A major project milestone occurred in late October when the first concrete pour was completed for one of the main steel arch spans of the new Sellwood Bridge in Portland, Oregon. Eleven pours will be required as the concrete deck is added to the spans. As planned, the first concrete pour lowered Span 3 by six inches in a matter of hours, as the weight of the concrete loaded the arch. When concrete is added to Span 5 to the east, it will cause Span 3 to rise several inches, as the arch spans transfer the load. The sequence of adding the concrete deck to the arch spans is a mathematical puzzle that engineers have worked out in great detail. One or two deck pours are planned each week through early January, while the installation of rebar on the main arch spans continues in preparation for deck pours.
Photo and info credit to SellwoodBridge.org