Pavement layer moduli backcalculation using Falling Weight Deflectometer (FWD) data is widely used among the pavement engineering community to evaluate the structural capacity of existing pavements and the backcalculated layer moduli provide valuable information for highway engineers when they perform rehabilitation and reconstruction designs. The selected backcalculation algorithm is based on a sound engineering model to simulate the actual pavement structure so that the representative layer moduli are backcalculated for rehabilitation and reconstruction designs. Different types of pavements respond differently to temperature changes. The resilient modulus of asphalt concrete (AC) changes dramatically as the temperature changes while the concrete resilient modulus is not so sensitive to the temperature change. But the concrete slabs curl up or down due to the changing temperature gradient, which changes the contact condition between the slabs and the underlying layer. The slab-on-grade model is often used for Jointed Concrete Pavements (JCP) to backcalculate layer moduli, which assumes that the concrete slabs are lying flat and in full contact with the underlying layer. The proposed data analysis is to incorporate a curling factor in the algorithm when backcalculating layer moduli using the Long-Term Pavement Performances (LTPP's) FWD data under the Seasonal Monitoring Program (SMP) for the JCP sections. The curling factor, an equivalent temperature gradient, will be backcalculated in addition to the layer moduli in this algorithm. The curling factor will account for the FWD data variation within a day so that a constant set of layer moduli are backcalculated for a single testing day. The constant set of layer moduli are more representative for use in the evaluation of existing JCP and the curling factor provides useful information as regard to the curling susceptibility of the JCP.
To provide a formalized backcalculation procedure that incorporates resultant temperature gradient.