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Tuesday, 26 March 2013

CURVES

Introduction

is a continuous of the straight lines and curves with a radius of a fixed or variable.


Purpose


to connect a straight line through th point of intersection which lies between two straight lines to allow the movement to reverse slowly in the horizontal and vertical direction.


Reasons for curve construction
    • physical state of hilly land, swampy
    • connecting the exit or entrance as the exit roads 'tolls'
    • avoiding the position of the detail remain such as building mosques, cemeteries
    • safety of road uses in order to travel more comfortable and secure

Definition
  • Horizontal curve
    • curves of constant radius requires to connect two straight set out on the ground
  • Vertical curves
    • the curves are designed and built to connect the straight lines with cicular curves
  • Transition curves
    • the curves are designed and made to join two different straight slope
Purpose
  • Horizontal curves
    • for the convenience of road users.
    • to connect the straight lines with a horizontal curve
  • Vertical curves
    • to avoid situation where a sudden change in the vehicle entering the curve from a straight round
  • Transition curve
    • to avoid the situation where a sudden change in the vehicle when it start down the road after climbing a hill or otherwise
Types
  • Horizontal curves
    • transition curves
    • circular curves
    • compound curves
    • reverse curves
  • Vertical curves
    • crest curves
    • sag curves
  • Transition curves
    • crest curves
    • sag / summit curves
Setting out method
  • Horizontal curves
    • offset from the Tangent Line
    • offset from the Long Chords Line
    • Deflection Angle method
    • Sub Chords Line method
  • Vertical curves
    • by Levelling
  • Transition curves
    • Deflection Angle method




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