As a first stage in verification of Road and Hydraulic Engineering Division of the Dutch Ministry of Transport and Public Works (RHED) structural design method, an overall analysis has been made of SHRP-NL method. This has been supplemented with a limited number of previously analysed test sections. For 189 sections, pavement fatigue strengths have been determined from back calculated construction data. They have been compared with cumulative traffic load to determine theoretical degree of fatigue. Structural damage has been assessed from visual inspection and drilled cores. In practically none of test sections is critical ratio between cumulative traffic load and fatigue strength approached; there is often much extra implicit safety in design because of conservative design parameters, and many pavements receive an overlay for other than structural reasons. Cracking found on many test sections can be explained as surface originated. In pavements with asphaltic concrete courses thicker than 0.16 m, cracking is almost always confined to surface courses, while in thinner courses cracking rapidly propagates downwards through full pavement depth. Test sections are well representative of Dutch roads concerning construction, traffic load and age. The main conclusion is therefore that in common design practice fatigue is rarely or never the predominant failure mechanism. The main cause of structural distress is surface cracking. Further research should concentrate on surface cracking.
Abstract