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Colorado Bridge

Situation:

U.S. 191 crosses the Colorado River near Moab, Utah, connecting an estimated 1.5 million people a year to the area’s stunning rock formations, trails and national parks. It also serves as part of a major freight corridor that runs from the Four Corners area to Salt Lake City and Denver. The Utah Department of Transportation (UDOT) estimates that a third or more of the traffic comprises semi-trucks and trailers.

Challenge:

Among the goals of the bridge replacement project was to create an aesthetically pleasing structure that would blend into the surrounding landscape. To help achieve this, a segmental bridge design was selected. A major benefit of segmental design is that the precast elements achieve a higher quality of finish and greater strength than cast-in-place box girders.

Segmental bridges also can span greater distances through the combination of post-tensioning and higher compressive strength of the segmental units. This allows for a thinner, more graceful profile with fewer columns.

The layout of the twin bridges, each with spans of 292 feet, 438 feet and 292 feet and only one pier in the water, was also planned to further reduce impacts to the river.

The challenge facing the construction crew was to build these segmental bridges efficiently, economically and with no disruption to existing traffic.

Solution:

The solution involved the use of a unique form traveler system and a little help from SPX.

Engineered to international standards, the form traveler system provides exceptional rigid formwork with a maximum deflection of less than 25 mm at full loading. The system is used to set up forms into which concrete is poured to construct bridge segments one at a time on each side of two large piers. When a counterbalancing segment is finished on each side of the pier, hydraulic equipment moves the form so another segment can be added until the spans meet in the middle between the two piers.

SPX supplied its Power Team® brand high-pressure and low-pressure hydraulic systems to create a complete solution for this movable formwork system.

Process:

Construction crews first built a temporary 400-feet-long bridge from which to work, so as not to disrupt traffic on the existing bridge. They also had to build two large piers to support the concrete bridge.

Using Power Team hydraulic equipment supplied with the form traveler system, the construction crew launched the form traveler on rails to the first segment location. There they aligned and leveled the external formwork and then fixed it into place. Reinforcing steel was placed in the bottom slab and web walls. The interior formwork assembly was then advanced, and the top deck slab soffit and wall forms leveled and fixed into place.

Reinforcing steel and post-tensioning tendons were placed in the deck slab, bottom slab, web wall and deck slab concrete. The post-tensioning tendons were stressed and the internal and external formwork stripped from the cast, cured segment. Power Team equipment was then used again to launch the form traveler to the next segment.

Upon completion of the first bridge structure, traffic was rerouted from the existing bridge to the new two-lane structure. Full four-lane traffic opened with the completion of the second bridge structure.

Result:

The project was completed the end of 2010.