Paper by Tatsuo Nishizawa, Takato Ozeki, and Hirotaka Kawano from 10th ICCP Quebec 2012
In this study, possibility of top-down cracking in concrete pavement was investigated. The main cause of the crack is supposed to be tensile stress at the top of the concrete slab. 3DFEM simulations that took into account actual temperature distributions throughout slab depth were performed on concrete pavements for a heavy duty road and an international airport. Thermal stress analys is revealed that nonlinear negative temperature distribution produces relatively large tensile stress at the top of the slab, which cannot be precisely estimated by conventional thermal stress equations based on the linear temperature distribution. Areas where the bottom surface of concrete slab was separated from the surface of underlying layer were very small, because the underlying layer deformed similarly as the slabs deformed and reduced the gap area. The combined stresses were also calculated with the application of both wheel and thermal loads. The maximum top combined stress occurred at a position away from the wheel loads. The ratio of the top combined stress in negative temperature gradient to the bottom combined stress in positive temperature gradient is greater in the airport pavement than that in the road pavement. The installation of dowels in joints reduced the combined stress in the loaded slab. Demonstration for ISCP Board only.