As steel girders arrived on site for the Juneau Creek Bridge launch, they were set with straddle cranes and then bolted together with cross bracing and internal bracing.
Photo courtesy Traylor Bros.

It took seven June days to launch the steel across the canyon. “It was very nerve-racking,” says Bridget Monahan, Juneau Creek Bridge project manager for bridge contractor Traylor Bros. “It was all hands on deck. It was about communication.”

The bridge design, led by the Alaska DOT in conjunction with Traylor as part of the CMGM project, started with over a dozen different bridge options, from cable stay to segmental concrete to several different kinds of arches. With the contractor on board, the team investigated each possibility in terms of pricing and constructibility.

Three main factors pushed the team toward the steel girder design. The project featured the longest-running environmental impact statement in the nation, stretching nearly 40 years, says Jonathan Tymick, project manager for the Alaska DOT. The requirements left no leeway to put construction in the canyon, not even temporary shoring.

A geotechnical analysis of the shallow groundwater site showed that raising the elevation of the bridge was best. Once the roadway profile elevated to a certain point, that alone helped eliminate concepts. Mix in the seasonality of the area and wind load issues with leaving structures—or cranes—up through the winter, the DOT was left with launching a steel girder bridge.

The girder pieces, weighing up to 150,000 lb each, were fabricated in Arizona, shipped through Long Beach, Calif., to Seward, Alaska, and then trucked to the site in assembly order.
Photo courtesy Traylor Bros.

“Frankly, it wasn’t the cheapest bridge to build,” says Nicholas Murray, design squad lead for bridge design at the Alaska DOT. “It looks spectacularly cool but was driven by the need to use that construction method. Any normal bridge we can get regular crane access to. This is such an involved and expensive way to do this.”

The $151-million contract to Traylor Bros. is part of a larger $850-million highway project. “It’s unreal the size and complexity of the project,” says Mohamad Ramlawi, area manager for Traylor Bros. He says the canyon and the wind loads—needing to design for 146 mph for three second gusts if constructing over winter—and the lack of a year-round work schedule pushed the team into the steel-plate girder structure.

The launch eliminated the seasonality concerns of having structures sitting through winter and allowed a reduction in wind speed loads. Launching the bridge also removed cranes that would have been tricky—if not impossible—to get on site.

Still, the seven-day bridge launch was years in the planning. The team erected the bridge on the ground and opted for “launching in one fell swoop,” Murray says. Winds are at their lowest in June, helping assuage fears of galloping or vortex shedding, “things you think you’ll never have to worry about on a normal bridge,” he adds.

The construction team assembled the bridge on the ground and launched it in one effort when wind speeds were at their lowest.
Photo courtesy Traylor Bros.

The five girder sections necessitated 45 steel girder pieces, each 13 ft, 3 in. deep and ranging from 90 to 120 ft in length. The pieces each weighed up to 150,000 lb, requiring the team to fabricate 400-ton hydraulic rollers to push them across the canyon. The most intense load demands ever to be placed on the bridge girders came during the launch.

As steel girders arrived on site, they were set with straddle cranes and then bolted together for the launch. Alignment issues were the main concern as the launch progressed. Marcus Forkner, project engineer for the Alaska DOT, says during the launch the issues were keeping the rollers exactly where they needed to be, with only 1 in. of tolerance allowed. To make sure the segments were in alignment, the girder couldn’t move north to south at all.

The hydraulic rams sent the bridge across, with four rams each needing to push about 50,000 lb. The bridge now features 6 million lb of permanent steel. “It is a relatively simple bridge, but really big,” Murray says.

A series of 400-ton hydraulic rollers were fabricated to push the massive 6-million-lb steel structure across the canyon.
Photo courtesy Traylor Bros.

Ramlawi says they used a sensitive monitoring system to watch the rollers and jacks working in conjunction. Traylor had a fabrication shop on site, ensuring that they could make shim plates as needed. The monitoring system allowed the crew to watch loads and be alerted if the rollers came out of plumb.

“Everyone kept their cool; we’d stop the launch and address as needed,” Monahan says. “We were trying to get ahead of it and fabricate parts and pieces so we could proceed forward immediately.”

The logistical process started well before steel reached the canyon rim. All the steel was fabricated in Coolidge, Ariz., trucked to the Port of Long Beach in California, barged to Seward, Alaska, and then trucked to the site.

“The transportation of all this fabricated steel from Arizona to Alaska wasn’t an easy thing,” Ramlawi says. The barges had to support the weight of the steel in open water. Then crews off-loaded girders and trucked them to the jobsite in the order of assembly. All this had to be vetted, requiring six months of planning. With the pieces 13 ft tall, the trucks took a special route to avoid low overpasses during certain time windows due to road restrictions. Monahan says that spreading loads out was crucial in the planning, and she was always asking, “How much does that weigh and how many trucks do you need?”

Environmental restrictions barred construction in the canyon, and the location of the bridge demanded that it be designed to withstand wind gusts of 146 mph.
Photo courtesy Traylor Bros.

The remote location was difficult at every step of the process, with crews requiring two sets of everything for redundancy due to the time it took to haul in the parts. The specialized equipment required pieces that were sourced from across the world, with the cable stays, for example, coming from Switzerland.

This is a new section of road, so there wasn’t a paved highway to the site. The team had to get the road ready to haul the giant girder segments, and once they came off the truck at the site, they were staged for the launch. It was a live assembly—as the truck drove onto the site, two straddle cranes picked the girder and moved it into place, securing the cross bracing and internal bracing before immediately sending it to its permanent position. Traylor assembled the superstructure behind the abutment and hydraulically launched it across the canyon.

Monahan admits it was a taxing week of work, and she couldn’t relax until the final moment. “When they said we are down to three inches, two inches, one inch, checking, and then [said] ‘Lock it down,’ then I could breathe,” she says.

Murray says the team is over the last big hurdle. Following the launch, crews jacked the bridge up to remove the rollers and then, in increments of 10 in., jacked the bridge down a total of 40 in. to rest on bearing pads. The team will then remove the king post and support structures. In 2027, crews expect to complete the concrete decking. As an early phase of a larger project, the highway won’t open to traffic until the end of 2030.

“You’ll look up,” Monahan says of the simplicity of the design, “and just see a steel line go across the tree line.”