Chapter 20, Problem 19P

An existing rural 4-lane highway is to be replaced by a 6-lane divided expressway (3 lanes in each direction). Traffic volume data on the highway indicate that the AADT (both directions) during the first year of operation is 24,000 with the following vehicle mix and axle loads.

$\text{Passenger cars}=\text{5}0\text{ percent}$

2-axle single-unit trucks $\left(\text{12},000\text{ lb}/\text{axle}\right)=\text{4}0\text{ percent}$

3-axle single-unit trucks $\left(\text{16},000\text{ lb}/\text{axle}\right)=\text{1}0\text{ percent}$

The vehicle mix is expected to remain the same throughout the design life of 20 years, although traffic is expected to grow at a rate of 3.5 percent annually. Using the AASHTO design procedure, determine the minimum depth of concrete pavement required for the design period of 20 years.

$\begin{array}{l}{P}_i=4.5 J=3.2\\ P_t=2.5 C_d=1.0\\ S_c^{\text{'}}=650{\text{lb}/\text{in}\text{.}}^{\text{2}} S_o=0.3\\ E_c=5\times {10}^6{\text{lb}/\text{in}\text{.}}^{\text{2}} R=95\%\\ k=130{\text{lb}/\text{in}\text{.}}^{\text{3}}\end{array}$