Bridging Nature & Structure: Creating a Gateway to Bentonville’s Trail System

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Bentonville, Arkansas, has quickly become a mecca for culture, workforce talent, and outdoor recreation, with its population nearly doubling over the past decade. As a mountain-bike hub for Northwest Arkansas, the city is making its largest public space investment to date: the 8th Street Gateway Park. The park will serve as the centerpiece of the Bentonville Parks system and the western anchor of a 25-mile trail network, creating a destination for outdoor activity for both residents and regional audiences.

Serving as the structural engineer of record, Apex Engineers collaborated with PORT Urbanism, the Project Lead Architect and Lead Landscape Architect, as well as Polk Stanley Wilcox, the Architect of Record, to bring the park’s vision to life, creating structures that harmonize with, rather than compete against, the natural environment. The park is divided into three zones—West Park, East Park, and the Park Core—each offering unique landscape characteristics and recreational opportunities, requiring unique structural solutions. Its centerpiece, the Gateway Ring, forms a nearly two-thirds-mile pedestrian loop connecting key areas of the park while providing scenic overlooks that showcase the site’s rich natural character.

During the master planning process, the community played a central role in shaping the park’s vision. More than 300 people attended a Design Kickoff and Community Input Event, and the team collected over 300 pieces of feedback through comment cards, large-format maps with sticky notes, and preference dots placed on precedent imagery boards.

The structural scope within the East Park area of the project consisted of a comfort station, five boardwalks, and the Gateway Ring, which features two elevated pedestrian trails and two long-span truss bridges.

The comfort station is a 240-square-foot structure with CMU walls and a gabled roof made from cold-formed steel trusses. The walls and roof are clad with an architectural metal panel that is intended to visually match the weathering steel being used for the elevated pedestrian trail structures.

The boardwalks are constructed with pre-cast hollow core concrete planks and a 4-inch thick topping slab. They are at-grade and span across areas of the landscape which are depressed to allow water to flow across the site. Two of the boardwalks are single-span, two are three-span, and one is four-span. The multi-span boardwalks have cast-in-place concrete intermediate beams supported by round concrete pedestals and shallow foundations.

The structural scope within the West Park area of the project consisted of a 442-square-foot, partially underground comfort station. The all-concrete structure, including lid, walls, and foundations, was designed to support 24 inches of soil fill and pedestrian terrace live loading atop the structure.

Key architectural features include the sloping retaining walls forming the walkway to the entrance. The top of wall elevation varies from 15 feet 6 inches above top of footing to 4 feet 2 inches. The walls use two thicknesses—12 inches below grade to retain soil and 6 inches above grade for fall protection. The walls are clad with architectural metal panels that match the East Park Comfort Station, reinforcing a cohesive design language throughout the park.

The Park Core includes a central pavilion and retaining walls forming two bowl areas around a one-acre destination playground. The retaining walls range from 4 to 12 feet in height. One unique feature of these walls is the masonry veneer, which uses custom-shaped blocks to form bouldering walls.

The Park Core Pavilion is a 4,052 square-foot open-air structure constructed with hot-rolled steel frames and cold-formed metal stud wall framing. Early in design, the client expressed interest in preserving and converting the existing barn structures into a pavilion. However, the buildings were not in a condition that allowed for economically feasible reuse, leading the design team to develop a new design that honored the barns’ character while meeting modern structural requirements.

Lateral forces on the pavilion are resisted by a combination of steel cantilever columns in the exposed public assembly space and steel braced frames in the back-of-house spaces. The primary challenge for the bent frames was their length. The bent frame could not be shipped to site as a single piece. The 5 5/8 inches per 12 inches roof slope resulted in an approximately 15 feet 6 inches change in elevation from eave to peak.

To accommodate standard-length trucks and simplify construction, the design team spliced the frame beams at the peak using a field-bolted end plate moment connection and secured the frame-to-column connections with field-bolted cap plates.

The Gateway Ring forms the focal point of the 8th Street Gateway Park. This nearly two-thirds-mile loop includes approximately 880 feet of elevated trail built on a 520-foot centerline radius with a longitudinal slope. Two separate elevated trail structures—the East Gateway Bridge and West Gateway Bridge—span 372 feet and 508 feet, respectively, while the remainder remains at grade.

Each bridge features a long-span dovetail metal deck topped with a 6-inch concrete slab. Radiused wide-flange beams with composite studs connect to wide-flange crossbeams, providing lateral stability through moment connections to round HSS columns. Each elevated trail section includes a 7-foot cantilevered overlook for scenic views.

The truss bridges span approximately 110 feet across 8th Street on both east and west sides of the ring. Concrete abutments support the bridges, and columns slope transversely and longitudinally from pier caps atop nine 24-inch-diameter piers. Elevated trail columns rest on 36-inch-diameter drilled piers with pier caps.

