slopes to provide a gradual change from travelling from one grade line to another
provide adequate visibility or sighting distance and safety to the traffic
Two types of vertical curves
Crest Curve
grades meeting at summits
Sag Curve
grades meeting at valley
Factors that determine the length of vertical curves
Sighting Distance
Stopping sight distance
Overtaking sight distance
Comfort
reduce vertical radial force
only for sag curve
Standards
decide sight distance
use K values
JKR