Fatigue Behavior of Concrete Bridge Decks Cast on GFRP Stay-in-Place Structural Forms

The fatigue performance of concrete bridge decks with glass fiber–reinforced polymer (GFRP) stay-in-place structural forms replacing the bottom layer of rebar is studied. The forms were either flat plate with T-up ribs joined using lap splices or corrugated forms joined through pin-and-eye connections. The decks were supported by simulated precast girders, AASHTO Type III, spaced at 1,775 mm. Two surface preparations were examined for each GFRP form, either using adhesive coating that bonds to freshly cast concrete, or just cleaning the surface before casting. For the bonded deck with flat-ribbed forms, adhesive bond and mechanical fasteners were used at the lap splice, whereas lap splice of the unbonded deck had no adhesive or mechanical fasteners. All decks survived 3 million cycles at 123 kN service load of the CL625 design truck of the Canadian standard. The bonded flat-ribbed-form deck further survived additional 2 million cycles at a higher load simulating a larger girder spacing of 2,365 mm. Stiffness degradations were 9–33% with more reduction in unbonded specimens. Nonetheless, live load deflections of all specimens remained below $\mathrm{span}/\mathrm{1,600}$. The residual ultimate strengths after fatigue were reduced by 5% and 27% for the flat-ribbed and corrugated forms, respectively. However, these strengths remain 7 and 3 times higher than service load, respectively. Both the lap-splice and pin-and-eye connection survived fatigue. Concrete crack width at the top surface over the girders remained below the AASHTO limit of 0.3 mm.