ADVERTISEMENT

New Larpenteur Avenue bridge will be pushed into place Wed. night

  • Article by: Tim Harlow
  • Star Tribune
  • July 8, 2014 - 9:12 PM

With hydraulic jacks providing the oomph and “concrete shoes” with Teflon pads underneath to give it glide, the new Larpenteur Avenue bridge will be pushed into place over Interstate 35E during the overnight hours Wednesday into Thursday.

The Minnesota Department of Transportation will close both directions of I-35E between I-94 and Hwy. 36 from 9 p.m. Wednesday to 5 a.m. Thursday when it uses a technique called slide-in bridge construction, something that has been used in a few other states and is being tried in Minnesota for the first time.

“It’s pretty cool,” said MnDOT spokeswoman Bobbie Dahlke.

It will take up to eight hours to move the 3.5-million-pound deck and beams from a nearby temporary structure where they were built onto the newly constructed piers and abutments.

MnDOT will use hydraulic jacks that will methodically move the bridge laterally at a rate of 19 inches per stroke to cover the distance of 84 feet.

Motorists on Wednesday will find lane restrictions in the vicinity of Larpenteur Avenue beginning at 7 p.m., and several ramps will shut down at 8 p.m. Motorists will be detoured around the closure on I-694 and I-94.

Building the deck for the new bridge on temporary framework to the north allowed MnDOT to keep Larpenteur open to traffic longer and minimize the length of traffic disruptions, MnDOT said. The estimated time frame from the closure of the old bridge to opening of the new one is estimated at 35 days, compared with 60 days for bridges of similar size recently built at Arlington Avenue and Wheelock Parkway, MnDOT said.

The technique is among the latest innovations the Federal Highway Administration is urging states to use to shorten projects, enhance safety and mitigate environmental impact.

The method has been tried in Oregon, Utah, Missouri, Michigan, Colorado and Massachusetts, and other states are now looking at using it.

Different from recent bridges

Slide-in bridge construction, which allows bridges to be moved laterally only, is different from the method used on the recently completed bridges at Arlington Avenue and Wheelock Parkway. Those bridges were built off-site and moved into place with a vehicle that jacks up the beams and deck from its staging area and moves the superstructure laterally, vertically and even in a circle if necessary.

MnDOT also used that technique when building the new Hastings Hwy. 61 bridge. That bridge was built on land, then loaded onto a barge and floated down the Mississippi River and lifted into place.

The new Larpenteur bridge consists of two spans, each 92 feet. MnDOT says it hopes to capture the big move on video and share it on social media sites.

The bridge is part of the ongoing work along I-35E that will continue through 2015. The project includes adding a MnPass lane between Little Canada Road and Maryland Avenue, rebuilding bridges along that stretch and resurfacing the freeway. Work also continues on rebuilding I-35E between Maryland and University avenues.

Tim Harlow • 612-673-7768

© 2014 Star Tribune