The Cascadia Subduction Zone earthquake—whenever it occurs--is expected to devastate the Pacific Northwest region and destroy the Burnside Bridge in Portland, Oregon. Expert analysis indicates that the bridge is likely to collapse in a manner that would block north-south ship traffic in the Willamette River. Because two-thirds of the Burnside is over land on either side of the river, a bridge collapse would mean that the adjoining roadways would be blocked as well, leaving people on both sides of the river stranded. Worse, the five-lane roadway is also a designated official “regional lifeline route,” intended to carry first responders and needed supplies during emergencies. If the bridge were to fail, that lifeline route would be cut off. 

Because the Burnside Bridge plays such an important role in the life of our city, transporting more than 40,000 vehicle and 2,000-plus pedestrians and cyclists each day, Multnomah County engineers are undertaking a major bridge improvement project. In an effort to generate imaginative ideas for the bridge and spark a public conversation about what the potential for the redesigned structure, they enlisted Professor Jeff Schnabel and a class of Portland State University Master of Architecture students to design concepts for the Burnside. 

Citing examples of multi-purpose bridges such as the Ponte Vecchio in Florence, Italy, Schnabel posed the questions, “How do you make a bridge that meets the needs for right now, and what role does it play post-earthquake? How do you design a structure that is at once functional, beautiful, and iconic?” 

County officials asked for innovative designs that were multimodal, accommodating cars and transit vehicles as well as improving the experience for cyclists and pedestrians, Schnabel said. “The students also looked at how to integrate the bridge connections with the green spaces on either side in order to enrich that bike and pedestrian experience.” 

Because the County is still determining what type of bridge to use, the students’ proposals ranged from operable to fixed bridge designs, keeping in mind how these would impact the urban fabric. For those who went with a fixed bridge option, they needed to find ways to address the issue of increased underbelly. Others went with a movable bridge, with a vertical lift or double-leaf Bascule mechanism; with this option, students had to contend with potential interruptions to traffic flow.

Some of the designers created dramatic light features in their bridges that could act as beacons, while others incorporated digital art panels that could convert to emergency messages. Creating modes of access to water-based transportation was an important part of students’ designs as well. 

The idea of a bridge that serves multiple functions was particularly compelling. One such proposal suggested that the bridge could be used as scaffolding—extending alongside the unreinforced masonry buildings at the ends of the bridge and providing structural support. That same scaffolding would also create temporary market space on either side beneath the bridge, and places for emergency services to be offered. 

Throughout the design process, students presented their design proposals to bridge engineers and officials at Multnomah County and got their feedback. 

County officials didn’t always agree with the students’ proposals—financial and practical constraints meant that sometimes the students’ designs were nixed. “But that was really the best part of the studio--there was a dialogue,” said Schnabel. “Naturally, the County representatives were open to new ideas, but they had a clear perspective on their needs for the bridge, and as a result the students confronted more criticism than they would get in a traditional academic setting. But pedagogically that was a valuable experience. They had to come up with brilliant ideas that would also resonate with the client and meet their practical requirements.”

The students’ designs were shared with the public at Visualizing a New Burnside Bridge, an open house event on Wednesday, May 15, 2019, from 5pm to 8pm, in Shattuck Hall, the home of the School of Architecture. The County is seeking the input of community members.