Question

1. (Source: Potter) A coal-fired power plant is served by 25 trucks. When loaded, each truck consists of one single-axle of 14 kips (the front axle), two tandem axles of 32 kips each (the middle axles) and one single axle of 22 kips (back axle). Each truck makes 25 daily trips. The weights on the same axles when the truck is empty and leaving the power plant are 10 kips, 12 kips, and 8 kips, respectively. A twolane road is to be designed to serve the power plant and to last for a period of 10 years. a) What is the equivalency factor for the 14 kip single axle? b) What is the load equivalency factor for the 32 kip tandem axle? c) What is the design ESAL (for 10 years) for the incoming traffic? d) What is the design ESAL (for 10 years) for the outgoing traffic? 2. For the above problem, structural number, SN for incoming traffic is 5.0 and SN for outgoi traffic is 3.0. The design engineer used the following material for road construction. A 12-inch crushed stone sub-base with layer coefficient of 0.10 A 6-inch crushed stone base A hot-mix asphalt-concrete (wearing) surface layer . a. What is the required asphalt thickness for the incoming traffic? b. What is the required asphalt thickness for the outgoing traffic? For the material data given, what is the required gravel thickness that will produce the same SN as a one-inch thick asphalt concrete layer?

2

Answer 1

2) Given, SN POS incoming traffic - 5.0 SN fos outyoning traffic = 3.0 Crushed stone sub-base = 18 in Layes coefte. -0.10 crushed stone base = bin Hot-mix asphalt concrete (wearing suspace layes a) SN= a, D,+ aq dq me + 0₂ 03 M₂ 5.0 = (0.44) 2, +0:1)6)(1.0) + (0.1) (12)(1.0) 0,= 2.00 = 4.64 in 0.44 b) SN= a, D, + aq Qq me t a3₂ M₂ 3.0 =(0.44) D,+(0.14)6)(1-0) +6 -1) (2) (-0) 0,= 0.96 =2.18 in 0.44 - 1-inch thick asphalt layes (0.44) () = (0-1) (~) X= 4 in . Remired gravel thickness = 4 in