How to Find Radius of Horizontal Curve | Highway Engineering | All About Civil Engineer

Summary

In this video, the host from 'All About Civil Engineer' demonstrates how to calculate the radius of a horizontal road curve, an essential step in highway construction for determining superelevation. The tutorial guides viewers through marking the curve's start and end points, measuring the chord length, finding the midpoint, and determining the perpendicular distance to the curve. Using these two field measurements, the radius is calculated step by step with a simple formula based on the Pythagoras theorem. The video includes a clear numerical example, making it easy for civil engineering students and professionals to understand and apply the method in real-world road design.

Takeaways

• 😀 The video is from the YouTube channel 'All About Civil Engineer.'
• 😀 The topic is about finding the radius of a horizontal curve in highway construction.
• 😀 The radius of a curve is needed to calculate superelevation on roads.
• 😀 Two points are marked on the curve: the start and end points.
• 😀 The distance between these two points is measured as the chord length (e.g., 70 meters).
• 😀 The midpoint of the chord is determined (half of the chord length, e.g., 35 meters).
• 😀 The perpendicular distance from the midpoint to the curve (height) is measured (e.g., 10 meters).
• 😀 A sketch is made labeling points along the curve (A, B, C, D, etc.) for clarity.
• 😀 The radius is calculated using the Pythagoras theorem formula: R = (F² + H²) / (2H).
• 😀 Step-by-step calculation: F = 35 m, H = 10 m, F² + H² = 1325, divide by 2H = 20, radius = 66.25 meters.
• 😀 Only two field measurements are needed: chord length and midpoint height.
• 😀 The formula assumes a circular curve and is practical for highway construction projects.
• 😀 The video encourages viewers to like and subscribe to the channel.

Q & A

What is the main topic of the video?

The video explains how to find the radius of a horizontal curve in highway construction and how it is used to calculate superelevation.

Why is it important to determine the radius of a horizontal curve?

The radius is essential for designing safe curves on roads and for calculating superelevation, which ensures vehicles can navigate the curve safely at design speeds.

What is the first step in measuring the horizontal curve on the field?

The first step is to mark two points: the start and the end of the curve, then measure the distance between them, which is called the chord length.

How do you find the midpoint of the chord?

The midpoint is found by taking half of the measured chord length. For example, if the chord length is 70 meters, the midpoint is at 35 meters.

What field measurements are needed to calculate the radius?

Only two measurements are needed: the chord length (distance from start to end of the curve) and the height from the chord midpoint to the curve center (H).

Which formula is used to calculate the radius of the horizontal curve?

The radius is calculated using the formula: R = (F² + H²) / (2H), where F is half the chord length and H is the distance from midpoint to road centerline.

How is the formula applied with the example values?

For F = 35 meters and H = 10 meters: R = (35² + 10²) / (2 × 10) = (1225 + 100) / 20 = 1325 / 20 = 66.25 meters.

Why is a sketch with labeled points recommended?

Labeling points (A, B, C, D, E) on a sketch helps visualize the curve, clarify measurements, and avoid confusion during calculation.

What does 'H' represent in the calculation?

'H' represents the height or distance from the midpoint of the chord to the road centerline (the apex of the curve).

How can the calculated radius be used in road design?

Once the radius is known, it can be used to determine the superelevation needed for the curve, ensuring the road is safe and drivable at the intended speed.