Double-Curved Pedestrian Bridge to Shorten Utah Valley University Commute

The bridge will connect the main campus of Utah Valley University (UVU) with the Orem Intermodal Transit Center, which is located across Interstate 15 and Union Pacific Railroad tracks.

“The new bridge will provide access for up to 6,000 students a day who take the UTA FrontRunner commuter train to UVU,” said Tom Cooper, project manager for WSP USA. “Commuters will be able to take a five-minute walk across the bridge instead of a 30-minute walk around, or a 20-minute shuttle ride.”

A June 14 groundbreaking ceremony marked the start of construction of the $15 million bridge. Design work began in September, and the bridge is targeted for completion in time for the start of the fall 2019 semester. The groundbreaking event included several speakers, including Richard Brunst, Orem City mayor; Matthew Holland, UVU president; and Greg Hughes, speaker of the Utah House of Representatives.

WSP is serving as the prime consultant, lead design engineer, structural designer, lighting designer, mechanical-electrical-plumbing designer, and the site civil designer for the project on behalf of UVU, the Utah Department of Transportation (UDOT) and the Utah Transit Authority (UTA). In addition to Cooper, the WSP team includes Josh Sletten, Utah structures manager; Rachel Cullen, design engineer; and Michael McDonagh, design engineer, with support from the Denver; Buffalo; Murray, Utah; and Lawrenceville, New Jersey structures teams.

The 1,000-foot-long pedestrian bridge will become the world’s first double-curved inverted Fink truss, according to Cooper.

“The Fink truss was originally a structure type used on railroad bridges in the late 19th century,” he said. “Over the past 20 years, the inverted Fink truss—simply, the Fink truss turned upside down—has been used as both a pedestrian and vehicular bridge as a simple alternative to a cable-stayed bridge.”

The double-curved bridge design emerged from UVU’s desire to provide an efficient connection between the transit station and the main campus, and to construct a highly-visible bridge in a style that complements the region’s rugged landscape. Those objectives resulted in features such as a high, open side enclosure; a vaulted roof; and a curved design that resembles a mountain ridge.

“For this project, the structure type met several of the key design objectives for uniqueness, and we could incorporate an impression of mountains without being too literal,” Cooper said. “The team was also able to develop a concept that met the client’s desires while staying true to the structural form.”

There are seven inverted Fink truss bridges in Europe and only one in the U.S. Only one of those bridges has a curved alignment and none of them are double-curved.

“The doubly curved inverted UVU Fink truss bridge will be the first of its kind,” Cooper said. “The UVU bridge is also the only one with a roof.”

Before the double-curved inverted Fink truss design was selected, it was evaluated against nine other structure options, comparing a long list of design objectives that included user comfort, compatibility with construction restrictions, cost and the feasibility of meeting UVU’s August 2019 construction deadline.

“It was compared against more traditional structure types, like prefabricated trusses, but because of the span length, width and requirement for a roof, this was actually the least expensive alternative,” Cooper said.

The efficient use of materials and limited superstructure depth of the inverted Fink truss also provides advantages over other bridge types, said Cooper, who added that the aesthetic appeal is preferable to other designs.

“As arranged, the roof appears to float above the deck instead of having a bridge with a roof or enclosure simply added to it,” he said.

Before settling on the atypical structure design, it was critical to get all three client agencies comfortable with the concept. The design team made every effort to address technical issues and looked ahead to all possible construction challenges before the design was selected.

“There has been and will continue to be a lot of collaboration on the project with our three clients and our subconsultant team, including the architect, Method Studio, and the construction contractor, Kraemer North America,” Cooper said.

Noteworthy in the design process was the implementation of building information modeling (BIM) and parametric modeling.

“We started the BIM process by building a Tekla model of just the bridge,” Cooper said. This model was uploaded into the Autodesk Revit® software platform as the design evolved, which allowed the architect, MEP team and lighting designers to work in an efficient environment. The team also uses SOFiSTiK, a FEM (finite element method) software platform that facilitates rapid model revisions to study structural alternatives within a compressed design schedule.

“Our approach to construct the bridge in a virtual setting, include design team members with fabrication and cable-stayed construction experience and work collaboratively with UDOT and the contractor form the basis for helping our clients get the bridge open within the one-year window we have for construction,” Cooper said.

Special provisions were made to ensure safety throughout construction:
• The selection of Kraemer North America was based on the contractor’s extensive experience on similar complex structures.
• Structural elements will not be erected over live traffic.
• A senior technical review group comprised of three senior WSP bridge designers was established to review the design, specifications, approach to construction staging, and other project elements that could present risk.

“While the structure is fundamentally simple, building a curved structure with such a complex geometry creates a construction challenge,” Cooper said. “Constructing something new—or as in this case a variation on something that’s been done before but is not common—means that our focus on constructing in a safe manner is heightened.”

The UVU pedestrian bridge posed engineering challenges that the WSP team welcomed.

“I enjoy projects where, as engineers, we are also able to be creative and where I can bring other people into that aspect of bridge design,” Cooper said. “This is one of those projects.”

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