According to Vermont Agency of Transportation (VTrans), four multi-span bridges along the heavily traveled Interstate 89 corridor, were severely deteriorated and had earned a poor rating. The primary goal of the project was to extend the life of the heavily traveled bridges safely and economically.
Demolition and rehabilitation of each bridge was something that had to be carefully considered so as not to interrupt the public or impact the environment. The scope of work included deck replacement, steel repairs, and replacement of back-walls, approach slabs, and sleeper slabs.
The project achieved an accelerated project schedule through the use of Accelerated Bridge Construction (ABC) methods. The project was completed over several weekends and traffic was maintained by creating crossovers through the construction zone.
Precast concrete was immediately identified as a means to meet the goals of this compressed schedule. It allowed for quick construction which reduced the impact to the traveling public by limiting the project to six total weekend closures. Precast also provided a superior quality bridge deck.
A proprietary bridge deck system called AccelBridge™ was identified early in the planning and design process as a method to replace the bridge decks between the strict weekend time frames. This bridge deck system eliminated very expensive and timely closure pours between precast decks units.
Only one closure pour was required and all shear stud pockets had to be grouted. The precast panels were match cast in Fort Miller's production facility with interlocking shear keys to provide reliable shear transfer. The shear keys also self- align when being installed, thereby allowing for rapid field setting.
During the limited work hours, from 7pm Friday night to 6am Monday morning, the contractor, Kubricky Construction, installed the precast deck panels. The panels were compressed together by jacking against the girders on the bridge, thereby leaving the completed decks in compression and without cracks. This satisfied the goal of extending the life of the bridge decks by an estimated 40-years.
The Fort Miller Co., Inc. manufactured a total of 23,535 SF of bridge deck panels representing (58) panels, (32) precast concrete approach slabs, (8) precast concrete sleeper slabs, and (32) precast concrete back-walls for the project.
The four bridges each have three spans. Two of the bridges have a total span of 154-ft and cross over a local road and bicycle path. The remaining two bridges have a total span of 185-ft and are cross over an environmentally sensitive waterway.
The four bridge decks replaced over several weekends. For each weekend, the closures spanned from 7pm on Friday to 6am on Monday. Weekend one included demolition and replacement of back-walls and installation of sleeper slabs on Bridge 77N. Weekend two closure included demolition and replacement of existing bridge deck on Bridge 77N and performing back-wall and sleeper slab replacement on Bridge 76N. Weekend three closure included demolition and bridge deck replacement of Bridge 76N. The entire process was replicated for the two southbound bridges on three consecutive weekends.
It took just six weekends in total during the summer of 2019 to complete the entire project, including substructure and steel repairs. The design build team, including the owner, the EOR (engineer of record), general contractor, and the precast concrete manufacturer, worked together to complete the project successfully. That included meeting goals of improved constructability and safety, within the tight schedule and the $12.5M budget.