Top-down cracking predictions for airfield rigid pavements

Recent full-scale testing of airfield rigid pavements has demonstrated the possibility of top-down cracking in concrete slabs. The objective of this study was to identify critical gear positions that produced the maximum tensile stress on the top of airfield rigid pavements, given no initial curling. Three individual aircraft gear geometries (dual, dual tandem, and triple dual tandem) and four aircraft types-considering all their main landing gears (B-777, A-380, MD-11, and B-747)-were analyzed for several slab configuration, pavement geometry, and material assumptions. The two-dimensional finite element analysis results showed that consideration of the entire main landing gear of the aircraft was necessary if the top tensile stresses were to be predicted accurately, except for the B-777. The A-380 and MD-11 had the greatest top-to-bottom tensile stress ratios for the full-gear analysis (critical tensile stress at the transverse joint) when the body gears were placed on the same slab for the no-load transfer condition. A factorial analysis further demonstrated that the load transfer efficiency across the joints and the load configuration (single gear or full aircraft) were the most sensitive factors affecting the top tensile stress and top-to-bottom tensile stress ratios.