Owner: New York State Department of Transportation
Structural Engineer: New York State Office of Structures
Precast Supplier: The Fort Miller Co., Inc.
Lightweight Aggregate Producer: Norlite LLC
Contractor: The Lane Construction Corporation
The Thaddeus Kosciusko Bridge located in upstate New York, known locally as the Twin Bridges, is a pair of identical through arch bridges constructed of steel with concrete decking in 1959 that span the Mohawk River on Interstate 87 between exits seven and eight. The two bridges carry three northbound and three southbound lanes of traffic.
New York State Department of Transportation’s reinvestment in these bridges will increase their lifespan and save money by avoiding costly repairs in the future. The project was part of the NYSDOT’s Accelerated Bridge Construction Program that minimizes impacts to traffic by utilizing the weekends for lane closures. The northbound bridge deck was removed and replaced over seven weekends in the fall of 2012 and the southbound bridge deck was removed and replaced over five weekends in the spring of 2013.
The New York State Office of Structures specified lightweight precast pieces to increase the load ratings of the refurbished structures.
The Fort Miller Co., Inc. cast a total of 236 precast pieces of which 12 were precast approach slabs. Ira Adler of Fort Miller developed a high performance lightweight concrete mix design in accordance with the guidelines set forth by NYSDOT. The lightweight concrete mix design achieved release strengths of 4000 psi within 18 hours with an average 28-day strength in excess of 7000 psi. The specified lightweight concrete equilibrium density was 115 pounds per cubic foot.
The lightweight precast pieces had a 26% reduction in weight per piece that in turn helped with the sizing of the mobile crane.
The closure placements between the precast pieces utilized a high performance rapid set concrete capable of achieving 3000 psi in less than three hours connecting the precast deck and barrier pieces. An asphalt overlay was applied as the final wearing surface.
