November 2009
- Engineers continue to test different designs to strengthen the unique columns of the Aurora Bridge.
The SR 99 Aurora Bridge is vulnerable to earthquake damage and the columns, trusses, crossbeams and girders need to be strengthened. Traditionally, WSDOT has used round steel jackets to strengthen bridge support columns. However, round steel jackets would obscure the Aurora Bridge's special cruciform ("+" shaped) columns. The bridge is on the National Register of Historic Places and is a City of Seattle Landmark.
WSDOT engineers are studying different techniques to strengthen the bridge support columns while also preserving the unique appearance of the landmark.
Why is WSDOT
strengthening the Aurora Bridge columns against earthquakes?
This bridge is a key route for commuters and freight and carries about 80,000 vehicles a day heading to and from Seattle. The bridge opened in 1932, when earthquake design standards were not as rigorous as they are today.
Seismic studies in 1995 and 2001 outlined improvements that would strengthen the bridge to better resist earthquake damage.
Previous projects strengthened other parts of the bridge, including installing new expansion joints, adding bearings that absorb movement and replacing some trusses ($7.3 million), and adding restrainers ($2.1 million) to better withstand earthquakes.
This next phase targets 18 of the bridge's 48 support columns, as well as trusses, crossbeams and girders.
The End Result
When the project is completed, the columns supporting the Aurora Bridge will better withstand earthquakes and resist damage. Trusses, crossbeams and girders also will be better able to resist damage and make for a stronger, safer bridge.
This will keep traffic flowing on this key route into Seattle and protect nearby residences, businesses and traffic from damage if the columns were to crumble or fail during or after an earthquake.
Project Benefits
Earthquake-resistant bridge columns will help prevent the collapse of the Aurora Bridge. The improved columns also will be less likely to crumble, split or crack in ways that would make the bridge vulnerable to collapsing later or showering concrete onto businesses, residences and traffic below. Stronger trusses, crossbeams and girders also help the bridge resist earthquake damage.
These benefits protect drivers and nearby residents and keep traffic flowing on this key route into Seattle.
What is the project timeline?
June 2007 - Winter 2010: Project design and testing
Winter 2010: Advertise for construction
Spring 2011: Award contract
Summer 2011: Construction begins
Fall 2012: Construction complete
Financial Information
Project budget: $9.3 million, including federal funds and gas taxes
How can I get more information?
Contact:
Mike Murphy
WSDOT communications
206-440-4699
murphym@wsdot.wa.gov
Hung Huynh
WSDOT project engineer
206-440-4311
huynhh@wsdot.wa.gov
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