Green Street Pedestrian Bridge

The new Green Street Pedestrian and Bicycle Bridge is a unique multi-ribbed, unbraced, tied-arch structure spanning the newly reconstructed Salem Parkway.

Located in the downtown area of Winston-Salem, N.C., it reconnects the West Salem neighborhood with the city’s multi-use path, a nearby baseball stadium, and new developments planned for the area. The arching structure serves as an artful, iconic gateway into downtown that inspires economic development and symbolizes Winston-Salem’s 21st-century aspirations.

The North Carolina Department of Transportation (NCDOT), along with Winston-Salem’s Creative Corridors Coalition, provided a bridge concept and aesthetic requirements. Without a design precedent to rely upon, the team took the aesthetic vision and transformed it into a viable design. The team collaborated with stakeholders and the City’s Creative Corridors Design Review Committee to understand and meet expectations on the bridge’s unique features, including geometries, arch shape, hanger rod arrangement, and connection details.

The 32-ft-tall pair of inner arches incline 13° outward from a vertical plane and primarily carry the bridge’s dead load. The lower pair of outer arches reach a height of 16 ft and incline 30° outward, supporting pedestrian live loading while carrying a smaller portion of the dead load. Each rib contributing to the overall bridge structure’s primary load path required a strategic design approach and a multi-phased staged structural analysis.

Cambered 6 in. at mid-span, the gently-curving bridge deck is supported by a series of radially aligned, stainless-steel hanger rods—nine hanger rods to each arch rib for a total of 36 hangers. For each arch, the plane of the hanger rod group is offset from the centerline plane of the arch rib to provide a constant deck cross section and avoid outriggers. This approach improves the structural stability of the unbraced arch ribs by providing a restoring force against the outward torsional tendency of the ribs’ selfweight. Shop-welded upper gusset plates are aligned longitudinally along each steel arch rib and connect the high-strength stainless steel hanger rods to the arches using forks and spherical bearing assemblies. Embedded at the deck level, gusset/base plate anchorages accommodate the dual arch rib configuration. These hanger anchorages uniformly align along each of the bridge’s concrete edge beams and provide connection points for the stainless-steel hanger rods between the arch ribs and the bridge deck through forks and spherical bearing assemblies.

The bridge also employs concrete pilasters aligned to accommodate the varying arch rib base plates, which anchor to the pilasters through tension rods. The pilasters were critical aspects since all the arch ribs terminated at this location to tie the deck and foundations together. The unique pilaster geometry was driven by the arch rib geometry and the need to simplify steel fabrication at the base plate ends. The pilaster became a geometric nexus that accommodated a wide range of complex geometries, force transfer, and anchor rod alignments in a central location. Combining augmented reality, real-time 3D model viewing, and even a 3D printed model, the team achieved stronger design communication.

HDR’s structural engineer developed a powerful centralized parametric bridge design model that was leveraged to balance geometric complexity and design risk and improve confidence in the structural concept. The parametric model allowed for early insights into the structure that would not have been possible any other way due to the geometric complexity and direct influence on design elements. By automating structural models, the team could explore, evaluate, and optimize structural design aspects in ways never previously achieved. The model was beneficial in the staged analysis of the structure and proved to be an efficient way to understand the behavior of the different unique bridge elements and effectively generate production data.

Leveraging state-of-the-art structural engineering tools, signature bridge expertise, and strong technical collaboration between multiple stakeholders, the Green Street Pedestrian Bridge’s design tackled aesthetically driven complexities and constructability implications head-on. The team delivered the client’s vision through a design that employed structural innovation and ingenuity by leveraging a centralized parametric design approach, expertise, collaboration, and a drive towards practicality for construction.

Project Team

• Steel Team

  • Fabricator: King Fabrication LLC, Houston *AISC CERTIFIED*

  • Bender-Roller: Bendco, Pasadena, Texas *AISC CERTIFIED*

• Owner: City of Winston-Salem

• General Contractor: Flatiron Corp.

• Structural Engineer: HDR