SEATTLE â All lanes of the State Route 99 Aurora bridge are scheduled to reopen in time for the Wednesday morning commute, as workers completed an emergency repair to a damaged support beam under the southbound lanes.
On Thursday night, Oct. 31, the Washington State Department of Transportation reduced the bridge to two lanes in each direction to give contractor crews room to fix the beam, also known as a stringer, which had corroded and dropped about half an inch.
A stringer is a steel piece that runs lengthwise under a bridge deck. It is riveted or bolted to beams with steel plates to carry the weight of the deck. WSDOT structural engineers discovered the damaged stringer under the far right southbound lane on Oct. 27 during a scheduled inspection.
âThis was a complicated repair because the contractor was working with a stringer that was still holding a section of bridge deck,â said WSDOT Assistant Regional Administrator Messay Shiferaw. âWe needed to lift the closed part the deck with additional steel to alleviate pressure from the stringer, repair the connecting steel and bolt it all back into place while still supporting the concrete deck.â
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Shiferaw credited the expertise of contractor Guy F. Atkinson Constructionâs steel workers and painters for the quick repair. The contractor crews removed paint from the damaged area, replaced connecting plates and repainted the section to protect it from corrosion. WSDOT inspected and approved the completed work.
The bridge, which was built in 1931, has 13 stringers supporting each section of the structure. When the damaged stringer shifted, nearby stringers carried the weight from the corroded piece.
Earlier this fall, crews finished painting the trusses that support the bridge deck, but did not work in the area of the damaged stringer. That area was painted as part of a 2016 project.
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