Rockingham bridge replacement ends on time: CEG

Every piece of precast concrete from the delivery trucks had to be removed from the existing bridge.

When the Vermont Transportation Agency (VTrans) replaced two old bridges on I-91 in the town of Rockingham, spanning the Green Mountain and Williams River railroad track, it did so with precast girder bridges.

Reed & Reed Inc. The $44.3 million design-build project last September, after it was notified to proceed in July 2016 and design-build was authorized in February 2017. The bridge is located in southeastern Vermont in the heart of the Green Mountains.

“The motorway crosses a middle valley in Rockingham,” according to VTrans. “Precast split girder bridges exceeded the 100-year service life requirements for bridges and are the first bridges of this type in Vermont. The design provided an economical solution to this important transmission link: an all-concrete structure comprising prestressing, post-tensioning and a mixture of reinforcement materials, allowing to local suppliers by providing the necessary materials and providing the required service life of 100 years, in an aggressive defrosting environment.”

The new bridges, the longest precast truss bridges in the state, were built on the same site as the 736-foot-long, nearly 35-foot-wide double steel truss bridges built in 1965. They are built over challenging terrain 130 feet high over an ecologically critical river.

“Although the bridges were rehabilitated in 1989 to provide additional skeletal life, they continued to deteriorate,” VTrans told CEG. “The width of the bridge also does not meet current standards. They were considered critical bridge fractures and were not well loaded. Planning began in 2013 when a scoping report with alternatives was completed and a decision was made to replace the structure with a new bridge considered the best solution.”

This is an important highway for Green Mountain State.

“I-91 connects Massachusetts to the Canadian border and it is critical that its condition serves travelers as they commute to work, vacation, and transport goods and services into and out of our state,” VTrans said. “It also connects to I-89 and many state highways that cross the Connecticut River and serve New Hampshire residents. Rockingham bridges must be replaced in order to maintain our network and ensure that travel on our highway is safe and efficient.”

Several local figures noted “the positive economic benefit of a project of this size in a small community. The infrastructure is improved, and the local economy is stimulated by the influx of people living and spending money in the community.”

To match the current interstate lane, each bridge has two 12-foot-wide lanes, one of which is 10-foot. 4-foot single shoulder collapse. Medium shoulder. Each new bridge is more than 41 feet wide and 18 percent wider (more than 6 feet) than previous bridges and spans 860 feet from stanchion to stanchion, which is 110 feet longer than previous bridges. HDR Inc. Bridges are designed.

Until replacement, the old bridges were open to traffic. The old bridges were demolished before the new bridges were installed.

“Every piece of precast concrete had to be taken out of the delivery trucks from the existing bridge,” VTrans said. “The contractor deployed a rolling roadblock that slowed interstate traffic to create a 20-minute window to connect and stabilize the part. The northbound bridge opened to traffic in April 2019, and the south bridge fully opened in September 2021. The public watched the project with enthusiasm and wonder due to the scale of the elements and the relatively low impact of the project on the daily lives of local residents and passengers.”

Reed and Reed had to overcome many challenges to complete the project.

“The project was 100 feet off the ground,” said John Phillips, R&R project manager. “All heavy lifts were executed at a great height with the lowest clearance between the two bridges. Extensive structural engineering was carried out to ensure the project was carried out safely. Work had to progress in a systematic process in order to maintain safety and efficiency. The design and build process allowed us to start work while completing Design and layout as we go along.

“We have built large prefabricated and sectional bridges in the past,” he added. “This design was unique in that we had concrete girders with mid-span joints at great height with difficult access. Environmental concerns are always at the forefront of our work planning. We had to mitigate interference with the flow going through the project’s primary access.”

The finished parts were manufactured by JP Carrara of Middlebury, Vt. , which was manufactured over a period of 17 months. The beams were nearly 200,000 pounds, and over 100 feet long.

“The concrete girders were made of steel reinforcement, pre-tensioned threads and a post-tensioning system installed on site,” Phillips said.

It took JP Carrara between six and eight hours to get the pieces they produced to the job site.

The northbound bridge was installed in April with girder sections raised and laid using a Manitowoc 16000 crawler crane and a Model 999 Series.

“We generally pitched the girders from north to south,” Phillips said. “The parts were lifted from the trucks in about 20 minutes to allow highway traffic to resume. However, it took a few hours to get the girder installed and fully secured.”

The beams and other components were lifted mainly during the day.

“We also have various support cranes on site, as well as all-terrain forklifts and a boom truck,” he said.

The demolition of the old bridges caused crews to move all the spans and cut the steel trusses that were sent for recycling.

“One of the challenges was getting the distances to the ground where it could be chipped,” Phillips said. “This requires extensive structural engineering and planning.”

A rigging system was installed to prevent any debris from falling into the river and onto the railway tracks.

After installing one bridge, the crew was able to apply the lessons learned to the southbound bridge.

“Advance planning has helped somewhat, but there are always unexpected challenges with construction projects,” Phillips said.

The management team included R&R management, supervision and HDR design professionals.

“The design and construction team worked continuously as one to deliver this project safely and to the highest quality,” said Phillips. “The crews work tirelessly and have been dedicated.”

R&R had other standard pieces of equipment on site.

“We had mechanics on site at times primarily if equipment issues were likely to cause safety or other impacts on public travel,” Phillips said. “During the winter we constantly had to deal with road salt and sand falling off the highway. This created erosion issues that had to be watched for.” CEG

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