To optimise the strategy for maintaining structures in the national road network, a software program that assists with the planning of interventions is necessary. The financial resources allocated for maintenance must be employed in an optimal manner in order to assure maximal use of the network. The results of the software program depend on the quality of the technical and economic models used. As of today the economic models have been well studied. The technical models, however, have not yet been treated in a satisfactory manner.

A synthesis of different studies on damage types, their mechanisms and their evolution, will be used to obtain degradation curves with respect to time and to determine the dominant parameters that describe the condition state of various structural elements. While studying the interaction between these elements, a model of the condition state of the complete structures will be developed. This model will be formulated so that it can be integrated into a software program.

The model developed will be tested by applying it to existing structures, conducting a sensitivity analysis of the parameters and comparing the actual condition state of the structures, based on reliable past data, with the condition state evolution predicted by the model.