Hartford Lateral Slide Bridge

Located in Hartford, Vermont, the Hartford I-91 Improvement project replaced the north- and southbound bridges carrying Interstate 91 over US Route 5. The existing bridges with suspended-span steel connections were built in 1966, and were determined by the Vermont Agency of Transportation to be fracture critical, meaning that if one steel member of the bridge were to fail, a portion of or the entire bridge was likely to collapse. Both bridges needed to be replaced immediately, with limited inconvenience to travelers. 
PCL used the innovative accelerated bridge
construction method of a lateral slide to replace
fracture-critical bridges in Hartford, Vermont. 

A birds-eye view of the north- and southbound I-91
bridges sliding into place.​

Through the use of the innovative accelerated bridge construction method of a lateral bridge slide, PCL’s Transportation Infrastructure Group replaced the north- and southbound bridges and successfully completed Vermont’s first major lateral bridge slide. 

SLIDING TO SUCCESS 

With nearly 15,000 vehicles traveling over the north- and southbound bridges each day, it was essential that the project team limit the effects of construction on the traveling public. 

One of the Vermont Agency of Transportation’s goals was to replace the bridges during only two weekend closures of I-91, and with no full closures of US Route 5, thus allowing weekday travelers to keep to their regular routes. To meet this goal, PCL used the innovative accelerated bridge construction method of a lateral slide to replace the north and south bridges. Accelerated bridge construction shortens project schedules and significantly minimizes traveler inconvenience. 

To complete the replacement, the team first built the new superstructures adjacent to the existing bridges. The bridges remained open without the need for a long-term Interstate closure or detour. 

Once the existing bridges were demolished, the team used hydraulic jacks placed underneath the new bridges to push, or slide, each bridge into place over the course of two closure weekends. Without using this slide-in bridge technique, the project would have resulted in mobility impacts lasting upwards of six months. 

ACCELERATED EXPERIENCE 

For the project to be a success, the Vermont Agency of Transportation needed a contractor with experience in accelerated bridge construction methods—specifically with lateral slide bridges—who could be responsible for the design, construction, and overall performance of the bridges. 

PCL’s Transportation Infrastructure Group has extensive experience using accelerated bridge construction methods, including lateral slide bridge technique, to replace bridges. The lateral slide bridge method in combination with the construction manager / general contractor (CMGC) alternative delivery method enabled PCL to become involved in the project early on, during preconstruction. PCL’s preconstruction services on this project enabled the team to modify the design to accommodate constructability features for the lateral slide technique and improve the project’s schedule before construction began. 

Once the closure weekends ended, the Vermont Agency of Transportation surveyed local residents to ask their opinion about the bridge slides. Survey results showed that 100 percent of the respondents were satisfied with how the new bridges turned out, and 99 percent liked how the project was delivered, using accelerated bridge construction methods. The two bridges were completed ahead of schedule and are estimated to last, at a minimum, for the next 80 years. 
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