Question

A rural 6-lane divided highway with AADT = 30,000 veh/ day, with composition [(80% PC – 1000 lb/axel), (15% 2-axle trucks – 10000 lb/axle), and (5% 3-axle trucks – 32,000 lb/axle). Considering growth factor = 4 %, and design period = 20 years, directional distribution factor = 0.60, lane distribution factor = 0.7. Calculate the total 18-kip ESAL/ lane

Answer 1

So we need to find out the design ESALS for different type of vehicle categories

We are given all the information, So put these into a table as follows with axle load per vehicle, number of vehicles,

GRN = Growth Rate Factor = [{(1 + Growth Rate) ^ Design life } - 1]/ Growth Rate

= (1.04²⁰ - 1)/0.04 = 29.778

No of cars/day = 80% of 30000 = 24000

No of 2 axle trucks/day = 15% of 30000 = 4500

No of 3 axle trucks/day = 5% of 30000 = 1500

Truck factor = total weight(in lb) due to the truck/18000

While doing the final calculations you must multipy by the No of vehicles in that category/day * directional factor * lane distribution factor.

So we have the following

Truck factor = 1000*2/18000 = 0.1111

For cars # of ESALS = 24000 * 06 * 0.7 * 0.111 * 365 * 29.778 = 12173279

Total # of ESAL's in design life = 71518011 ESALs

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