Crews floated in and jacked a 1,400-ton, 188-ft-long, 35-ft- wide vertical-lift span into an existing 1,400-ft alignment over the Thames River in Connecticut on June 24-27. Cianbro Corp. had only 96 hours to install the new Amtrak railroad span before reopening the route to 36 daily passenger trains.

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The new movable span replaces a 90-year-old Strauss heel trunnion bascule that tilted on bearings to open. “The bridge had a history of issues concerning its ability to open and close 1,600 times a year,” says James Richter, Amtrak deputy chief engineer for structures. “The trunion counterweight retainer bolts kept breaking.” The 2.5-in.-dia., 5-ft-long bolts had to be constantly replaced.

Moreover, the electrification of the railroad route in 1999 added several hundred thousand lb of dead load due to the overhead catenary system, contributing to the risk of the movable span getting stuck, Richter adds.

Amtrak

Amtrak A 90-year-old truss is replaced with a vertical-lift span.

Pittsfield, Maine-based Cianbro won the approximately $60-million contract in 2005 for the replacement span in New London, designed by HNTB Corp., Kansas City, Mo. The existing bridge piers, about 130 ft deep into sand and gravel, had to be expanded to support the new 200-ft-tall towers for the new vertical-lift span. To do that, crews installed four new 36-in.-dia. pipe piles down to bedrock, 180 ft deep.

Unexpected settlement and movement of the main pier up to 1.5 in. vertically and 4 in. laterally, however, “caused considerable grief,” says Richter. “If it were not a movable span, it would not have been such a big deal.”

Amtrak called in Mueser Rutledge Consulting Engineers, New York City, to investigate. “We had disturbed the boulder layer and caused sand and gravel to shift,” says Richter. Cianbro hired The Judy Co., Kansas City, Kan., to pump some 1 million gallons of special grout through tubes around the foundations. “We had as many as three drill rigs and three grout pumps,” says Chet Muckenhirn, Cianbro project manager. In addition to enlarging the piers with reinforced concrete, “we did post-tensioning that wasn’t originally anticipated.” That extra work added about $13 million and eight months to the job, notes Richter.

The challenges did not end there. The installation of the new span originally had been planned for mid-June. But the contractor had to scrap the initial plan to cut the old bridge’s 4-million-lb counterweight into five pieces with diamond-wire saws before removing them with a barge crane. The wire saws could not penetrate a section of steel punchings shaped like “doughnut holes” and filled with concrete, says Richter. So the contractor removed 1.5 million lb of concrete with hoe rams to lighten the counterweight enough so it could be cut free and temporarily supported on the existing trunion bearings.

The removal of the 650-ton span and new installation “went like clockwork,” says Cianbro Vice President Lincoln Denison. Crews used a 1,000-ton barge crane to lift out the old span. The new lift span was jacked up about 32 ft, then slid over and dropped 5 ft into place with 1⁄8-in. tolerances.

Shortly following the installation, crews made the new span operational for full 135-ft lifts, says Denison. Cianbro avoided the $500,000-per-day penalties that would have occurred after the four-day outage. “We will come in and keep removing the concrete down to the point where we can lift the ‘pork chops’ out,” says Denison, referring to the distinctive shapes of the main steel segments of the counterweight. This summer, Cianbro will finish building a protective fender system using recycled plastic and fiberglass reinforcing, says Richter.