Eg:
Calculate superelevation for a road having a radius of a curve as 150m. The design speed is 60km/hr. The coefficient of lateral friction is 0.15.
To find :
Superelevation=e =?
Calculation:
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The formula to calculate the superelevation of the road is
[e + f ] = [V² / 127R]
Where,
e = rate of superelevation =?
f = lateral friction factor = 0.15
V = Velocity of vehicle in km / hr. = 60km/hr
R = Radius of a circular curve in meters.= 150m.
[e + f ]= [V² / 127R]
[e + 0.15] = [60² ÷ 127 х 150 ]
[e + 0.15] = [3600 ÷ 19,050]
[e + 0.15] = 0.189
e = [0.189 - 0.15]
= 0.0389
Required slope = 1/0.0389
= 1 in 25.70
Superelevation in %
= [0.0389 х 100]
= 3.89%
According to IRC, the maximum allowable superelevations for mixed traffic over hills & terrains is 7%.
e = 3.89% < 7% hence safe.
Thank you for going through these calculation steps❤. Have a good day 😄.
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