Week 1 Challenge

1.Create a design summary report (DSR) for the following items for any highway you are aware of in your region. Mention the highway name, and location: -

1. Category/Class of the road.
2. Design speed of the road.
3. Terrain classification.
4. Travel Lane width.
5. Typical min. cross slope.
6. Horizontal curve radius without superelevation.

Ans:

Name of the Road: GMR Hyderabad Vijayawada Expressways Private Limited

Category/ Class of the Road: Expressway

The design speed of the road: 120 km/hrs at plain terrain and 80 km/hrs at hilly terrain

Terrain classification: Plain & Hilly

Travel Lane width: 4-lane (expandable to 6) with paved and unpaved shoulders on both sides, with each lane width of 3.5m.

Typical min. cross slope: Minimum Cross Slope of 2.5% (as per IRC SP 99)

Horizontal curve radius without superelevation: Generally Max radius where no SE is needed for 120KMPH design Speed and min cross slope of 2.5% is 4000m

2. What is the typical roadway project life cycle workflow? List out in points. What is the typical roadway design workflow? Also, list out all the experts needed on a roadway project.

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3.What are the important geometrical parameters of a horizontal alignment and vertical profile? When is a vertical curve needed? List the formula with a diagram for vertical curve. List all types of vertical curves with the diagrams.

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4.When is superelevation necessary? Show diagrammatical presentation of super concept.

Ans: Superelevation works with several interacting forces of physics to help drivers maintain speed and stay safely on the road through a curve. A complex combination of centrifugal and centripetal force, friction, inertia, weight, and velocity or speed all interplay to determine the need for superelevation on a road or highway.

For equilibrium condition in the transverse direction,

W*sinθ - P*cosθ + Ff1 + Ff2 = 0

P*cosθ - W*sinθ = R1 + R2

P*cosθ - W*sinθ = fN1 + fN2

P*cosθ - W*sinθ = f*(N1+N2)

P*cosθ - W*sinθ = f*(P*sinθ + W*cosθ)

P*cosθ - f*P*sinθ = W*sinθ + f*W*cosθ

P/W = (sinθ + f*cosθ)/(cosθ - f*sinθ), dividing by cosθ on R.H.S.,

(v^2)/gR = (tanθ + f)/(1 - f*tanθ)

Substituting tanθ = e,

v^2/(gR) = (e + f)/(1 - e*f)

As per I.R.C., f=0.15 and e is limited to 0.07 (for plain and rolling zone). Therefore e*f becomes 1.

v^2/(gR) = e + f

Superelevation Formula

e = rate of superelevation

f = design value of coefficient of lateral friction = 0.15

v = design speed of the vehicle, m/sec

R = radius of the horizontal curve, m

g = acceleration due to gravity = 9.8 m/sec^2

Substituting g = 9.8 and converting v to kmph, we get,

Superelevation formula simplified

v = design speed of the vehicle, kmph

R = radius of the horizontal curve, m

With these formulas, e value could be found out. If f is taken as 0 (zero), then equilibrium superelevation could be found out. Suitable radius (R) for the constrained values of e and f could also be found out.

5.List out the typical set of submission needed for a roadway project.

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6.Draw a typical cross section with following parameters –

1. 12’ travel lane
2. 10’ shoulder lane
3. 2% cross slope
4. 2’ berm
5. End conditions with cut/fill of 6:1 and 4:1
6. Ditch condition of front slope 4:1, back slope 4:1, 3:1

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