‘Point of curve’ of a simple circular curve is
Point of commencement
Understanding the Point of Curve in Surveying
In the field of civil engineering and surveying, particularly when designing or laying out roads and railways, simple circular curves are used to provide a smooth transition between two straight sections (tangents). The question asks to identify what the ‘Point of curve’ refers to in a simple circular curve.
Point of Curve Definition
The Point of curve is a fundamental term used in horizontal curve design. It specifically designates the exact location where the initial straight section (known as the back tangent) ends, and the circular curve begins. This point marks the commencement of the curve, hence it is also widely known as the Point of commencement.
- It is often abbreviated as PC in surveying notes and plans.
- It serves as the starting reference point for measuring distances along the curve.
- Before this point, the alignment is a straight line (tangent); after this point, the alignment follows a circular arc.
Other Key Points in a Simple Circular Curve
To fully grasp the geometry of a simple circular curve, it's helpful to understand its other defining points:
| Term | Common Abbreviation | Description |
|---|---|---|
| Point of Commencement | PC | This is the beginning of the circular curve, where the back tangent transitions into the curve. It is synonymous with the ‘Point of curve’. |
| Point of Tangency | PT | This marks the end of the circular curve, where the curve transitions back into a straight section (the forward tangent). |
| Point of Intersection | PI or V | This is the theoretical point where the back tangent and the forward tangent would intersect if extended. It is also referred to as the Vertex. |
Understanding these specific points is crucial for the accurate design and layout of simple circular curves in various infrastructure projects.
Conclusion on Point of Curve
Based on standard surveying and highway engineering practices, the ‘Point of curve’ is the initial point of the circular arc where the alignment deviates from the tangent. This point is correctly identified as the ‘Point of commencement’.
Important Questions from Curves
If chainage of PC is 40000 m and length of transition curve is 220 m, then the chainage of junction of transition curve is______.
In a compound curve construction, if the length of the first curve is 268.3m and chainage at point of curve is 623.3m. The chainage at point of compound curvature is_______.
The point where the road alignment changes from a tangent to a curve is known as _________
Calculate the length (m) of tangent of a 5-degree curve, if the deflection angle is 60 degree.
What is the value of mid-ordinate, If the radius of a simple circular curve – 560 m and the deflection angle = 120°
