NO. 6 BRIDGE: I-91 Rockingham Bridges

Looking at Vermont’s first four-span spliced precast concrete girder structure

(This feature published as "One of a Kind" in November/December 2021 issue)

December 02, 2021 / 1 minute read
NO. 6 BRIDGE: I-91 Rockingham Bridges

The new I-91 Rockingham Bridges are Vermont’s first four-span spliced precast concrete girder structure and is the last of three major bridge replacements on I-91 in southeastern Vermont.

The design-build project uses one-of-a-kind elements and some of Vermont’s largest precast segments, raised with massive cranes, to expedite and simplify construction while overcoming a unique unbalanced layout. The team constructed the wider, safer bridge atop a challenging topography and more than 130 ft above an environmentally critical river.

HDR’s team evaluated several bridge types. Converting the original concept to twin 852-ft-long, four-span bridges with precast, pre-stressed concrete and post-tensioned bulb tee girders, the haunched, spliced structure was the most efficient and cost-effective.

The new structure consists of five runs of seven individual concrete beams—weighing up to 93 tons each, installed on temporary framework, aligned and temporarily held in position with 30 steel strongbacks. The ends of the beams were tied together with cast-in-place concrete closures. In the end, the team installed, tensioned, and grouted three 19-strand tendons in each girder.

A unique aspect of the bridges’ design are their unbalanced spans, ranging from 167 to 245 ft. The unbalanced spans allowed the team to use the existing piers as temporary supports while erecting the structures’ haunched girders.

The new bridges were designed for a 100-year service life, 25 years longer than standard for other bridges in the area. To accomplish this, designers used stainless steel reinforcing, as well as high-performance, 9,000 psi concrete that is highly resistant to chloride penetration.

The concrete girder segments, 96 to 147.5 ft in length, vary in depth from 6 to 10 ft, and weigh up to 187,000 lb. The structure includes piers varying in height from 70 to 138 ft tall.

Project: I-91 Rockingham Bridges

Location: Rockingham, Vermont

Owners: Vermont Department of Transportation

Designer: HDR

Contractor: Reed & Reed

Cost: $50 million

Length: 852 ft

Completion Date: Oct. 1, 2021

About the Author

Related Articles

Louisiana state Department of Transportation and Development (DOTD) officials hope to cut the number of prospective sites for a new Mississippi River…
May 24, 2022
The Wyoming Department of Transportation (WYDOT) was awarded a 2022 Environmental Excellence Award (EEA) in the category of Ecosystems, Habitat, and…
May 20, 2022
State officials across Wyoming are preparing for an influx of federal funding from the Infrastructure Investment and Jobs Act. The more than $1.2…
May 19, 2022
Ohio lawmakers passed legislation this week approving nearly $700 million in federal transportation funding from the Bipartisan Infrastructure Law…
May 19, 2022