The I-91 Brattleboro Bridge Improvements Project, designed by GM2's Complex Bridge staff, includes the demolition of four existing bridges between Exits 2 and 3 and replacing the four bridges with new structures. New Bridge 8 carries I-91 over a local road using NEXT Beams. New Bridge 9 is a 3-span, 1,036-foot arching concrete bridge over the West River built utilizing balanced cantilever construction. Standing 100 feet above the scenic valley, the 515-foot main span forms an open gateway anchored by curving, cathedral piers. This postcard worthy bridge features viewing platforms for pedestrians, hikers and visitors at the base of each pier overlooking the West River and mountainous valley. True to its theme “A Bridge to Nature,” every detail of the uniquely-shaped superstructure, piers, viewing platforms, and the railings are complementary of the natural landscape. The concrete cantilever construction process off ered minimum impact when crossing busy Vermont Route 30, the West River, and popular West River Trail.

A Visual Quality Advisory Team consisting of VTrans, local Aesthetic Committee members, and GM2's Complex Bridge staff selected eco-friendly concrete stain colors, platform railing designs, and other aesthetic details. GM2's Complex Bridge staff designed the replacement bridges and provided design support and on-site construction engineering services to the contractor during construction.

Long, arching spans and tall, slender piers create an elegant concrete structure across the Monongahela River. This 3,200’ long bridge consists of seven spans, including a 518’ main span, built using balanced cantilever segmental construction to cross the river, two active rail lines and local roads. Cast-in-place concrete construction was used to form the 89’ wide, dual-cell box girders in this mountainous terrain where piers reach over 200’. The bridge includes over seven million pounds of reinforcing steel, 3,324 linear feet of drilled shafts, 51 thousand cubic yards of concrete and three million pounds of post-tensioning. The impact of tall piers, limited access, and river, road, and railroad crossings on the construction was minimized by using balanced cantilever concrete segmental construction.

GM2’s Complex Bridge staff worked with the contractor to provide a Contractor Alternate Design-Build solution that was bid competitively against an owner’s as-designed project. The Contractor Alternate design resulted in significant savings for the Pennsylvania Turnpike Commission over a steel plate-girder design. The contractor’s low bid of $95 million, which included design costs, was $8.6 million less than the price bid for the owner’s as-designed structural steel bridge contract documents.

The bridge was opened to traffic in July 2012. GM2’s Complex Bridge staff provided on-site construction engineering and inspection services during critical construction activities and provided home office support and construction engineering to the contractor.

GM2's Complex Bridge staff provided the design for this bridge, which opened to traffic 42 months after Maine DOT identified the emergency replacement need.

The cable-stayed system is state-of-the-art and includes cradles to carry the stays through the pylon, eliminating the need for pylon anchorages; a pressurized inert gas system to protect the strands and a force monitoring system that tracks important information about the stays throughout the bridge’s projected 125 year service life. After the bridge opened to traffic in late 2006, six reference strands were removed and replaced with carbon fiber composite strands, a first in the United States. Monitoring of all strands in the bridge will evaluate carbon fiber for future bridge uses.

The theme of “Granite-Simple & Elegant” was chosen to honor the long time granite quarrying industry located close to the bridge site. The bridge location, adjacent to historic Fort Knox, inspired a connection to the Washington Monument and resulted in obelisk-shaped pylons. Significant coordination and planning with the Maine Historic Preservation Commission to preserve the historical nature of adjacent Fort Knox. The three-story observatory at the top of the pylon on the Waldo County shoreline welcomed 72,000 visitors in it’s first season.