"This is the kind of transportation project we like to see: planned with community input, utilizing effective accelerated construction techniques, and, as a result, completed significantly ahead of schedule.”

Governor
Lincoln D. Chaffe

 

Best Rehabilitated Bridge

Stillwater Viaduct in Smithfield, R.I.

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The Stillwater Viaduct over the Woonasquatucket River in Smithfield, R.I., is a landmark celebrating one of the state’s early attempts to accommodate the automobile age through highway infrastructure. The bridge is eligible for listing on the National Register of Historic Places, both for its historical association with the massive bridge building campaign in the 1920s and 1930s and for serving as an important local example of an open spandrel arch bridge.

When it was rehabilitated in 2012, designers had to be careful to maintain the original design aesthetics. “Maintaining the look of the old bridge was very important to the owner,” says Bharat Patel, Vanasse Hangen Brustlin’s engineer of record for the project. A precast concrete design allowed the team to seamlessly replicate the original features of the architecturally significant bridge with a high-performance solution that will stand the test of time.

The use of precast concrete was also critical to completing the project within the very limited schedule established by the owner. “Instead of constructing the bridge in phases over three-years, RIDOT promised the community it would be reopened in one season,” Patel says. “Using precast concrete components allowed the construction schedule to be accelerated to meet that goal.”

The team replaced the severely deteriorated superstructure with precast concrete stringers, pier caps, floor, and spandrel beams at the arch span, as well as fascia beams with cantilevered brackets and decorative bridge rail with spindles. The bridge deck is 8 in. (200 mm) thick cast-in-place concrete with a waterproofing membrane followed by a 3 in. (75 mm) asphalt overlay. All of the precast concrete was pigmented to match the old structure.

The existing arch rings and pier columns were also restored during construction, which included patch renovating arch ribs and pier columns, partially replacing tops of existing pier columns, crack sealing, and fiber wrapping arch ribs to improve seismic performance.

“One of the major accomplishments on the project was the production, shipping, and erection of the slender precast beams,” says Bob Slaw, president of Slaw Precast in Lehighton, Pa. To control cracking and increase stiffness of the longer units during shipping and erection, high-strength concrete in excess of 8000 psi (55 MPa) was utilized and prestressed strands were added. A temporary steel wide-flange beam, acting as a braced spreader for erection, was dowelled into the top of the longer units during shipping. Once at the site, the contractor erected the beams with tandem picks, with pick distance in excess of 200 ft (60 m), relying on strategic crane placement to put the beams in place.

Despite the massive rework and short time frame, the bridge was substantially completed in just seven months and reopened to traffic one month ahead of schedule. “We were able to stay way ahead of schedule without compromising quality,” Patel says, “and everyone in the community was pleased with the results.”

Slaw says that the use of precast concrete to create the slender beam design and interesting details resulted in a beautiful and elegant bridge that still fit the budget. “It proves you don’t have to spend a lot of extra money to get a bridge that is attractive and will last for a very long time.”

PHOTO CREDIT

Mark Flannery Photography, Northern Construction Services

PROJECT CREDITS

Owner: Rhode Island Department of Transportation, Providence, R.I.
Engineer of Record: Vanasse Hangen Brustlin Inc., Providence, R.I.
Precaster: Slaw Precast, Lehighton, Pa.
Precast Concrete Specialty Engineer: Eriksson Technologies Inc., Temple Terrace, Fla.
Contractor: Northern Construction Services LLC, Weymouth, Mass.
Project Cost: $9.5 million