Materials and Road Research

Materials and Road Research | Pavement Design

Pavement Design

The Effect of reliability on MnPAVE design thickness

In MnPAVE, the recommended design reliability changes depending on traffic levels.

MnPAVE Flexible

The Preliminary Design value is automatically calculated whenever a design input is changed. When this value equals the Design Life in Project Information, the simulated reliability will approximate the Recommended Minimum Reliability.

To accomplish this, the thickness and modulus values used to simulate pavement responses are reduced. The confidence level in Table 1 determines how much these values will be reduced. It refers to the percentage of randomly-selected thickness or modulus values that will be equal to or greater than the design values.

Most of the time, a change in Flexible ESALs will result in a predictable change in Preliminary Design. However, when one of the traffic thresholds in the table is crossed, this value will change more than expected.

MnPAVE Rigid

In MnPAVE Rigid, traffic loads are not simulated as they are in MnPAVE Flexible. Thousands of simulations were conducted at the University of Minnesota using the Mechanistic-Empirical Pavement Design Guide (MEPDG), an early version of AASHTOWare Pavement ME Design which was calibrated for Minnesota rigid pavement designs. MnPAVE uses the results of these simulations to determine the rigid design thickness. MN/RC 2014-27 summary and report

The reliability levels for these designs were determined by traffic level and location. In addition, the level of cracking used to indicate the end of the pavement life differs by location. Table 2 lists these differences.

For these reasons, changes in traffic and location may result in a larger than expected change in design thickness.