Billions of Euros are spent every year on constructing and maintaining the European road network. In order to guarantee the safety and quality of this vast network over the long term and within acceptable budgetary limits, performance assessment tools need to be made available to decision-makers. Several advanced pavement deterioration and response models have been developed in recent years, but they describe only a limited number of failure phenomena and sometimes require large computational facilities. The need for a more comprehensive mechanistic pavement design model has been recognised by the European Commission and two actions involving co-operation between several European countries, COST 333 and AMADEUS, have been supported.
The main objectives of AMADEUS were:
- to evaluate existing, advanced, analytical pavement design models by comparing their predictions using standard inputs - looking at the ability of these models to deal with different materials, pavement constructions, climate and traffic characteristics;
- to issue recommendations and guidelines to promote the appropriate use of these design models;
- to set up the elements for a comprehensive design method integrating a number of distress phenomena with their evolution and mutual interactions.
As a result of the AMADEUS project, a number of advanced pavement design models and corresponding software packages have been evaluated. This evaluation has addressed issues related to the use of the software, the input availability and complexity, and also validation of the models for relevant situations, through the comparison of their output with measured data. A major outcome of the project is the production of guidelines for potential users of the models evaluated, comprising both practical aspects related to the use of the software, and advice concerning which situations related to pavement design can be addressed by the model.
The inventory of existing tools reveals a wide variety of products in terms of response models and the types of damage they address, but none of them account for all damage types nor do they take into account their mutual interactions. Models based on the multi-layer elastic theory are easy to use and generally give similar results. Some of these models, however, have limitations in precision or produce wrong results in stress/strain analysis at particular locations of the structure (particularly in the vicinity of the applied loads and in the subgrade). Models based on finite element approaches generally provide better results (especially the three-dimensional methods), but are more difficult to apply unless users have a thorough knowledge of basic principles.
The AMADEUS project has set up the plans for a comprehensive and practical pavement design procedure for Europe. The new method will be able to make a better prediction of pavement performance, taking into consideration the material and structural alterations that occur during the life cycle of the pavement. Further research is needed in order to be able to describe more accurately the deterioration mechanisms that pavement components undergo during their life cycle. The comprehensive design method proposed by AMADEUS should be developed in stages and in a manner that enables it to be upgraded when significant developments occur. The project will be followed up in the COST 333 Action, 'Development of New Bituminous Pavement Design Method'.
AMADEUS guidelines can be used directly by different professionals working in the field of pavement design:
- Engineers will find practical guidance on which models may be best suited for solving a specific problem related to pavement design and performance, the input necessary to run the available software, and the difficulties that may be encountered when using it.
- Researchers will be able to identify topics related to pavement design that are not yet addressed by the current state of the art and therefore need further investigation.