Home > Structures

A walk above

A walk above

Pedestrian bridges combine aesthetics and function with diverse designs.

Three pedestrian bridges highlighted in recent press releases — one under construction, one winning numerous awards, and one celebrating 25 years of service — reflect the creative and sometimes complex architectural and structural engineering involved in these signature structures that, according to LMN Architects, “elevate the pedestrian experience.

The Grand Avenue Park Pedestrian Bridge, which is establishing a new connection between the uplands Grand Avenue Park and the developing Everett, Wash., waterfront district, integrates accessible pathways into a sloped truss, eliminating the need for an uphill elevator and saving significant costs.

Grand Avenue Park Pedestrian Bridge, Everett, Wash.

Elevating utilitarian infrastructure to a thoughtfully designed community asset, the Grand Avenue Park Pedestrian Bridge highlights the value of rethinking public realm design. The bridge will transform the Everett waterfront, establishing a new connection between the uplands Grand Avenue Park and the developing waterfront district. The project will fulfill a decades-long goal for a convenient, non-motorized passage to the waterfront, which has grown to feature a 66-acre mixed-use development, the Everett Farmer’s Market, and the largest public marina on the West Coast.

The challenge for this project was how to resolve essential engineering infrastructure and transportation functions as seamlessly as possible. By deconstructing the elements of the project — functional, aesthetic, and environmental — and reimagining the parts, the design team developed a solution that preserved the view while greatly minimizing the intervention into the steep, 75-foot-high hillside. The new design integrates accessible pathways into a sloped truss, eliminating the need for the uphill elevator and saving significant costs.

Two ramps act as switchbacks to reduce the grade change and frame a series of dramatic views to Whidbey Island, the waterfront, and the Olympic Mountains. The ramps bring pedestrians through a varied sequence of spaces that interact with the structure, beginning above, then cantilevered outboard over the highway, and finally bringing them within the truss itself.

Along the pathway, a sequence of viewing platforms offers multiple experiences of the surrounding landscape. Resembling a railroad overpass, the weathered steel trusses of the bridge’s frame have been strategically positioned to echo the ramp volumes and sectioned over the active railway to allow for ease of installation during construction. Stormwater overflow piping — the initial impetus for the project — all but disappears beneath the pathway, reinforcing the bridge’s ability to elegantly solve simultaneous challenges. Hillside stormwater and sewer lines will also be replaced as part of the project, and the potential for a future water main crossing is incorporated into the bridge design.

While the project is driven by performance and practicality, the design affords opportunities for artful intervention. Custom-designed aluminum panels serve triple duty as safety rails, lighting reflectors, and visual elements. The panels feature a waterjet-cut geometric pattern that is as minimal as possible at eye level to facilitate views, while becoming denser in proximity to pathway lighting where it serves as a reflector. The geometric pattern is repeated on the base of the tower where it is sandblasted into the concrete to further animate the structure. By embracing a creative pragmatist approach, the solution addresses both functional and aesthetic demands, weaving urban infrastructure into the life of the city and becoming a catalyst for continued community revitalization. The $19.3 million project is anticipating completion in 2019.

The project team includes LMN Architects (design architecture), Interwest Construction, Inc. (general contractor), KPFF (prime consultant, structural engineering, civil engineering, construction support), McMillen Jacobs Associates (civil engineering), Tres West Engineers, Inc. (mechanical engineering), Stantec (electrical engineering), HWA GeoSciences, Inc. (geotechnical engineering), The Greenbusch Group, Inc. (vertical transportation), Landau Associates, Inc. (environmental engineering), Ott Consultants (constructability review and construction scheduling), KBA (construction management services), and City of Everett Parks & Recreation (landscape).

Idaho Ave. Pedestrian Overcrossing, Santa Monica, Calif.

The spiraling Idaho Avenue Pedestrian Overcrossing Bridge, named California’s Outstanding Bikeway and Trails Project for 2017, takes people from the cliffs of Palisades Park down to the Pacific Ocean.

TRC Companies Inc. announced that the Idaho Avenue Pedestrian Overcrossing Bridge was named California’s Outstanding Bikeway and Trails Project for 2017. The award for the spiraling footbridge, which takes people from the cliffs of Palisades Park down to the Pacific Ocean, was given by the American Society of Civil Engineers. TRC served as construction manager on the project.

The new overcrossing replaced the original 1957 structure, which was starting to deteriorate. The project included construction of a 1.2-mile bike path and jogging trail. The work was part of a larger $20 million project in which TRC assisted the City of Santa Monica in rebuilding the California Incline Bridge, which connects Santa Monica to the Pacific Coast Highway. The original 750-foot bridge was constructed in the 1930s and needed to be brought up to current seismic standards.

For motorists driving up the California Incline, the V-shaped pier of the overcrossing frames stunning views of the Santa Monica Pier, the beach, and the Pacific Ocean.

The Idaho Avenue Pedestrian Overcrossing has received numerous awards, including a 2018 Engineering Excellence Honor Award from the American Council of Engineering Companies of California and the 2017 International Bridge Conference Arthur G. Hayden Medal.

Denver International Airport Passenger Bridge

In June, the Denver International Airport celebrated the 25th anniversary of construction of its Pedestrian Bridge, one of only two of its kind in the world today. The bridge connects the main terminal with concourse A, with a security portal on its lower deck and international customs accessed on its upper level. Constructed in 1993 to offer a pedestrian alternative to the airport’s inter-terminal train system, the bridge was a widely acclaimed design feat for its time.

“This project was incredibly sophisticated. This was the first time a passenger structure had been built in the world large enough to allow for planes to travel underneath. And at a length of 365 feet, we designed it so two planes could pass under it side-by-side,” said Luis O. Acosta, the architect of record who led the project’s design.

Denver International Airport’s Pedestrian Bridge, constructed in 1993, is a freestanding 40-foot-wide, 365-foot-long structure with enough clearance to allow two planes to travel underneath side-by-side.

Built as a freestanding structure, the 40-foot-wide, 365-foot-long passenger bridge was designed by LOA Architecture (previously Luis O. Acosta Architects). Other design team members included the structural engineer and prime consultant LONCO (now operating as Benesch), mechanical engineer Behrent Engineering, and electrical engineer Roos/Szynskie. The bridge was built by M.A. Mortenson Company. The project’s construction took less than 12 months; it is currently the longest free-span airport bridge in the U.S.

The bridge, not originally included in the airport’s master plan, was added after the main terminal and concourse A had already been constructed. Since the two buildings did not align at the same height, and were not designed to connect, the architects were tasked with the further challenge of creating an arc that would be both structurally sound and visually appealing. A further challenge to the project was FAA restrictions that required clearance distances from the top of the runway to the underside of the bridge as well as consideration for the bridge’s deflection under various loading conditions.

Further challenges the team had to address included creating a structure that did not allow icicles to form, which could cause damage to planes passing underneath, and supporting the two-level bridge when the underground passenger train ran directly underneath causing regular vibrations.

An all-glass curtain wall system encloses the bridge, providing a panoramic view of Colorado’s diverse environments with the Rocky Mountains visible to the west and the plains to the east.

“This team did a wonderful job of creating something never before built, in a condensed timeframe to support Denver’s globally renowned airport. That the project has remained virtually untouched since its construction is a real testament to the talent that brought this project to life,” said Brian Holland, with Mortenson Construction.

Information provided by LMN Architects (https://lmnarchitects.com); TRC  (www.trcsolutions.com); and LOA Architecture (www.loaarchitecture.com).