Roslyn Viaduct

Location:

Nassau County, NY
 

Owner:

New York Department of Transportation, NY
 

Engineer:

Hardesty & Hanover LLP, New York, NY
 

Contractor:

Tully Construction Co., Flushing, NY
 

Contractor Construction Engineer:

Weidlinger Associates Inc., Mountain Lakes, NJ
and HDR Inc., Newark, NJ
 

Construction Inspection:

STV Inc. / PB Americas Inc. (Joint Venture), New York, NY
 

Constructability Reviews:

FIGG Bridge Engineers Inc., Exton, PA
 

Project Scope

Length:

• 2,200-ft long viaduct
• 2,775-ft (approach roadway, ramps and interchanges)
 

Cost:

$127 million
 

Awards:

"Top 10 Bridges in North America" in 2007 by Roads & Bridges magazine.
 

Resources

 
 
 
 
 
 
Roslyn Viaduct
Roslyn Viaduct
Roslyn Viaduct
Roslyn Viaduct
 
 
 
 
 
 
 
 
 
 
 
 
 

Design Challenge:
To replace a key bridge over Hempstead Harbor in Roslyn. The original steel superstructure of the Roslyn Viaduct opened in 1949 with two lanes of traffic in each direction. Today, it carries approximately 38,000 cars and trucks each day. This aging bridge had deteriorated and needed to be replaced with a modern, sustainable bridge.

Design Solution:
A precast, prestressed, variable depth, concrete segmental structure was the chosen technology for the new viaduct. This is Long Island’s first precast concrete segmental bridge. Several factors went into the decision making process, including a streamlined construction timeline by using pieces that are all cast offsite and the service life of a precast concrete bridge, which is targeted to be 60 to 100 years. Bayshore Concrete Products Corporation (BCP) located in Cape Charles, VA, was contracted to produce all 348 superstructure segments and 64 pier box column segments.

The twin structures of the new bridge will each have nine spans and eight pier columns with each structure carrying the traffic in one direction. The span lengths vary from 121 to 292 ft (36.9 to 89.0 m) and thus, the radius of curvature of the bottom of each span varies. As a result, each segment is unique. The 64 pier columns segments have a ship-lap architectural profile achieved by using formliners.

The majority of the precast concrete girder segments for the northern portion of the bridge were installed using a 700-ft-long gantry built on the site away from locations where it would impact travel. The northern approach roadways were completed first, in the fall of 2008. Once the northern half of the new bridge was finished, traffic switched to this new structure and the gantry shifted to the south to facilitate demolition of the southern portion of the existing structure. Construction on that portion then commenced. Self-consolidating concrete was used for cast-in-place closure placements, using a similar concrete mix to the one used for the column and girder segments.

Design Addresses Key Challenges
A key challenge focused on the soil conditions at the site, which were of varying compositions, with layers of organic material at some strata levels. There also is high groundwater that had to be considered in the design. Drilled and grouted micropiles were used to transfer the high dead loads into the ground. Drilling the piles rather than driving them also minimized vibration to nearby historic buildings and structures and to several 100-year-old wells in close proximity. Vibration monitoring was provided throughout the site.

Another significant challenge arose with transporting the precast concrete segments to the site. The largest segments weighed close to 100 tons. Initially, the construction team planned to use the channel waterway, but the NYS Department of Environmental Conservation was concerned about protecting the aquatic natural habitat. Instead, the segments were barged from the precaster’s plant in Cape Charles, Va., to a location several miles from the project and then hauled by specialized trailers to the site via ground-surface transportation routes. This approach required numerous contacts and discussions with local public agencies, residents and other stakeholders. The contractor obtained permits to use special multi-axle trailers to transport many of the bridge segments over the existing viaduct bridge.

Demolition of the existing bridge and construction of the new structure were coordinated to minimize traffic disruptions and required construction in two stages. Demolition of the northern third of the bridge came first. Then, new pier-column segments were installed and girder segments for the portion of the bridge east of the waterway erected. The column segments and many of the girder segments for the portion west of the waterway were transported over the existing viaduct during nighttime operations while the bridge was closed to traffic.

 
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