Liberty Bridge Exodermic Bridge Deck Panels
The Pennsylvania Department of Transportation announced a multi-year $80 million dollar project to replace the Liberty bridge deck with Exodermic® deck panels. An Exodermic, or composite, unfilled steel grid, bridge deck is comprised of a reinforced concrete slab on top and an unfilled steel grid. This efficient system maximizes the strength of the concrete and the tensile strength of steel to provide a lightweight, strong and durable bridge deck.
Due to the limited roadway width of the mainline portions of bridge spans 12-14, the Exodermic deck was installed with precast panels and an accelerated concrete mix for closure pours. Concrete Concepts ,Inc. precast 69 panels under controlled conditions at their McKees Rocks, PA facility using the layout design and shop drawings supplied by Delta Precast.
The deck replacement project capitalized on another advantage of grid reinforced concrete decks with its high strength-to-weight ratio. The Liberty Bridge had a load rating of 30 tons and was structurally deficient with major steel deterioration. This was corrected by maximizing the strength to weight ratio. Design engineers were able to increase the stringer spacing 9 ft. 9 in., and in some locations, increase its current load rating to 40 tons.