Davis Narrows Bridge

DESIGN CHALLENGE: Replace a deteriorated single-span bridge, built in 1941 of painted steel-rolled beams on dry-laid granite blocks, with a new design that eliminates tide constrictions and is sensitive to the river environment, which serves as the breeding ground for horseshoe crabs and as a natural fishing ground.

PRECAST SOLUTION: 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: four precast concrete abutments; four wing walls; eight precast, prestressed beams; and four approach slabs.

The existing abutments were retained, with the precast concrete versions placed 12 feet behind them. The integral abutments were supported on four piles driven into bedrock. The abutments consist of two precast center units and two precast extended wing-wall units that were post-tensioned 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.

The beams, weighing 44 tons apiece, were 89 feet long, 4 feet wide and 3 feet tall. Three were delivered each day, and they were post-tensioned transversely to act as a single unit. The use of precast, prestressed beams significantly reduced construction time, with more saved by not having to add a deck. The project was finished with only one month of road closure.

Judges' Comments: This all-precast concrete bridge-replacement project hits the mark aesthetically while overcoming some very stringent environmental constraints. Closure time was minimized, creating a successful project on all counts in a very short amount of time.

Project Details

City:

Brooksville-Penobscot
 

State:

ME
 

Precaster:

 

Owner:

Maine Department of Transportation,
Augusta, ME.
 

Designer:

Maine Department of Transportation,
Augusta, ME.
 

Engineer:

Main Department of Transportation, Augusta, ME
 

Contractor:

Reed & Reed Inc., Woolich, Me.
 

Total Length:

95.5 ft
 

Structural Precast Elements:

• 4 Precast abutments (2 at each end)
• 4 Precast wing walls (2 at each end)
• 4 Precast approach Slabs (2 at each end)
• 4 Precast abutments (2 at each end)
• 8 Precast, prestressed concrete box beams, BII-48
 

Awards:

2006 PCI Design Award for Best Bridge with Spans Between 65 feet and 135 feet
 

Resources

 
 
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