With three girders already in place, a fourth girder is slowly lifted from the trailer.

Those who commonly use the Sellwood Bridge found it closed to all traffic, including pedestrians and bicycles, all day on Friday, May 20.

The barricades closed off the bridge at S.E. Tacoma Street promptly at 6 a.m., as construction crews began one of the final phases of construction.

Below the unfinished northern segment of the bridge at the east end, two large cranes sat ready to pluck concrete girders, one at a time, off semi-truck-trailer rigs, and place them on the waiting piers.

“During the day, we’ll see 13 concrete girders installed, across four spans of the east approach to the new bridge,” commented Multnomah County project spokesman Mike Pullen, as the cranes were just repositioning to lift the fourth girder into place.

T.Y. Lin International Bridge Engineer Eric Rau was also there at the worksite, and observed that these girders were cast months ago, at the same time others were manufactured that are already in use elsewhere on the bridge.

“Because the concrete has cured longer, each of these girders have a little bit of ‘camber growth’ [arching], which is accounted for in the design,” explained Rau.

Each of the “Bulb-I” precast concrete girders is 66″ deep, up to 110′ long, and weighs up to 75,000 pounds each, Rau said.

What is a “Bulb-I” precast concrete girder? “This indicates that, unlike the square geometries of steel I-beams and H-beams, the bottom is flared out — partially for strength, partially to provide for runoff keeping it from being a flat surface,” clarified Multnomah County Bridge Engineer Chuck Maggio.

Working in unison, and with amazing precision, the crane operators first lifted a girder off the trailer, swung it slowly over the railing, and then let it hover over its socket. Crews, perched on both ends of the piers, untangled the rebar coming up from the pier and the rebar protruding from the girder.

With the bearing pads in place, the girder was slowly lowered into its final position.

Is if performing an industrial ballet, each empty trailer drove off the bridge, and a loaded rig then pulled up into position, ready to be unloaded.

“It’s difficult to predict how long work like this will take, but this part of the project went well, and the Sellwood Bridge reopened to traffic at 8:15 p.m. the same evening,” Pullen later reported.

The final target date for all work on the bridge and its approaches to be completed and signed-off on is approximately Thanksgiving. THE BEE will continue to keep you up to date each month on the progress, until everything is done.