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Many steps remain in bridge construction

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By Dave Taylor

“It’s beginning to look like a full-length truss bridge now, which a lot of people will think that sort of signifies the bridge being complete but there’s still work to be done.”

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That was the recent assessment of the progress of the Milton-Madison Bridge Project by Aaron Stover, an engineer with Michael Baker, Jr., Inc., the company in charge of bridge inspection during the project.

“There’s a lot of work items to be done—the finer details,” according to Andrea Clifford, Public Information Officer for the Kentucky Department of Highways District 5 Office in Louisville. “They see all of the pieces of the truss there but getting everything bolted down in place and getting ready for the concrete deck, there’s a lot of steps to be taken.”

Stover said “a pretty good analogy” of comparison between the construction of the new bridge and a residential structure is once the shell of a house is complete people get excited because they think the house is almost finished. Often, more work remains to be done on the inside of the shell than it took to erect the shell in the first place.

Construction of span 1, the site-built section of truss on the Milton side, has progressed to the point where the truss has reached temporary pier 2. This section of truss was built in place projecting toward the Milton shore from Span 2, which was lifted into place using a method called strand-jacking in late June.

Work is also progressing on span 4, the site-built section of truss on the Madison side of the river. This span extends from Span 3, which was jack-lifted into place over the navigational channel of the Ohio River in September, toward the Indiana shoreline.

“Once that truss is complete from shoreline to shoreline then they’ll need to go in and place the concrete deck so the vehicles can drive across that bridge,” Stover said.

Stover said the bridge decking should be in place sometime after the first of the year and traffic will be switched over to the new truss on the temporary piers at that time.

Walsh Construction, Co., the contractor erecting the new bridge, completed paving work on the reworked Milton approach to the bridge last week. Concrete girders have been set in place for the permanent ramp on the Milton side and for a section of ramp that will connect to the new truss in its temporary location. Walsh personnel are currently at work placing the stay-in-place decking materials preparatory to pouring the concrete decking on the ramps.

“You’ve seen those stay in place forms that go in between the concrete beams,” Stover said. “A similar system will be used on the truss between the steel stringers that are out there now. They’ll get that same stay in place decking with rebar across the deck and an eight-inch-thick concrete deck on top.”

That process is well underway on the Madison approach ramp to the bridge where part of the ramp decking has already been poured.

Workers have also been installing steel framework for the temporary transition spans on each end of the bridge that will be used to transfer traffic from the completed permanent approach ramps to the new truss in its temporary location downstream from the existing bridge structure.

The transition spans will be similar construction to the temporary ramps (with timbers and asphalt) that have been used by traffic to access the bridge since the original approach spans were demolished last summer. Sometime after the first of the year traffic will be rerouted from the current temporary ramps to the new transition spans and onto the new truss while the truss is still mounted on the temporary piers. At that time crews will begin dismantling the temporary ramps that are currently in use.

“The project’s got as much momentum as ever in terms of construction of the approaches on both the Kentucky side and the Indiana side leading up to the bridge,” Stover said.

Preparing for the truss slide

Once traffic is rerouted onto the new truss on temporary piers a demolition contractor will begin dismantling the original truss and bridge floor, Stover said. Once the truss is removed, then the renovated piers 3, 4 and 5 will be tapered out to accept the wider new truss.

The process of sliding the new truss from the temporary piers onto the renovated permanent piers will occur sometime in the spring, “in the April or May time frame,” Stover said.
“There’s actually going to be two slides that will happen,” he said. “The first one will be the full-length span—the 2,427 feet will go simultaneously. Then there will be a second slide consisting of the shorter span of concrete girders.”

The reason for that involves the land-borne pier on the Milton riverbank. That pier, which is currently supporting the temporary ramp and the end of the original truss, has to be widened out to accept the larger width of the new truss so that work has to occur once everything is removed from atop it. By contrast, a new land-borne pier has been constructed on the Indiana side on which the new truss will land. There won’t be a need for a separate slide of a shorter span over there, Stover said.

The original pier closest to the riverbank on the Indiana side will probably be dismantled prior to the slide just to make it easier to work, he added. That pier will not be necessary to support the new truss.

No realignment of Milton approach

Both Stover and Clifford said no current plans are in place to change the approach to the bridge on the Kentucky side. The subject has arisen many times in several studies dating to the 1980s because of the constant maintenance that the Milton Hill road requires, the inconvenience of the intersections in downtown Milton, and thirdly the fact that the current access to the bridge is in the flood plain.

“Currently there’s not a project in the highway plan to address that,” Clifford said. “It’s been thought of before and I’m sure the legislators in this area would need to work to secure funding for that.”

“It was looked at preliminarily in the environmental phase” of planning for the current replacement project, Stover said. “There were options to go on up to the Milton Hill from the end of the bridge as it is now or to continue up School Hollow Road.”

“I think right now the major focus is to get the bridge completed,” Clifford said. “That’s been the urgent need. I know the hill is an issue there. But you also have to look at what would the approach look like and where would you reconnect that?”

Stover and Clifford agreed that rerouting the approach to the bridge would involve years of study and securing rights of way. Stover said the new bridge was designed to be the same width from end to end to the receiving abutments with no tapering so that future engineers could tie-in with whatever ultimate approach might be decided on. It is easily tied into going forward.

The pedestrian walkway will not be completed until after the truss is slid into position, Stover and Clifford said. There will be some work to be done on that pedestrian path after the slide. When the bridge is slid into place pedestrians won’t be able to walk across it on day one.

Scour protection

Meanwhile, scour protection continues with installation of boulders and fabric at piers 3, 4 and 5. Scour is caused by swiftly moving water past the piers and can cause erosion. Stover said engineers could find no record of the installation of any protection against scour around the original piers when the bridge was built in 1929.

“The scour protection work will have to be completed” after the new bridge is in place on the renovated piers, Stover said. “They’re able to do the work to the upstream side of the piers. They’ll have to complete the downstream side after the temporary towers have been removed.”

Site cleanup work will continue for four to six months after the new bridge is open to traffic in its permanent location. They’ve got to remove the temporary towers and pull any piling that’s in the river.