(Francisco Kjolseth | The Salt Lake Tribune) Crew members Meli Kaufausi, left, and Simone Katoa work on the extensive structural integrity of a bridge beam at Forterra Structural Precast in Kearns on Tuesday, Dec. 11, 2018. UDOT is in the process of placing some of the world's largest-ever bridge beams, with the same design, along the technology corridor in Lehi later this week.
Most newer concrete beams that hold up Utah highway bridges are around 145 feet long. But the Utah Department of Transportation is about to place six that are 40 percent longer — 203 feet — to help widen Interstate 15 in Lehi.
They are longer than the iconic Cinderella’s castle in Walt Disney World (189 feet) is high, or the leaning tower of Pisa (185 feet).
They also will be the third-longest single-component beams in the United States, slightly shorter than two in Orlando, Fla., and Seattle, said Lee Wegner, with Forterra Structural Precast, the West Valley City company that is making them.
They may also create a bit of a spectacle along Utah highways over the next few days. They are being shipped one at a time on long, wide trailers that take up two lanes of traffic — with Highway Patrol and pilot car escorts — and will mostly travel on freeways.
And crews will have “two massive cranes out there dropping pretty massive beams into place” in Lehi over a four-day process beginning probably on Thursday, said UDOT spokesman John Gleason.
The beams are being installed where I-15 crosses over some rail tracks and trails between the Lehi Main Street and 2100 North exits, and will help widen the freeway as part of the Technology Corridor project. Installation is not expected to interfere with or slow I-15 traffic, which is detoured around the work location.
“They are massive,” Wegner said about the beams. “They are roughly 225,000 pounds — a quarter-million pounds. They are just over 8 feet deep.”
He adds, “Up until probably the last five to 10 years, the technology did not exist to stretch them out to what we can do now.”
The pre-stressed concrete beams contain “68 half-inch-diameter steel cables running down the middle of them. Each one of those cables is pulled to about 44,000 pounds of stress,” Wegner said.
“With 68 in there, there is roughly 3 million pounds of force within the beam,” he said. “One of my engineers who used to work for Thiokol tells me that is enough to get the space shuttle into orbit.”
Once the steel cables are stretched and stressed, he said, “The concrete is poured around them and is allowed to cure. Once it is cured to a specified strength, the cables are cut, and that force is then introduced into the concrete. So they have 3 million pounds of stored force just sitting there.”
Wegner said, “That allows you to turn a piece of concrete that is inherently weak in tension into something that is able to counteract tension” and support heavy traffic loads.
He added, “We use a super-high-strength concrete,” which can cure to needed strength overnight.
UDOT is using the upcoming transport and placement of the beams to urge drivers to slow down through I-15 construction in Utah County. The speed limit has been lowered to 60 mph there, but Gleason said far too many drivers are going faster.
“We still seeing a lot of people who are traveling too fast,” Gleason said. “The speed limit is there to protect all of us. The lanes are narrowed. They are winding. Sixty mph is a safe speed.”
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