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Bridge Building The Portland Way

By TJ McCueWednesday, June 11, 2014
3D Design, Construction, Design, Engineering, Infrastructure

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Moving a large object, for instance, a 40 foot wooden beam, might involve some brainpower, but not too much. Sliding a 1,000-foot long bridge requires a fair amount of genius. Not only did Sundt Construction propose the novel idea of temporarily moving the old Sellwood Bridge in Portland, Oregon, but they did so in a way that allows them to build the new bridge in one stage.

The contractor is able to save Multnomah County millions of dollars and months of schedule time.  Ted Aadland, Area Manager for Sundt Construction on the Sellwood Bridge Project, explains that 3D visualizations made with a variety of Autodesk programs illustrated this concept to county decision makers, and then the public.  You can take a look at the visualizations that were used to explain how it could work, and it worked perfectly: The bridge was successfully moved in one day in January 2013.  It is one of the longest structures ever moved. The project is officially a joint venture between two contractors: Slayden and Sundt.

3DRV had the opportunity to take a close look at a typical day of bridge building. Mike Pullen, Multnomah County spokesperson, spent some time showing us around the project and explaining the different aspects. In addition to the bridge move process, most people in the Portland region know that the old Sellwood Bridge being replaced was a REALLY bad bridge.  Every bridge in the US has a sufficiency rating between 1 and 100, with a high score being best.  The Sellwood Bridge earned the high score of 2. Yes, you read that right, two rating points.  Out of 100 possible. Ouch. The County and the community knew something had to be done and they moved pretty quickly. 

The main flaws for the bridge revolved around severe cracks in its concrete supports that was plagued by an ongoing landslide, or at least land-shifting. Dana Tims, reporter at the Oregonian, has a great post (from 2013) on why the bridgework is also protecting the slope from future slides.

But the old bridge was also very un-Portland-like – given that this is one of, if not the most bike and pedestrian-friendly city that I have experienced in the USA. So this bridge was not truly keeping up with the times, so to speak. It had very narrow traffic lanes, a skinny sidewalk, and a weight limit that prohibits buses and trucks. The new bridge will address all these problems and will have the greatest amount of space for bicyclists and pedestrians of any bridge in the “City of Bridges.” Most residents will consider it a "green" bridge because it promotes bikes and peds and transit instead of just creating more lanes for cars. Plus, it links to riverside bike trails on each side of the river.  It now seems to fit Portland's active transportation reputation. 

On a final note, moving a large heavy object often requires lubrication, but what do you use when you are over a well-loved and highly protected river? You find the most eco-friendly solution you can – they used Dawn dishwashing detergent to “grease the skids” and move the enormous structure. So now the Sellwood Bridge is squeaky clean, too.

For more information, here is the official county page, plus a cool documentary video. You can keep up with Sundt’s reports on their blog here.

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