Design of reinforced concrete bridge decks under moving loads

This paper presents design recommendations of non-composite reinforced concrete bridge decks subjected to fatigue due to moving loads. These recommendations are based on test results of 1/3- and 1/6.6- scale physical models of a full-scale 21.6-cm (8.5 in.) thick and 15.24-m (50-ft) long simply supported non-composite reinforced concrete deck. Concrete bridge decks should be designed to transfer the load in a two-way action. Experimental results show that the two-way slab action in the decks changes to a one-way action (transverse direction) as fatigue damage due to a moving wheel-load accumulates. It is recommended to adopt an isotropic steel reinforcing pattern. An isotropic reinforcing pattern with a steel ratio of 0.3 % (each top and bottom layer) in each direction appears to be adequate. A similar reinforcing amount and pattern is required by the Ontario bridge design Code. The required steel content is therefore reduced resulting in substantial savings in the bridge deck construction costs and improving the corrosion resistance in decks, especially in the presence of deicing chemicals. It appears that flexural cracking in the deck and bond failure at the steel-concrete interface are necessary and sufficient conditions for deck failure under traffic loads. It is, thus, highly desirable to preclude or at least limit cracking and maximize the bond strength of the steel rebars.