Markets:Bridges & Interchanges
“Sundt came up with a very innovative idea that no one at the County had thought about and that was how can we shorten the construction time save money and still keep the bridge open and they came up with this very bold idea to actually move the steel truss that carries most the Sellwood Bridge and actually move it out of the way and then demolish the remaining supports in the river and this would give them the space to build the new bridge in one phase instead of two phases which was the old way we thought it would have to be done and this was a very innovative idea. The idea of actually moving something that is 1,500 feet long and pushing it north to put it on a new alignment was a very innovative, bold idea and because of that there was skepticism about it. I don’t think anything that long had ever been moved in that particular way and having a good visual explanation of how that would happen was very key in selling the idea to our leaders who had to feel comfortable with it and then the neighbors that lived around it who are affected by it. Having the visuals we actually had an animated piece that would show the different phases and you could watch it in just a minute to understand it and it was really helpful.”
Mike Pullen, Public Information Officer, Multnomah County, Oregon
This project, for Multnomah County, involved reconstructing the 2,000-foot-long, aging Sellwood Bridge over the Willamette River. Designed as an open steel deck arch structure, the new bridge complements its surroundings while providing ample space for all modes of travel. There are two vehicle lanes in each direction on the west end, which narrow to one lane in each direction on the east end. In addition, there are two, six-foot-wide bike lanes and two, 12-foot-wide sidewalks.
Sundt and its joint venture partner used a "shoofly" (detour) approach to complete this project. The team lifted the old bridge deck and truss with hydraulic jacks and moved it to one side, then placed it on a set of temporary piers and connected it to temporary approach spans so traffic could use it while the new bridge was constructed. Using the detour bridge allowed the team to close the bridge for only 20 days, well inside the 30 days called for in the contract.
Time- and cost-savings began before the first components of the old bridge were removed. The team used Building Information Modeling and a sophisticated video presentation to develop and propose a faster, safer and less expensive method for reconstructing the bridge than was originally called for in the project’s Environmental Impact Statement. The bridge translation approach shortened the schedule by a year and reduced the cost to the owner by more than $5 million.
In order to place the bridge's concrete deck, specifications called for less than a 30 percent chance of rain before, during and after the pour, which required a 12-hour window of good weather. Finding such a window in Portland during the winter was tough, requiring pours to start as early as 3 a.m. The specifications additionally required the concrete to be above 60 degrees, posing a problem when temperatures dropped into the 20s. Much of the concrete had to be covered and heated to remain within specifications. Crews had four bent pours that took more than 30 hours each. The nine concrete deck pours required extensive coordination among the supplier, pump subcontractor, joint venture quality control, Multnomah County quality assurance and Oregon Department of Transportation inspection teams.