Improvement to method of equivalent thicknesses (MET) for calculation of critical strains for flexible pavements

Abstract

This paper presents the results of a sensitivity analysis carried out to compare the values of asphalt and subgrade strains (as well as associated fatigue and deformation lives) obtained with the method of equivalent thicknesses (MET) with those calculated with the BISAR software. The strains were calculated for a large number of 3-layer flexible pavement structures. A linear regression analysis has been performed to predict the values of strain (as well as life) calculated with BISAR from those obtained with the MET methodology and with a desired level of confidence. The analysis showed that, while subgrade strains were predicted acceptably well, differences greater than ±10% exist between the two methods in the case of the asphalt strains. An alternative model is therefore proposed to improve the MET methodology results for 3-layer pavement structures. The alternative model provides a simple and efficient method for practical purposes, for example in Pavement Management Systems or in simulation of pavement deterioration, where stresses and strains must be calculated large numbers of times.

Keywords:

• Method of equivalent thicknesses (MET)
• BISAR
• strain
• life
• layered analytical models (LAM)