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Workers are building a replacement bridge, right, next to the current bridge on I-75 over U.S. 6 to be slid into place. The method reduces motorists’ headaches during traffic disruptions.
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On I-75, new bridges slated to move in

THE BLADE/ANDY MORRISON

On I-75, new bridges slated to move in

Bowling Green ‘slide’ spans will be Ohio’s 1st

BOWLING GREEN — Replacing a freeway bridge typically takes months, if not years, of lane closings, traffic shifts, or both.

But when an Ohio Department of Transportation contractor tears down the I-75 bridges over U.S. 6 and installs new ones later this year, freeway traffic will be disrupted for just two weekends, roughly 60 hours from Friday evening until Monday morning.

The key is the word “install” because the new bridges will already have been built. What will happen during those 60-hour windows is they’ll be moved into position from temporary support structures next to I-75 upon which they’re now being assembled.

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“Over one weekend, we’ll tear the old bridge down and slide it [the new one] into place,” said Todd Lezon, the area manager for Kokosing Construction Co. “On a second weekend, we’ll do the other one.”

“Slide-in” bridge construction, also referred to as “lateral slide,” is a method increasingly used for replacing bridges with minimal traffic disruption.

Eight states, including Pennsylvania and Indiana, have established the method among their officially endorsed construction practices. Five more, including Michigan, have completed “slide-in” projects.

The I-75 bridges over U.S. 6 will be Ohio’s first to be built that way.

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Using traditional construction methods, contractors rebuild a bridge by closing one half of it at a time, often requiring lane closings that last for two construction seasons.

For bridges that will be widened, another option is to build the new lanes, then run traffic on those while rebuilding the old ones.

That is what ODOT is doing with several smaller bridges along I-75 between Perrysburg and Findlay, where the freeway is being widened from four lanes to six.

But department officials began planning the bridge replacements at U.S. 6 as something that needed to be done regardless of whether the rest of I-75 was rebuilt.

“It was designed as a stand-alone project, then it got incorporated into the widening project when funding became available,” said Brian French, an ODOT area engineer who estimated the bridge itself represents about a $7 million expense.

While the “slide-in” method will cost a little more than conventional bridge-building would have, “it gives ODOT the experience, and it gives the contractors the experience, of doing a project like this,” Mr. French said.

Added Mr. Lezon: “This takes an absolute ton of preplanning. The sheer amount of expense to make all that fit is pretty dramatic.”

But Jamal Elkaissi, a structural engineer at the Federal Highway Administration Resource Center in Lakewood, Colo., said that the higher direct cost of “slide-in” construction is typically more than offset by its time and safety advantages.

“The longer reconstruction extends, the longer that a possibly hazardous condition exists,” Mr. Elkaissi said.

Work-zone congestion also costs motorists time and money, wastes fuel, and harms nearby businesses. In the past, the highway administration engineer said, “there was no mechanism established” to calculate those indirect costs, but now statistical models are available.

Once all the indirect costs are factored in, “you come in cheaper to use this technology,” Mr. Elkaissi said, adding that as “slide-in” construction becomes more widely used, its cost will fall as contractors become more experienced and comfortable with the method.

Michigan used the slide-in method for the first time last year when it replaced three bridges: the M-50 bridge over I-96 near Grand Rapids and twin U.S. 131 bridges over Three Mile Road in Mecosta County.

Matt Chynoweth, who until three months ago was the Michigan Department of Transportation’s state bridge engineer, said the U.S. 131 structures used that method because it reduced the disruption to heavy traffic associated with nearby Ferris State University, while replacing the M-50 bridge that way avoided a circuitous, long-term detour.

In the M-50 case, Mr. Chynoweth said, the new bridge was built on a temporary structure, then it was connected to a temporary roadway alignment while the old concrete structure was torn down.

Once a new pier and abutments were built on the permanent route, the new bridge was closed again to traffic so it could be moved into its permanent position, the MDOT engineer said. The brief M-50 closings required brief I-96 “up-and-over” detours through the M-50 interchange ramps.

Mr. Chynoweth said “slide-in” construction added about $1 million to the MDOT U.S. 131 project’s direct cost and about $750,000 to the price for the M-50 bridge, but the benefit to motorists was worth it.

“We’re treating it as a tool in the toolbox — something we can use when there’s a long detour or the user-delay costs are not palatable,” Mr. Chynoweth said.

This year MDOT is replacing a bridge on M-100 over Canadian National Railway tracks in Potterville using the lateral-slide concept, but with rollers on a track instead of slide pads and a rail for the transfer.

Mr. Lezon noted sliding can be done in several ways, but he declined to say which one Kokosing will use for the I-75 bridges because that’s “proprietary information.”

The on-going construction has required restricting U.S. 6 to one lane each way instead of its normal two, but that highway’s traffic is light enough that the lane closings haven’t caused problems with congestion.

Besides the new bridges’ construction, preparatory work includes building the abutments underneath the existing bridges’ approach spans.

The existing bridges have four spans — one over each direction of U.S. 6 traffic plus one at each end above an earthen slope leading up to their abutments. The replacements will have just two, with abutments built of “mechanically stabilized earth” — increasingly familiar structures with walls resembling interlocked jigsaw-puzzle pieces — at either end.

Plans call for the northbound I-75 bridge to be replaced first, tentatively on a late-summer weekend.

From 6 p.m. Friday until 6 a.m. Monday, northbound traffic will be divided through the work area, with one northbound lane crossed over to the southbound side while the other will be detoured through the U.S. 6 interchange ramps.

The southbound bridge will be replaced at least several weeks later using similar traffic patterns. U.S. 6 will be closed both weekends.

Contact David Patch at: dpatch@theblade.com or 419-724-6094.

First Published June 22, 2015, 4:00 a.m.

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Workers are building a replacement bridge, right, next to the current bridge on I-75 over U.S. 6 to be slid into place. The method reduces motorists’ headaches during traffic disruptions.  (THE BLADE/ANDY MORRISON)  Buy Image
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