Challenge
Much of the set-up work could be performed ahead of the rail closure. Working at night, we used two diamond wire saws working simultaneously to cut the concrete piers. The wire saws were mounted on the pier footings, and a barge carried the power units for the saws. Diamond wire ran from the saws up to transition brackets welded onto the steel pier casings. At each transition bracket, the wire switched from vertical to horizontal to cut across the circular pier. Wire sawing crews setup the transition brackets working from a manlift on the barge.
The old 83′ long bridge had rested on two abutments and a center pier cap. The old bridge had been removed prior to the pier cap sawing operation. Once the old pier cap was cut and a crane removed it, Blattner could place the new 52 ton steel cross girder into position.
“We were very happy with Bluegrass’ work,” says Jason Zierden, field engineer for DH Blattner & Sons Inc, a general contractor from Avon, Minnesota. “I’d say Bluegrass was ahead of schedule with their work. “Everything had to be very precise, because we had a certain window of time during which we could close the railroad to trains.”
“The cut sections were 6 feet tall and weighed 37,000 pounds,” says Zierden. “The cuts were precise and smooth. We could easily place the steel girder across the piers to build the bridge back into place.”