Design Bending Moments for the Long-Span Deck Slab on the Composite Two-Girder Bridge

The long-span deck slab for the two-girder composite bridge has different design bending moments compared to the short-span deck slab for the multi-girder composite bridge. This is because the effects disregarded in the design of the short-span deck slab become important in the design of the long-span deck slab. Those are the effects of flexural stiffness of the girders, the front and middle wheels, the number of design lanes, and the two-way action of the deck slab. Therefore, for the reasonable design of the long-span deck slab, those effects should be properly considered. This paper proposes, based on the numerical parametric analyses considering those effects, two design bending moment formulas in perpendicular and parallel to bridge axis for the long-span deck slab that has girder span length between 4 m and 12 m. Reasonable margin of safety based on reliability theory is applied to the proposed formulas. The proposed formulas are verified by the results of independent and detailed finite element analyses. The differences between the design formula in the code and the proposed are also discussed.