Per Ullidtz - Dynatest International

Pavements deteriorate under trafic loading due to the stresses and strains in the pavement layers. The mechanistic-empirical method captures this failure mechanism, and is now widely accepted all over the world. In the mechanistic step, a mathematical model is used to calculate the critical Stresses and strains, which are them used with empirical relationships to predict the pavement deterioration . Both of the two steps in the mechanistic – empirical method are important and both of the two steps in the mechanic- empirical method are important and both require careful consideration. This paper will describe some of the problems associated with both steps. For the mechanistic step the emphasis will be on determining layer moduli from falling weight Deflectometer (FWD) testing the importance of non – linear elastic subgrade materials will be highlighted, both with respect to deriving correct layer moduli and for calculation of the critical stresses and strains. The paper will also discuss mtws ef? extmdhg the mechanistic part of the method to include full load spectra, climatic effects and influence of ageing and of gradual deterioration . Having the mechanistic part, reducing the number of parameters that influence he empirical relationships facilitates the calibration of these relationships, for example through the use of accelerated pavement tests (APT). finally the paper will show how, relatively simple, damage models, based on the mechanistic-empirical method, can be used in a Pavement Management System (PMS) for planning the long term maintenance and rehabilitation of a highway network, and how the PMS itself can be used for improving the damage functions and thus to reduce the overall costs of road transportation.