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2.51. Two straights intersect at a chainage of 2500 m with an angle of deflection as 40°. The straights are to be connected by a simple circular curve...
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To start, can anyone tell me what we're trying to find when connecting two straight paths with a circular curve?
We're looking for the radius and length of the curve, right?
Exactly! We also need to calculate the tangent lengths and the long chord. Let's break these parameters down.
What is the tangent length, and how do we find it?
Great question! The tangent length is the distance from the intersection point to the point where the curve begins. To find it, we can use trigonometric functions based on the deflection angle.
How does the deflection angle affect the radius?
The deflection angle defines how sharp the curve is. A larger angle generally means a smaller radius, leading to a sharper turn. Remember, for a basic formula: R = L / θ, where L is the length and θ is the deflection.
Can we calculate this together in class?
Yes, we will! This practical approach helps reinforce learning. Let's take some example data next.
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Now that we understand the concepts, let's apply them to our example with given intersection at 2500 m and a deflection angle of 40°.
What are the coordinates used for?
The coordinates will help us determine the exact position of the curve's center in relation to those straights. Knowing the coordinates of points where tangents meet allows precise calculations.
Can you guide us through the calculations?
Of course! First, calculate the radius using the formula mentioned. Then, we will derive the tangent lengths using trigonometric functions.
What else will we find?
We'll also determine the curve length and long chord by applying the basic curve principles. Remember, the long chord connects the two end points of the curve directly.
This is really useful!
Absolutely! By learning how to apply these formulas, you can tackle similar issues you'll encounter in project work.
Overview
Short Summary
This section focuses on the calculations involved in setting out a simple circular curve connecting two intersecting straight paths.
Medium Summary
The section covers the key parameters involved in the design of a simple circular curve, including the radius of the curve, tangent lengths, curve lengths, and the length of the long chord, structured through a practical context of intersecting straights.
Detailed Summary
In this section, we explore the procedure for connecting two straight lines with a simple circular curve, especially when they intersect at a specified angle. The primary aim is to derive essential parameters such as the radius of the curve, tangent lengths from the intersection point to the curve, the total circular curve length, and the long chord of the curve. We will use given coordinates and geometrical principles to establish these critical elements, which are fundamental in road design and construction, ensuring safe and efficient transportation pathways.
Key concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
- Deflection Angle:
The angle through which the straights meet.
- Tangent Length:
Distance from intersection to curve's start point.
- Radius of Curve:
Determines how sharp the curve is.
- Simple Circular Curve:
The fundamental type of curve in road design.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
Example 1: Calculate the radius of a curve connecting two straight roads that intersect at a 30° deflection angle, using a known length of 200 m.
Example 2: Given the tangent length of a curve, find the distance between the curve ends to calculate the long chord.
Memory aids
Flash Cards
Glossary
Radius of Curve (R)
The constant distance from the center of the curve to any point on its circumference.
Tangent Length
The distance from the intersection point to the nearest point on the curve.
Deflection Angle
The angle between the two straight lines intersecting at a point, before being joined by a curve.
Long Chord
The straight line distance between the two ends of the circular curve.
Simple Circular Curve
A curve having a constant radius, used to connect two straight sections.