Davis Narrows Bridge

The new bridge replaced a deteriorated single-span bridge, built in 1941 of painted steel-rolled beams on dry-laid granite blocks.

The new design eliminated tide constrictions and is sensitive to the river environment, which serves as the breeding ground for Horseshoe crabs and as a natural fishing ground.

After examining options, the design team quickly decided that an all-precast concrete system could provide rapid construction while addressing the issues at the site and opening the road to traffic in the shortest time.

The bridge consists of:
4 precast concrete abutments4 precast concrete wing walls8 precast, prestressed concrete box girders4 precast concrete approach slabs.

The existing abutments were retained, with the precast concrete versions placed 3.6 m (12 ft) behind them.

Abutments and wing walls

The integral abutments were supported on four piles driven to bedrock.

The abutments consist of two precast center units and two precast extended wing-wall units.

Abutment and wing wall components were post-tensioned together with six threaded bars.

 Voids were designed into the abutments to receive the piles.

Once the abutments were post-tensioned, the voids were filled with self-consolidating concrete.

Box girders

Three girders were delivered each day.

The 8 box girders, weighing 45 t each, were 27.1 m (89 ft) long, 1220 mm (4 ft) wide and 915 mm (3 ft) tall.

Girders were post-tensioned transversely to act as a single unit.

Joints between girders were grouted prior to the final lateral post-tensioning.

The use of precast, prestressed beams significantly reduced construction time, with more time saved by not having to add a deck.

Approach slabs

Wing wall and guardrails in place

Bridge deck membrane

Bridge deck paving

FAST BRIDGE CONSTRUCTION
The project was finished with only one month of road closure.

Designer/Owner: Maine Department of Transportation, Augusta, Maine
General Contractor: Reed & Reed Inc., Woolich, Maine
Precaster: Strescon Limited, Saint John, NB, Canada

 
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