Cianbro Corp. of Pittsfield, Maine was awarded a $60 Million project to replace a 90-year-old Strauss heel trunnion bascule bridge in New London, Connecticut.
Cianbro wanted to use previously purchased Flexifloat barges to float the new 188-foot span between the existing piers and elevate it into place using an on-board jacking system. In addition to the weight of the span, the barge needed to accommodate the necessary substructure as well as jacking system. Finally, as the existing piers were being used to support the new span, Cianbro needed a barge that would both fit between the 150-foot gap between the pier fenders and also allow the contractor to safely perform the work.
Working with application engineers at Robishaw Engineering, Cianbro was able to configure their Flexifloats into a 140-foot-wide, 15,600-square-foot assembly to support the 3.2-million-pound deck load. A combination of timber mats and W36 beams was used to help distribute the load, keeping the deck bearing pressure within the rated 5,000 psf.
After the replacement span was erected on the Flexifloat barge, it was lifted approximately 35 feet above the water using strand jacks. The assembly was then positioned between the piers and the span was lowered onto the abutments. Despite several unprecedented operational challenges, Cianbro and Amtrak worked together to resolve these issues and restore full service as quickly as possible.
