General

Reinforced concrete deck slabs must not only be designed for dead and live loads at the service and strength limit states, the AASHTO LRFD (7th Edition, 2014) requires that the deck also be designed for a vehicular collision with the railing system at the extreme event limit state. The fatigue limit state does not need to be investigated for concrete deck slabs used in multi-girder bridges.

The AASHTO LRFD (7th Edition, 2014) provides two methods for deck design: The Traditional Design Method and the Empirical Design Method. The traditional design method can typically be employed in any situation, while the empirical design method has limitations based on deck geometry and bridge behavior. Additionally, a bridge owner may explicitly specify which design method shall be used by the designer.

The AASHTO LRFD (7th Edition, 2014) requires that the minimum thickness of concrete deck, excluding any provisions for grinding, grooving, or sacrificial wearing surface, should not be less than 7 inches. Thinner decks may be acceptable, only if approved by the bridge owner. For concrete deck slabs with a thickness less than 1/20 of the design span, consideration should be given to the use of prestressing steel in the direction of that span in order to control cracking.