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 dif ferent loading conditions. The effects of vertical wheel loads, temper ature loading, and wheel braking forces are considered. Perfect bondin g between the overlay and the pavement is assumed. The pavement-overla y slab is modeled using thin plate elements for calculating the stress es due to the vertical wheel load and temperature gradient. In analysi s for stresses due to wheel braking loads, the slab is modeled with so lid elements. The results are checked against Cerrutti's closed-form s olution in the case of horizontal wheel braking. The computed shear st resses at the pavement-overlay interface for typical values of pavemen t and overlay thicknesses, wheel loads, and thermal gradients are comp ared to reported values of shear strength of laboratory-prepared overl aid specimens. The shear stresses at the interface are found to be sma ll in relation to the interfacial bond strength of laboratory-prepared overlaid specimens. The findings suggest that debonding in overlay co nstruction in the field is likely to be caused by stress concentration s due to local defects.