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Lift preparations were still underway at press time yesterday in anticipation of “strand-jacking” the first truss section of the new Milton-Madison Bridge into place onto temporary piers.
The procedure began early Monday when with the assistance of several tug boats, the 600-foot span, which was constructed on barges, was floated from the Milton shoreline into position at the base of the temporary piers.
In a media advisory, bridge officials had said the dates and times of the lift were subject to change. The operation was expected to transition very slowly over a period of several days, a Milton-Madison Bridge Project spokesperson said.
The bridge has remained open to traffic during the float and lift preparation procedures, and is expected to remain open for the duration of the lift operation. Spectators lined Vaughn Drive along Madison’s riverfront to watch the spectacle Monday and Tuesday. Recreational boaters were discouraged from watching the lift from the river. Boaters were to keep a distance of at least 500 feet on both the upstream and downstream sides of the bridge. Personnel from the U.S. Coast Guard were on the scene to enforce the restricted area. Additionally, a “no wake” zone for boaters was established 1,000 feet upstream and downstream of the bridge during the lift.
With the help of special hydraulic jacks and the expertise of an international firm, the first preassembled section of the new bridge - roughly the size of two football fields - was floated into place on barges in preparation for the 85-feet lift onto temporary piers. The method, called “strand jacking,” is designed to move heavy structures using bundled strands of steel cable.
In order to ensure a safe and efficient operation, project contractor Walsh Construction Company is using consultant VSL International to lift the 1,776-ton span.
“It’s where we take very large steel strands—they sort of look like a cable but they’re not a cable—and using hydraulic jacks that are capable of lifting heavy loads, the jacks, which will be up on top of the towers, will use the strands to lift that truss section up above the temporary towers,” Charlie Gannon, Walsh Construction Company project manager, explained.
“After the truss has reached the full height of the lift, a massive, 125-ton beam, called a ‘sliding girder,’ will be slid under the truss, supported by the temporary pier and a specially designed concrete pedestal on the existing piers,” Gannon said. “Eventually, this beam will be used for sliding the new 2,400-foot bridge from the temporary piers to the permanent piers, which are being rehabilitated and strengthened.”
“We’re frequently asked why we’re building the bridge in such a complex manner,” says Kevin Hetrick, Indiana Department of Transportation project manager. “This unique replacement method allows us to keep the bridge open during construction and keep traffic moving.”
While lift preparations for the first section of the new bridge is underway, workers continue to assemble the next span section – a 720-foot long truss that will be lifted into place in August using the same lifting method. The remainder of the bridge will be “stick built,” meaning it will be assembled in place using cranes.
“Eventually there will be two bridges sitting side-by-side, about 15 feet apart,” Project Manager Dav Kessinger with the Kentucky Transportation Cabinet, explained. “Then, later this year, we’ll divert traffic onto the new bridge on temporary piers. That gives us time to dismantle the existing truss and get ready for the slide.”
Replacement of the narrow and deteriorating 1929 bridge - a joint effort by INDOT and KYTC - began in early 2011 and is scheduled to be complete in 2013. Because the existing piers are being reused, the new wider bridge will lie within the footprint of the existing bridge.