Markets:Bridges & Interchanges
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.