Kentucky’s Tallest Bridge Built by “Incremental Launching” (Time-Lapse Video)

Builders of Kentucky’s new tallest bridge used an incremental launching method, not commonly performed in the U.S., to construct the span in rugged terrain 324 feet high.

The incremental launching method has been more widely adopted in Europe and is most often used when a bridge cannot be erected from below the superstructure, such as when it is over deep valleys, deep water crossings or steep slopes. It was the first time the process had been used in Kentucky. (To watch a time-lapse video of the bridge launch, see the end of this story.)

The twin-span Pond Creek Bridge on U.S. 460 in Pike County, Kentucky, was designed to be 1,000 feet long and built between steep slopes over a creek, railroad tracks and a county road. “This made conventional erection almost impossible,” said Paul Burchett, co-founder of Bush & Burchett, the contractor on the $27 million project.

So the company built the two-span steel bridge at an area on the embankment and then incrementally pulled assembled girder sections onto the eight piers. The process involved two 70-ton hydraulic strand jacks and industrial Hilman rollers to pull the sections into position.

The work was done in segments. As girder sections were completed in the launch bay, the strand jack system was used to pull them onto the bridge piers, according to Engineered Rigging, which rented out the strand jack system as well as provided an on-site technician to operate it.

There are 10 bridge sections in all, five for each of the two bridge spans.

girders for second span of Pond Creek Bridge in Pike County Kentucky are launchedThe launching of the second span of steel girders for the Pond Creek Bridge in Kentucky.Kentucky Transportation CabinetOne of the challenges in the launch was having only a half-inch margin of tolerance with each gap for fitting the girders on the piers.

“Any lateral movement of the girders or minimal inconsistencies in fabrication of the girders or rollers led to rollers not lining up with the gap in the splice plates,” Burchett said. That caused some delays on launching the eastbound span. To reduce the problem on the westbound span, the splice plates on the bridge were modified.

After the launch was completed, the bridge was lifted off the Hilman rollers to allow the bridge to sit on its bearings. The process involved four locking pancake jacks, each with 160-ton lifting capacity, Engineered Rigging said.

“This was the first time a girder launch has ever been performed in Kentucky, and I was glad to be a part of it,” Burchett said. “We would definitely use the approach again if the conditions called for it. The designer, Stantec led by David Depp, Engineered Rigging, and the inspectors with KYTC (Kentucky Transportation Cabinet) did a great job of working with us to make this happen.”

Work on the project began in 2017. The last phase is expected to be let in 2023. The bridge is part of a larger $576 million project to build a new U.S. 460 in Pike County. When finished, it will provide a four-lane alternate for U.S. 460 from U.S. 23 near Yeager, Kentucky, to the Breaks Interstate Park near Breaks, Virginia.

To watch a time-lapse of the bridge launch between January 19, 2021, and June 30, 2022, courtesy of the Kentucky Transportation Cabinet, Bush & Burchett and TruLook, see below: