The Utah Dept. of Transportation moved an Interstate 215 bridge into place during the weekend of Aug. 23 using self-propelled modular transporters in Salt Lake City. It was the 12th structure placed with SPMTs this summer, capping a whirlwind of accelerated bridge construction activity in a state program called Innovate 80.

Brad Fullmer

Brad Fullmer Utah has replaced a dozen bridges using self-propelled modular transporters this summer.

The 33rd South bridge at I-215 was the last of eight bridges constructed this year by Draper, Utah-based Ralph L. Wadsworth Construction Co. and moved into place with SPMTs operated by Mammoet USA, Rosharon, Texas. The other seven were placed during a six-week period along the I-80 reconstruction corridor from June to early August.

The $4.5-million bridge was placed in just 19 hours—36 hours less than the 55-hour window allotted. Wadsworth supervisor Doug Clements says moving the bridge from its staging area about 1.5 miles south of the project site was difficult because of utilities. Steel plates were set over a high-pressure gas line along a major road as a cautionary measure. Traffic signals, power lines and other utilities were removed and replaced to allow for the move.

The 80-ft-wide, 130-ft-long, 1.6-million-lb bridge uses a lightweight aggregate made by Coalville, Utah-based Utelite. The aggregate weighs about 115 lb per sq ft, compared to 150 lb per sq ft for regular stone, says Jim Deschenes, assistant vice president with Michael Baker Corp., whose Midvale, Utah, office is design engineer. “Most of the weight savings was in the lightweight concrete, along with optimized steel girders,” says Deschenes.

Clements says the Accelerated Bridge Construction (ABC) process with SPMTs has gotten smoother with experience, but adds that nothing can ever be taken for granted when dealing with mammoth bridge structures.

Wadsworth Bros. Construction (WBC), Draper, replaced four bridges on I-80 in Parley’s Canyon, east of Salt Lake City, over two weekends in mid-August, taking just 37 hours. “It’s the fastest bridge replacement I’ve ever heard of,” says Deryl Mayhew, UDOT resident engineer on the $11-million project.

WBC proposed using SPMTs after it won the design-build job. “We were given the choice to do it by having bypass roads and diverting traffic on I-80 around the bridges and doing it at our own pace,” says Guy Wadsworth, WBC president. “We figured the geometry wouldn’t work, so at the last minute we decided to use SPMTs. We had to put together [another] bid in five days.”

The new approach slabs for the four structures were built adjacent to the existing bridges. Casting included post-tensioning ducts that were embedded in the monolithic slabs with reinforcing steel. After the slabs cured, they were cut into segments, lifted into their final positions and post-tensioned together.

Wadsworth says the four approach slabs each weighed about 54,000 lb. “It’s difficult to replace approach slabs,” he adds. “The grade had to be nearly perfect to set them.”

Mayhew estimates that typical construction methods would have caused traffic delays up to an hour in each direction, with a six-month schedule. Using SPMTs saved 190,000 hours of delays, which he says equates to over $2.5 million.

Bill Halsband, vice president of business development for Mammoet, says UDOT has led the way in utilizing SMPTs. Oregon, Florida, Washington, Louisiana and New York have done at least one accelerated bridge project.