SETTING OUT OF CURVE

                                     SETTING OUT OF CURVE

Through this post you are going to learn 

1. What is curve setting ?

2. Type of curve in surveying or classification of curve?

3. Degree of curve .

4. Relation between Radius and degree of curve ?

4. What are the different method of curve setting?

1. What is curve setting ?

Let's assume AB is the direction of a road or railway . Due to some obstacle or some unavoidable circumstance we can not go forward . This is why we have to shift the direction of our road . The angle of change in the direction is known as deflection angle . This angle denoted as Φ . A vehicle to run easily along the road or railway trake these two line are connected by an arc this arc is known as a curve of a road or you can say Setting out of curve  .

2. Types of curve in surveying 

Generally curve are two type 

 i. Horizontal Curve 

ii. Vertical Curve 

    When the curve is provided into the horizontal plane is known as Horizontal Curve  . 

and horizontal curve are five types 

a. Simple Curve

b. Compound Curve 

c. Revers Curve 

d. Transition Curve 

e. Lemniscate Curve 

a. Simple Curve 

When a curve consists of a single arc with a constant radius connecting the two tangents , it is said to be a Simple Circular Curve .

b. Compound Curve

When a curve consists two or more arcs with different radius is said to be Compound Curve .

c. Revers Curve

Reverse curve is the curve where

1.Two arc are bending in opposite direction 

2.Their centre lie on opposite side 

3.May be their radius either equal or different

4.The have one common tangent 

d. Transition Curve

A Curve of variable Radius is called Transition Curve .

e. Lemniscate Curve 

A Lemniscate curve is similar to the Transition Curve and this is generally adopted in city where the diflection angle is large .

3. Degree of curve .

For the unit chord length 30 m , the angle formed at the centre of the circle by the curve is known as Degree of Curve .

4. Relation between Radius and degree of curve ?

Let AB is the unit Chord of the length 30m ,

O = Centre

AB = 30m                

AC = 𝟏/𝟐×𝐴𝐵

AC =1/2×30 = 15

From the triangle AOC

𝑺𝒊𝒏𝑫/𝟐= 𝑨𝑪/𝑶𝑨

𝑺𝒊𝒏𝑫/𝟐 =𝟏𝟓/𝑹

 

When D is very small then 𝑺𝒊𝒏𝑫/𝟐  𝑚𝑎𝑦 𝑏𝑒 𝑡𝑎𝑘𝑒𝑛 𝑎𝑠 𝑫/𝟐  𝑅adian

So ,

R =𝟏𝟓/((𝑫/𝟐)×(𝝅/𝟏𝟖𝟎) )

R = 𝟏𝟕𝟏𝟗/𝑫   (𝒂𝒑𝒑𝒓𝒐𝒙) 

4. What are the different method of curve            setting?

The following are the general method employed for setting out curves by chain and tape method 

a. Taking offset or ordinate from the long chord 

b. Taking offset from the chord produced 

c. Successively bisecting the arcs

d. Taking offset from the tangent .

       to know every method of curve settion click on the  METHOD BUTTON