The structures were designed in accordance with the American Association of State Highway and Transportation Officials (AASHTO) Bridge Design Specifications and the AASHTO LRFD Guide Specifications for the Design of Pedestrian Bridges. The design live load is 90 pounds per square foot, with wind loads determined per the AASHTO Bridge Design Specifications. Additionally, a 10,000-pound design vehicle was considered.

A challenge for the design team was determining how to deliver a structure meeting the architectural intent of the owner while being mindful of the budget constraints of the project. The design team went through a few different iterations of the structure before ultimately landing on the final design.

For the elevated trails, the architect envisioned a dynamic “skipping” effect, offsetting the inner and outer columns and using hollow tube beams for the edge supports. This offset created a structural challenge: diagonal members were required between columns to resist lateral forces, and intermediate transverse beams were needed to brace the diagonals against axial loads. Though technically feasible and allowing for a shallower composite deck, the approach significantly increased steel tonnage and overall cost.

Working closely with the architect and design team, Apex Engineers guided a value engineering review that resulted in the final solution, wide flange edge beams with wide flange crossbeam moment frames supporting a long span dovetail deck, balancing structural efficiency, cost, and the aesthetic vision.

The contractor identified the time and cost associated with corrosion protection as a challenge. The original specifications required a painted steel system; however, in response to the contractor’s concerns, the design team collaborated with them to identify a more economical and durable solution. Weathering steel was ultimately selected to provide long-term corrosion protection while maintaining the architectural intent and project budget.

ASTM A588 steel was specified for all wide-flange shapes and angles, and ASTM A847 was specified for rectangular and square hollow structural shapes. Because round HSS shapes are not available in a weathering steel grade, the round HSS columns supporting the elevated trail’s cross beams required a paint system for corrosion protection. All of the non-weathering material for the shear tabs and flange plates connecting the cross beams to the round HSS columns required a protective coating at the contact surfaces between the plates and the beam to prevent galvanic-like corrosion of the flange plates and shear tabs. All bolted connections utilize Type 3 bolts.

Thermal expansion also had to be considered during the bridge design process. Expansion joints and slip-joint beam connections were utilized at every other bay, approximately every 80 feet, to allow for thermal expansion along the elevated trail. Additionally, an expansion joint was specified at each end of the truss bridges, and baseplate connections allowing for thermal movement were provided.

Vibration control was a top priority for the structural team. Using AISC Design Guide 11: Vibrations of Steel-framed Structural Systems Due to Human Activity, the engineers determined acceptable frequencies for both the elevated trails and the truss bridges. Because AASHTO’s vibration criteria for pedestrian bridges are less strict, the team gained added confidence that their design went above and beyond to ensure a comfortable and safe experience for trail users.

The two truss bridges spanning 8th Street went through multiple design iterations before the final concept was selected. The architect initially proposed a 48-inch-deep plate girder half-through bridge with 8-inch-wide flanges. However, early analysis, combined with input from AISC’s National Steel Bridge Alliance, showed that this approach was not economically feasible within the architectural constraints—the flanges would likely have needed to be twice as wide as architecturally desired.

The next concept the team explored, and ultimately chose, was a half-through truss bridge. The team considered an arched truss, which ranged from 4 feet 6 inches to 10 feet between chord centers, but it did not match the architect’s design intent. Therefore, a shallow parallel chord truss was chosen.

Apex Engineers ran a dynamic analysis using RISA-3D to determine the bridge’s modal frequencies, which exceeded the requirements of LRFD Guide Specifications for the Design of Pedestrian Bridges.

The structural design of Bentonville’s 8th Street Gateway Park required a deep understanding of the project’s vision and close coordination with the full project team to create structures that blend with the landscape and elevate the visitor experience. Apex Engineers partnered with the project architects and contractor to select materials that naturally fit the surroundings while delivering a cost-efficient design that remained within budget. Ultimately, the park’s value will be reflected not by its engineering feats, but in how it brings people together, providing space for recreation, gathering, and meaningful connection to nature. ■

About the Authors

Aaron Kilgore, PE is an Associate & Project Manager at Apex Engineers and served as the Project Manager for this project. He brings extensive experience in the design of diverse structural systems across a wide range of construction types.

Austin Curnutt, SE, PE is a Senior Project Engineer at Apex Engineers and served as the lead design engineer for this project. He is dedicated to partnering closely with clients to develop innovative structural solutions that support their vision.

Bryce Crady, PE is the Principal & CEO of Apex Engineers and served as the stamping engineer for this project. With more than 20 years of structural engineering experience, he leads Apex’s three offices and guides projects nationwide.