From Mike Murphy to QACC:
The Washington State Department of Transportation (WSDOT) is movingforwarding with design of a safety project to seismically retrofit theState Route 99 Aurora Avenue Bridge in Seattle.
The historic Aurora Bridge, which opened to traffic in 1932, isvulnerable to earthquake damage. Seismic studies in 1995 and 2001outlined improvements that would strengthen the bridge. In 2005 WSDOTmade earthquake safety improvements on the bridge by installing newexpansion joints, adding bearings that absorb movement and replacingsome trusses. This next phase, set to begin construction in summer2011, targets the bridge’s support columns. Construction is expectedto be completed in fall 2012.
Traditionally, WSDOT seismically retrofits bridges by installing steeljackets around the columns that allow them to better withstandearthquakes. However, round steel jackets would obscure the AuroraBridge's special cruciform ("+" shaped) columns.
Instead, WSDOT plans to install a fiber reinforced polymer (FRP) wraparound the columns. Like steel jackets, this unique wrap would allowthe bridge to better resist earthquake damage. Crews also will put alayer of concrete over the fiber polymer and paint it the same coloras the surrounding concrete. Other structural safety improvementsinclude reinforcing the steel spans at the south end of the bridge,installing steel bars or FRP wrap on the longitudinal concrete girdersand installing FRP wrap on the crossbeams.
In addition to improving safety, the goal is to change the appearanceof the bridge’s unique architecture as little as possible.
Because the Aurora Bridge is on the National Register of HistoricPlaces and is a City of Seattle Landmark, our design must first beapproved by the Seattle Landmarks Preservation Board.
WSDOT design engineers will update the Architectural Review Committeeon the status of the project on Friday, April 30, 2010. The meetingbegins at 8:30 a.m. and will be held in room 4070 (40th floor) of theSeattle Municipal Tower at 700 Fifth Avenue. It will be open to thepublic and you are invited to attend.
More information this project can be found atwww.wsdot.wa.gov/projects/sr99/AuroraBridgeSeismicRetrofit.
If you have any questions or comments, please don’t hesitate tocontact me directly.
Mike Murphy, WSDOT Communications, 206-440-4699, MurphyM@wsdot.wa.gov