A Jane Addams Memorial Tollway (Interstate 90) contractor has completed the first phase of prestressed concrete erection for the $95 million Fox River Bridge expansion—24 bulb tee girders, 90-in. deep, 150- to 168.5-ft. long—proving how a proprietary hoisting scheme can replace conventional crane picks without disrupting immediately adjacent highway traffic.
Wisconsin heavy/civil contractor Edward Kraemer & Sons Inc. devised twin gantries, each with a) one leg bearing on an existing structure of concrete deck, legacy prestressed concrete I girder and conventional cast-in-place pier design; b) the other leg mounted on newly cast piers widening the Fox River/I-90 crossing from six to eight lanes. For the Elgin, Ill., project’s first new girder phase, Kraemer crews positioned the 80-ft. long, 11-ft. wide and 27-ft. tall gantries 150–170 feet apart, depending on beam length.
Each frame is designed with an 11-ft., cross-braced column on both ends to bear overhead trusses carrying two, 50-ton hoists and trolley. The gantries hoisted the deep bulb tees from trailers loaded at the new County Materials Corp. precast/prestressed operation in Janesville, Wis. The producer’s contract covers 144 beams; over 2014-2016 phases, they will be placed in four 170-ft., two 150-ft. and two 164-ft. spans—nine girders across each of two structures.
Once phase one beams were set, Kraemer crews disassembled the gantry frame and moved it to the next open pier. They continued the sequence across seven piers serving new eastbound lanes and will repeat the process in mid-2015 for westbound lanes bearing on new cast-in-place piers. A 2014-16 window will see a new Fox River Bridge engulf the original structure, whose demolition is phased such that three lanes of traffic in each direction can be maintained nearly 100 percent of the time.
All initial girder erection work proceeded without having to close any I-90 lanes, a convenience cranes staged on the existing bridge would not have afforded. Kraemer positioned a standard height concrete barrier to separate eastbound traffic—flowing at or near normal speed—from the gantry, trailer and girder staging area.
In addition to speedy beam placement, the gantry scheme enables Kraemer to deliver the new Fox River Bridge with a single longitudinal joint versus three on the original structure. Such streamlining is a critical engineering detail for Illinois Tollway, an agency wise to maintenance costs and traffic disruption attributable to continuous bridge deck openings. Elimination of two longitudinal joints will net an incentive for Kraemer, which is handling abutment-to-abutment work as a member of lead contractor, Kenney Kraemer Joint Venture. Illinois Tollway has engineered the project in house and retained Oak Park, Ill.-based Thomas Engineering Group as construction manager.
The new Fox River Bridge will have side-by-side 1,315-ft.-long structures rising 40 feet above the water and adjacent roadways. With eight spans and seven piers—versus the original structure’s 14 piers—each crossing will reduce the environmental impact on the waterway and forested fen below. Illinois Tollway is upgrading the bridge as part of the I-90 Rebuilding and Widening Project, scheduled for 2016 completion.