EXODERMIC™ BRIDGE DECK DESIGN — AN OVERVIEW

An Exodermic™ (or “composite, unfilled steel grid”) deck is comprised of a reinforced concrete slab on top of, and composite with, an unfilled steel grid. This maximizes the use of the compressive strength of concrete and the tensile strength of steel. Horizontal shear transfer is developed through the partial embedment in the concrete of the top portion of the main bars which are punched with 3/4" holes.

Using standard components, the system properties and span capacities are generated and can be obtained from the Deck Properties & Spans table. Through the use of larger main bars and/or thicker concrete slabs, longer span capabilities can be achieved. Decreasing cover over the rebar will reduce the deck thickness if required for existing site conditions and reduce the weight of the deck as well. Further weight savings are possible using a lightweight concrete mix.

The concrete component of an Exodermic™ deck can be precast before the panels are placed on the bridge, or cast-in-place. Where the concrete is cast-in-place, the steel grid component acts as a form, the strength of which permits elimination of the bottom half of a standard reinforced concrete slab.

Exodermic™ decks are made composite with the steel superstructure by welding headed studs to stringers, floor beams, and main girders as appropriate, and embedding these headed studs in full depth concrete. This area is poured at the same time as the reinforced concrete deck when the deck is cast-in-place, or separately when the deck is precast. Exodermic™ decks require no field welding other than that required for the placement (with an automatic tool) of the headed shear studs.