When the Barbara Walker Crossing was first conceived in 2012, its primary function was to spare hikers and runners on Portland’s Wildwood Trail the hassle of avoiding traffic on busy West Burnside Road.
It became a testament to aesthetically conscious architecture, blending utility and beauty for a community that valued (and demanded) both.
Completed in October 2019 and inaugurated the same month, the bridge is a 180-foot-long pedestrian walkway that is planned to be curved and designed to blend into the surrounding forest.
It was fabricated off-site by the now-defunct Portland Supreme Steel Company, cut into three main sections, and then trucked to the site.
Meeting the visual and architectural requirements meant using materials that would achieve all of the project’s highly unique goals, both artistically and structurally.This means using pipes – in this case 3.5″ and 5″.corten (ASTM A847) structural steel tubing designed for structures requiring welded or bolted connections.Some pipes are exposed (another key Corten feature) and some are painted green to match the forest canopy.
Ed Carpenter, a designer and artist specializing in large-scale public installations, said he had several goals in mind when he conceived the bridge.Among them, the bridge should be integrated into the forest context, which is a continuation of the feeling and experience of the trail, and should be as delicate and transparent as possible.
“Because one of my most important design goals was to make the bridge delicate and transparent, I needed the most efficient materials and the most efficient structural system possible—so, three-chord trusses,” says Carpenter, who is also an outdoor enthusiast. .Running on Portland’s vast trail system for over 40 years.”You could build it out of other materials, but steel pipes or pipes are just the logical choice.
From a practical construction standpoint, achieving all this is not easy.Stuart Finney, a structural engineer in the Portland office of engineering firm KPFF and a former bridge project manager, said successfully welding all the components at the TYK junctions where all the supporting pipes meet was probably the most difficult.One aspect of the whole effort.In particular, all the different angles required for different types of welds, such as fillet welds and grooves, created serious challenges for the construction team.
“Essentially every joint is different,” says Finney, who has practiced the craft for 20 years.”They had to make every joint perfect so that all these pipes were joined together at one node, and they could get enough welds around all the pipes.
The Barbara Walker Crossing pedestrian bridge spans Portland’s high-traffic Burnside Road.It went live in October 2019.Shane Bliss
“Welds have to be completely transformed. Welding can indeed be one of the most complex parts of manufacturing.”
Ferry’s namesake, Barbara Walker (1935-2014), has been a mainstay of Portland’s conservation efforts for years, and she’s a bit of a force of nature herself.She has played an active role in numerous public projects in Portland, including Marquam Nature Park, Pioneer Courthouse Square and Powell Butte Nature Park.She also tirelessly advocated what became known as the 40-Mile Loop, which included the Wildwood Trail and Bridge.
Just as Walker raised about $500,000 from the public for Pioneer Courthouse Square ($15 per paving stone), the nonprofit Portland Parks Foundation raised $2.2 million from about 900 private donations to help fund the bridge.The City of Portland, Portland Parks & Recreation and other entities contributed the remainder of the approximately $4 million cost.
Carpenter said juggling the many voices and voices on the project proved challenging, but well worth it.
“I think the most important experience is the great community collaboration, the great pride, and the great engagement — people are paying for that,” Carpenter said.”Not just individuals, but cities and counties. It’s just a great collective effort.”
Finney added that he and his team, and the manufacturers responsible for bringing the designs to life, had to overcome many of the challenges in the 3D modeling they did, simply because of all the intricacies of the joints and fittings.
“We’re working with our detailers to make sure all the models line up because again, there’s no room for error with many of these joints because of the complexity of the geometry,” Finney said.”It’s definitely more complicated than most. A lot of bridges are straight, even curved ones have curves, and the materials are relatively simple.
“Because of that, there’s a lot of little complexity that comes up in the project. I would definitely say it’s more complex than a regular [project]. It takes a lot of work for everyone to get this project to fruition.”
However, according to Carpenter, among the key elements in the bridge’s complexity, what gives the bridge its overall effect is the curved deck.Is it worth the trouble to do this?Mostly, yes.
“I think good design usually starts with practicality and then moves on to something more,” Carpenter said.”That’s exactly what happened on this bridge. I think for me, the most important thing is the curved deck. In this case, I really don’t feel good about the candy bar because the whole path is so undulating and bends. I just don’t want to make a sharp left turn across the bridge and then make a sharp left turn and keep going.
The Barbara Walker Crossing pedestrian bridge was fabricated off-site, split into two main sections, and then trucked to its current location.Portland Parks Foundation
“How do you make a curved deck? Well, it turns out, of course, a three-chord truss works really well on a curve. You get a very favorable depth-to-span ratio. So, what can you do with a three-chord truss to make it elegant and Beauty, and refer to the forest in a way that makes it seem as if it couldn’t be anywhere else? Start with practicality, then move toward — what’s the word? — toward fantasy. Or from practicality to imagination .Some people might do it the other way around, but that’s exactly how I work.”
Carpenter especially credits the KPFF crew for giving him some inspiration he needed to project the pipes beyond the deck, which gave the bridge an organic, emergent feel from the forest.The project took about seven years from start to grand opening, but Finney was delighted to have the opportunity to be a part of it.
“It’s nice to have something to offer this city and be proud of it, but also nice to tackle a neat engineering challenge,” Finney said.
According to the Portland Parks Foundation, about 80,000 pedestrians will use the pedestrian bridge each year, saving the trouble of crossing a section of road that sees about 20,000 vehicles a day.
Today, the bridge continues Walker’s vision of connecting Portland residents and visitors to the beauty of the surrounding natural landscape.
“We need to provide urban people with access to nature,” Walker (cited by the World Forestry Center) once said.”The excitement about nature comes from being outdoors. It cannot be learned in the abstract. By experiencing nature firsthand, people have the urge to become land stewards.”
Lincoln Brunner is editor of The Tube & Pipe Journal.This is his second stint at TPJ, where he served as editor for two years before helping launch TheFabricator.com as FMA’s first web content manager.After that very rewarding experience, he spent 17 years in the nonprofit sector as an international journalist and director of communications.He is a published author and has written extensively on various aspects of the metal fabrication industry.
Tube & Pipe Journal became the first magazine dedicated to serving the metal pipe industry in 1990.Today, it remains the only publication in North America dedicated to the industry and has become the most trusted source of information for pipe professionals.
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