INTERFACE SHEAR-STRESS IN OVERLAID CONCRETE PAVEMENTS

Shear stresses at the inter-face between an existing concrete pavement and an overlay are calculated using the finite-element method for different loading conditions. The effects of vertical wheel loads, temperature loading, and wheel braking forces are considered. Perfect bonding between the overlay and the pavement is assumed. The pavement-overlay slab is modeled using thin plate elements for calculating the stresses due to the vertical wheel load and temperature gradient. In analysis for stresses due to wheel braking loads, the slab is modeled with solid elements. The results are checked against Cerrutti's closed-form solution in the case of horizontal wheel braking. The computed shear stresses at the pavement-overlay interface for typical values of pavement and overlay thicknesses, wheel loads, and thermal gradients are compared to reported values of shear strength of laboratory-prepared overlaid specimens. The shear stresses at the interface are found to be small in relation to the interfacial bond strength of laboratory-prepared overlaid specimens. The findings suggest that debonding in overlay construction in the field is likely to be caused by stress concentrations due to local defects.