Bridge Construction Requires Flexible Formwork

Bridge Construction Requires Flexible Formwork

The integration capabilities of formwork products simplify the building process, especially when multiple products are required simultaneously.

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The Challenge:

In Burnet County, Texas, approximately 12,000 square feet of highway US-281, along with a steel-deck truss bridge crossing the Colorado River, is scheduled for removal and replacement.

The Players:

Doka and Archer Western Contractors

The Process:

The existing steel-deck truss bridge over the Colorado River in Marble Falls, Texas, was built some time ago and is no longer operationally efficient, necessitating its replacement.

The project involves demolishing the existing steel truss bridge and constructing twin cast-in-place segmental bridges. Each bridge will consist of three spans with variable depth segmental structures measuring 274, 410, and 274 feet in length, and a total bridge deck width of 47 feet. The use of the balanced cantilever construction method will allow the end spans to be built on falsework. Depth will vary from 23 feet at the center supports to 9 feet 6 inches at the end spans, with a super elevation of up to 5.5 percent.

A notable feature of the project is the bridge's V shape, which starts deep and tapers to a flatter form at the center span. This unique design necessitated flexible formwork solutions, as no two sections of the bridge would be the same.

Formwork Solution

The one-of-a-kind geometry of the proposed bridge required advanced collaboration between Doka and Archer Western Contractors. This necessitated the creation of forms that could adapt throughout the project. The differing span lengths and changing box depth demanded flexible formwork to satisfy various construction needs.

Archer Western selected Top 50 formwork panels, which could be customized to suit nearly any configuration, either in preassembly yards or directly at the job site. This choice reduced labor needs, maintained cost-effectiveness on-site and enhanced safety with integrated walkway brackets.

To construct the complex geometry of this bridge at a reasonable cost, Doka initially supported the pier table utilizing the Staxo high-performance shoring system and employed Top 50 formwork panels for the lower soffit, walls, and upper deck. The Staxo system offered high shoring capacity, versatility, and straightforward assembly with integrated couplers.

The pier table was completed in three pours. The design allowed for stacking formwork, minimizing the need for shoring and quick removal. Once the pier table was set, the traveler was positioned, and the segment formwork was assembled accordingly.

Similar to the pier table, the backspan will undergo a three-pour process in which Doka will again supply shoring and formwork, using both Staxo and Top 50.

Formwork Advantages

The ability of formwork products to cohesively integrate streamlined the process whenever multiple products were needed. This project featured innovative design elements, demanding creative and inventive solutions from the formwork supplier. Specifically, all forms from the pier table to the traveler had to accommodate geometric and field alterations, requiring a level of flexibility unachievable with conventional steel forms.

“What I appreciated the most about the Doka forms on this project is that they hinge when stripped,” commented Mike Wood, Project Superintendent for Archer Western. “With steel forms, we would have had to disassemble everything completely every time. However, with Doka, the forms remain intact, making it quick and easy to strip and reset.”

The outcome promises to be a beautifully designed, expertly constructed bridge that will benefit the community for years to come without the ongoing maintenance that the existing steel bridge demands.

Interested in learning more about Customizable Form Traveler for Bridges (es, in, vi)? Contact us today for expert consultation!