Modeling of Bond Stresses of Overlay–Bridge Deck System

This study investigated direct and indirect factors influencing the bond strength between the concrete overlay and the bridge deck by using finite element analysis (FEA) and experimental validation. In addition, it presents reliable guidelines for the required bond strength that is needed for concrete to avoid potential delamination under various possible induced stresses. The purpose of the FEA is to predict and correlate the live load– and shrinkage-induced stresses at the interface between the concrete overlay and the bridge deck and to correlate these induced stresses with the direct tensile bond strength of the overlay. Fifteen full-scale prototype bridge systems without and with various thicknesses of overlays were studied. In addition, 42 overlay–bridge deck slab segments were created considering the relative thickness ratio of the overlay to the bridge deck slab (t_overlay/t_slab) and the relative elastic modulus (E_overlay/E_slab). Also, 210 overlay–bridge deck slab segments were created considering t_overlay/t_slab, E_overlay/E_slab, and slab concrete compressive strength (f ‘ _c ). The effectiveness and accuracy of the FEA guideline models were compared with Fowler's guidelines. The FEA results reveal that the live load– and shrinkage-induced shear stresses are about 1.5 to 2.5 times the induced normal stresses, in good agreement with most of the published research. Overlay thicknesses of 38 and 63 mm (1.5 and 2.5 in.) were recommended as the minimum and maximum allowable thicknesses that will prevent the overlay from debonding when the deck is subjected to AASHTO HS-20 truck loading plus impact as well as shrinkage loading.