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  • Sverdrup Civil, Inc., of St. Louis found it necessary to reduce the dead load of the highway deck. This was accomplished by the use of simplified structural framing supporting an Exodermic bridge deck.

Analysis of the arch truss spans determined that the superstructure dead load had to be limited to 116 psf (5.6x10-3 MPa) in order to carry 4 lanes of HS-20 loading. The previous framing system for the deck consisted of floor beams at approximately 6 foot (1.8 meter) spacing. The efficiency of the Exodermic deck allowed the number of floor beams to be reduced by half. The new floor system framing consists of fabricated floor beams at 12 foot (3.7 meter) centers, with the Exodermic deck spanning across the floor beams in the direction of traffic, without stringers.

Following extensive work on the approaches, contractor St. Louis Bridge began to install Exodermic panels in the summer of 2001. Contractor St. Louis Bridge purchased heavy duty crane mats in order to move their cranes, equip- ment, and construction materials out on the bridge. The work sequence included setting new floor beams and miscella- neous additional steel members. Deck

Bridge deck was fabricated in three span continuous panels, spanning twelve feet floor beam to floor beam without stringers

work was divided into longitudinal stages for ease of access. The grid panels for the Exodermic deck were set using a light crane, picking panels from a light trailer pulled by a pick-up truck. With the crane mats in place, it was possible for concrete trucks to drive right out to the work zone and place the concrete

deck. Once the deck on one side of a span was complete, that side could be used as the platform for placing the other side, and the crane mats moved on to the next span.

Deck work is scheduled to be com- pleted this year.

directly for the cast-in-place Exodermic

Exodermic Design

An Exodermic bridge deck, or "unfilled grid deck compos- ite with reinforced concrete slab" (AASHTO LRFD) utilizes both a fabricated steel grid (the bottom portion) and a reinforced concrete slab (the upper portion).

CONCRETE (CAST-IN-PLACE SHOWN; MAY BE PRECAST)

GALVANIZED FORM PAN

The top portion of the main bearing bars of the steel grid extend upward into the reinforced concrete component and act as shear connectors, assuring internal composite behavior.

Advantages of this design include light weight, rapid construction, and efficiency of overall structural design.

CONCRETE HAUNCH (POURED SEPARATELY WITH PRECAST PANELS)

MAIN BEARING BAR

DISTRIBUTION BAR

VERTICAL BULKHEAD

EXODERMIC BRIDGE DECK, INC. • 60 LONG POND RD, LAKEVILLE, CT 06039 • TEL: 860.435.0300 • FAX: 860.435.4868 • info@exodermic.com

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