About eight inches per push—that is how the 3,400-ton Sellwood Bridge moved forward on Jan. 19 in Portland, Ore. The owner, Multnomah County, moved the 87-year-old, 1,100-ft-long steel truss 66 ft to the north using the span as a detour bridge, while a joint venture of Slayden Construction Group Inc., Stayton, Ore., and Sundt Construction Inc., Phoenix, builds a brand-new crossing over the Willamette River as part of a $299-million project.
The move occurred over 12 hours as 40 hydraulic jacks—each weighing 150 tons—lifted the 3400-ton steel span off its concrete columns. Ten 75-ton-capacity, digitally controlled hydraulic jacks inched it along tracks, moving the west end 66 ft and the east end 33 ft.