The Importance of Continuous Slab Support and Load Transfer at Joints in the Performance of Thin Concrete Overlays

Studies on the structural performance of existing Portland cement concrete roads in South Africa (1) have shown that the traffic utilizing these roads is not the pnme initiator of structural failures. Factors such as construction, environment and slab support conditions are predominant in initiating structural failures. However, it is also obvious that without loading, failures cannot occur. Modeilnig of these pavement structures by finite element analyses and comparing it with design procedures normally employed, show an overestimation of load induced concrete tensile stress. This paper will address the modelling of a moving load on a thin concrete slab and the calculation of stress that develop within the pavement as a result of that. The modelling is extended to include the simulation of a small void beneath the slab and the resulting stresses which lead to failure. Modelling is followed by comparison with field performance and some speculative conclusions are made on the mechanism of failure and the suggested areas of detailed investigation necessary to arrive at an appropriate design procedure and laboratory testing of materials.