By Paul Tarricone
Photo: Brad Nelson
When LD+A says bridge, you probably think vehicular. Most of the bridge lighting coverage that rolls across our pages touches on long-span structures that carry cars and are often well-recognized in their communities. The simple pedestrian bridge can sometimes get lost in the traffic of these more glamorous transportation projects, but in 2017, the two footbridges featured here scored IES Illumination Awards of Merit for their design inspiration. One resides in a suburban setting in Irvine, CA, while and the other graces a rural area of Edmonton. Both are welcome additions to the neighborhood aesthetic.
IRVINE IN LIVING COLOR
Unless you’re famished and eagerly eyeing your morning bowl of oatmeal, the color beige doesn’t usually make one’s heart flutter. Recognizing this conundrum, the City of Irvine, CA, ordered up a splash of color for a 282-ft pedestrian/cycling bridge that links several family-oriented neighborhoods to an extensive park and trail system. “The beige dominance in Irvine is driven by the primary developer, which has a tendency to build Italian and Spanish style stucco homes with a relatively plain color palette in the white/beige realm,” explains Brad Nelson, director-lighting, StudioK1, Irvine. The influence of this particular developer “is very apparent as one drives around the city.”
Also predictable are Irvine’s existing pedestrian bridges, which connect a series of bike paths/sidewalks/trails to these neighborhoods. Says Nelson: “They’re are all very traditional truss bridge structures created from square tube steel to look like train bridges.”
However, when a different developer was tapped to build new neighborhoods and a footbridge, “their goal was to stand out and draw attention to the differences of this area from the rest of Irvine. To do this, the team started with a very different shape and new materials, and then added lighting and color, none of which the other bridges have. The team then addressed the various view angles of the bridge—as it appears to vehicles, and also to bridge-goers—with the intent of keeping it simple for roadway traffic but playful for the users.”
The new bridge’s distinguishing feature is a series of “gateways”—essentially arches—that increase in size and build excitement for those traveling toward the park. The five gateways create a clean architectural aesthetic in which the support structure for the 11-ft wide concrete slab and steel girder bridge is concealed. Starting at 30-ft tall and 3-ft long, the gateways progress to 46-ft tall and 12-ft long at the south end of the bridge. The total length from the first gateway to the last is 282 ft with an open span of 165 ft in the center over the nine lanes of traffic below.
The interior surfaces of the gateways provided the opportunity for a less traditional approach to accent lighting, notes Nelson. Linear LED fixtures (Lumenpulse) are kept out of view and positioned in the gap between the guardrail and gateway so they can light the entire interior of the frames. “With the light washing the inside faces, the square design created a ‘hard stop’ for the lighting, which increased the pop by leaving the rest of the gateway dark,” says Nelson. “Then through programming, each gateway can take on its own personality through different colors, or they can all be themed together for holidays and special occasions.”
The exterior surfaces perpendicular to the roadway are uplit from ground level with simple warm white LEDs to provide a soft accent. “We wanted to provide a point of interest to those in traffic without providing a distraction that may have been caused by color. Many of the adjacent trees were also uplit with warm white helping the bridge settle into place amongst the landscape built up to support the ends of the bridge,” Nelson adds.
Like the existing pedestrian bridges, the new structure crosses over the heavily trafficked Irvine Boulevard. As a result, the developer and construction team devised a traffic management plan that would not inhibit the average daily use of the boulevard during construction. “To do this, the team elected to not rip up any pavement below which meant that the bridge would be entirely self-contained. All of the utilities were to be routed through the bridge’s structure, so conduit for power and control were coordinated with the steel that supports the bridge. Transformers were located inside the gateways with access panels so that the tiny low voltage steplights could be fed appropriately.” These steplights, which are integrated into the guardrail panels, were crucial in meeting the 1 footcandle minimum of the Irvine Uniform Security Code for illumination on the bridge surface. Finally, a local DMX controller allows for color changes to accommodate any event or holiday.
ASSIMILATION IN EDMONTON
When there’s no chance to stand out, it’s best to fit in. That was the guiding design principle for the Terwillegar Footbridge in Edmonton, Alberta, where a minimalist design for this river crossing makes a statement without detracting from the surrounding scenery.
For this 860-ft-long stressed ribbon bridge, the design team from locally based Stantec Consulting Ltd. had to grapple with three technical challenges. First, “poles and bollards were not permitted due to the architectural and structural guidelines,” says Stantec Vice President Glenn Stowkowy. “The client [the City of Edmonton] wanted light fixtures to be ‘part of’ the bridge design.” Integrated handrail lighting was also prohibited due to potential dynamic structural forces experienced by the handrail. “The bridge deck itself actually flexes as people walk on it,” explains Stowkowy. The solution was to mount LED lights at the base of the guardrail between the vertical railings at regular intervals. “Placing the lights here also makes the design more aesthetically pleasing,” notes Stowkowy. The LEDs also cast perpendicular lines of light across the walkway to reduce the perceived length of the bridge.
Second, pedestrian safety was a focus, as the footbridge connects to an existing river-valley trail system. Vertical illuminance was to be maintained at 1-2 fc to “identify the body and face of pedestrians,” says Stowkowy. Since the bridge is located in a remote area and not near an urban environment or commercial area, Stantec designed for “Medium Pedestrian Conflict Areas” per the IES RP for roadways. The solution was 4-W, 850-lumen LED adjustable spotlights with a 40-deg beam spread mounted approximately 2 ft above the base of the bridge. Custom vertical spread lenses were added to the luminaires to increase the vertical light distribution for pedestrians. “This vertical spread lens distributed the lighting without aiming lights upward,” says Stowkowy, “thereby minimizing glare and providing visual comfort.”
The third challenge was to identify lighting solutions that would create a visual reference point for the bridge and highlight its four canopies. Decorative RGB LED floodlights installed on the structural supports of the bridge provide colorful lighting along the concrete façade. DMX control provides the client with custom scenes. Finally, to complete the aesthetic effect, the canopies are illuminated by floodlights mounted to each canopy’s structural member.