By Mark Holan, editorial director, ARTBA
Crews are on target to complete the southbound span of the I-91 Rockingham Bridges project in Vermont by early summer, design-build engineer and ARTBA member firm HDR says.
The $50 million Vermont Agency of Transportation (VTrans) project, about 40 miles north of the Massachusetts state line, is replacing two spans built in the 1960s and known locally as the High Bridges. Work began in 2016, and the new northbound bridge opened to traffic in April 2019.
Advances in bridge barriers resulted in an 8 foot wider driving surface on each new bridge while only increasing the width of each by 6 feet. The new bridges will be four-span, spliced precast concrete girder structures — a first in Vermont.
Each bridge includes piers that vary in height from 70 to 138 feet tall. To accommodate VTrans’ stringent requirements for pier slenderness, HDR used two bearings per girder at each pier. This increased the rotational stiffness at the pier caps.
“This project was particularly challenging because of the need to balance the means and methods of our contracting partner against the contract slenderness requirements of the tall piers,” said Thomas French, HDR, PE, senior project manager.
“Adding to the technical challenges, the 862-foot-long bridges utilized unbalanced span lengths, which allowed us to use the existing piers as temporary supports during erection of its haunched girders,” French continued. “This also allowed us to clear the railroad and the river without significant impacts.”
Reed & Reed, Inc. of Woolwich, Maine is the contractor. Seven HDR offices and six sub-consulting firms worked to complete the design on time. See more details from HDR.