Unfilled Metal Grid Deck Composite with Reinforced Concrete Slab

An unfilled metal grid deck composite with reinforced concrete slab consists of a reinforced concrete slab that is cast on top of an unfilled grid deck, and is made to be composite with the unfilled grid deck. An Exodermic^TM deck, shown in Figure 13, is a specific manufactured type of unfilled metal grid deck which is composite with a reinforced concrete slab. In this type of deck, WT sections are used as the primary members, spanning from the supporting components (girders, stringers, cross beams, etc.). Secondary members are perpendicular to and interlock with the WT sections. The secondary members support thin gage sheet metal, which in turn supports the wet concrete of the reinforced slab. Negative flexural capacity is provided by the mild reinforcement located within the concrete deck slab.

Composite action between the unfilled grid deck and the concrete slab must be provided by shear connectors or other means capable of resisting horizontal and vertical components of interface shears. Article 9.8.2.4.2 of the AASHTO LRFD (7th Edition, 2014) states that acceptable methods of shear connection include tertiary bars to which 0.5 inch diameter reinforcement or round studs have been welded, or the punching of holes at least 0.75 inch in size in the top portion of the main bars of the grid which are embedded in the reinforced concrete slab by a minimum of 1 inch. The steel decking should also be galvanized or painted to protect the steel members from corrosion.

These types of decks are often attached to the main supporting components by shear stud connectors. Shear studs are welded to the main supporting components and a haunch is provided so that the shear studs are completely encased in concrete.

This type of grid deck can be used where the distance between supports is greater than 10 feet. On rehabilitation projects, the use of this deck type may permit the removal of stringers between floor beams.