A man moved a 3 million-pound bridge from 1300 East to Highland Drive along I-80 Saturday night using a joy stick wired to a self-propelled modular transport system. Yet for the bridge to reach its final destination this week, it will take dish soap, wooden blocks imported from Africa and clever minds, along with lots of patience from motorists.
Moving the first bridge to be installed along I-80 begins a process of leap-frog construction that will take place between 1300 East and State Street. For months, crews have been casting the decks for seven bridges that will replace existing structures at Highland Drive, 900 East, 700 East, 600 East, 500 East and 300 East. The movement and placement of the bridges will run through the first week of August, Utah Department of Transportation officials estimate.
Crews were expecting to have the first bridge in place over the weekend, but because of concerns about a bend in the carrying beam, the project was delayed. On Sunday afternoon, crews were welding additional supports to the beam. Today, UDOT is hoping to place the bridge across the gap and begin lowering it into place.
"We're playing it safe and handling things with care," said John Montoya, project manager for the site. "It's not worth the chance. There isn't a second one."
That means commuters will face delays this morning. During bridge movements and placements, westbound I-80 will be reduced to a single lane and eastbound traffic to two. As crews are preparing for other moves, both eastbound and westbound lanes will have two lanes open.
Montoya is expecting the bridge to be resting in its final location Tuesday. Soon after the bridge is placed, crews will begin buttressing the underside of the structure so it can support other bridges as they move over Highland Drive.
To move the structures from the bridge "farm" located along the 1300 East westbound onramp, crews are using accelerated bridge construction methods that are a first for the industry. Previous bridge replacements in the state have used similar steps in the process, but the scale of the project and new approach to placing bridges is gaining attention around the nation.
UDOT officials say that the benefits from these new technologies have reduced the overall congestion of traffic through the construction process and saved both time and money for the department.
To move structures that weigh between 2 million and 3 million pounds to their designated place along I-80, crews use a self-propelled modular transport system, Montoya said. It crawls under the bridge and uses a hydraulic lift system to raise the bridge about 10 feet off the ground so it can be moved to its destination.
The system consists of four transports that are connected through a computer system. Each transport houses 72 wheels that can collectively bear the weight of the bridges. The transport system can move in any direction and even make minor adjustments between its transports to accommodate uneven surfaces.
As the bridge reaches the gap it will eventually fill, four skid shoes are welded to support beams below the bridge. Like a roller skate, the skid shoes will slide the bridge across tracked beams lubricated with dish soap that span the gap. The bridge will be slowly pushed and pulled across the gap by a hydraulic ram until it is in position above hydraulic jacks resting on the street below. The jacks are encased by numerous blocks of ironwood, an extremely dense wood that sinks in water.Once the bridge is resting on the hydraulic jacks, it becomes a sort of controlled Jenga game to lower the structure the remaining 15 feet, Montoya said. The jacks lift the bridge off the ironwood supports, it is locked in place with steel pins, a layer of wooden blocks is removed, and the jack is lowered again. Each time a layer of ironwood blocks is removed, the bridge is lowered four inches.
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