# UNIT 4 CURVES CURVES Curves generally used to

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UNIT – 4 CURVES

CURVES Curves generally used to change the direction in highway or in railway also in irrigation canal OR the geometrical arc provided at the intersection of 2 straight of communication rout such as road, rlys, canals etc. is called as curve

Necessity 1. To introduce smooth & gradual change in direction of routes 2. To introduce smooth & gradual change in slope or gradient of route 3. In a straight route, if costly land comes in the way, then it can be avoided by providing diversions with help of curves 4. Track or road made stable safe of hill by changing alignment 5. Reduces accidents

Function 1. Provided so as to get comfort of passenger 2. Provided so to get easy turning in case of roads 3. Gradual change direction or orientation in the alignment can be made by providing curves 4. Provide safty comfort & convenience

Types

Simple curve Curve consist of a single arc of a circle of which 2 straight tangents further connects & brings about a deflection of road through an angle θ is called simple curve

Compound curve Curve consist of 2 & more simple curves of diffnt radius curving in same direction is called In compound curve 2 adjacent curves will have a common tangent BC centre of 2 adjacent curve lie on same side of curve

Reverse curve Curve consist of simple curve having equal or different radius turning in opposite directn is called

transition curve Curve having variable radius is called OR radius varies infinity to finite value equal to that of circular curve to be connected & vice versa is termed

lemniscate curve Curve is similar to transition curve, generally adopted in city roads where deflection angle is large

vertical curve Valley curve: curve having convex surface on downward side is called Summit curve: curve having convex surface on upward side is called

Definition & Explanation of different terms Degree of curve: the angle subtended at the centre by a standard chord of 30 m length