Heavy Crossing in Connecticut is Looking Up After Rough Start.

05/27/2002
Engineering News-Record
17
(Copyright 2002 McGraw-Hill, Inc.)

ONE OF THE HEFTIEST LIFT span bridges in the U.S. is on track for an August completion despite a rocky past. Cianbro Corp. is floating, digging, lifting and bolting New Haven, Conn.'s heavy Tomlinson Bridge over the Quinnipiac River at a swift pace.

Erection of the $95-million span stalled when the original contractor, White Oak Corp., Plainville, Conn., went bankrupt. ``The job started in 1994 and was to end in 1998,'' notes Steve DiGiovanna, project manager for the Connecticut Dept. of Transportation. But when Cianbro restarted work on the 900-ft crossing under a revised schedule in 1999, it had less than two years to do more than 60% of the job, says Bob Pellerin, superintendent for the Pittsfield, Maine-based contractor.

Engineers at Hardesty and Hanover, LLP, New York City, say that the lift span has to accommodate different loads from the rail line and highway. The legacy of previous bridges at the site--most recently a movable bascule bridge built a half-century ago--increased Cianbro's contract from $87.8 million to $996 million, says DiGiovanna. Demolition crews encountered "a lot of large types of granite from old construction and timber matting,'' he says. "There were increased costs for disposal of controlled materials, contaminated soils and groundwater during excavation.'' During construction, traffic moved over a temporary movable bridge, supplied by Acrow Corp., Carlstadt, N.J.

Caisson depths range from 50 to 120 ft deep on the west side, where the bedrock is deeper and steeper, notes DiGiovanna. Approach spans are supported on H-piles driven about 100 ft deep. For lift piers and for substructure on the east side, 30-in.-dia caissons are socketed into rock 15 to 40 ft deep.

Each 150-ft-tall tower has four 20-ft-dia sheaves, 85 tons apiece. Cianbro used 100-ton jacks to pull the front columns inward to create an outward bow needed to bolt up the transverse sheave girder utilizing camber, says Pellerin. Counterweights of 3 million lb are hung 113 ft above the roadway from the sheave girder to offset the 6-million-lb span.

Six of 11 cranes worked off a 140-ft x 220-ft barge with a 13-ft-high truss to support the span from beneath. Crews erected the lift span portion adjacent to the site. Once completed, it was floated into place and attached over a five-day period. Crews also worked on a floating walkway hanging off temporary sheet pile below the bridge. This increased safety from traffic and "gives us access to every pier out there,'' says Pellerin.