In 1991 WSDOT began a seismic retrofit program for state bridges that continues today. WSDOT’s primary method for retrofitting concrete bridge columns is steel jackets. The USGS recently released updated hazard maps that require structural design in Western Washington to plan for increased levels of seismicity, reflecting the potential for the Cascadia Subduction Zone (CSZ) to generate large magnitude, long duration earthquakes. The ability of WSDOT’s bridge columns retrofitted with steel jackets to resist this increased earthquake hazard level is not well understood, and questions remain regarding the level of damage that would be sustained in a CSZ earthquake. If the level of retrofit is not sufficient to prevent collapse, the millions of dollars expended by WSDOT on retrofit will not deliver the intended results. This project will characterize the expected performance, ductility capacity, and collapse probability of steel jacket retrofitted bridge columns in CSZ earthquakes and will develop a simple tool that WSDOT can use to assess whether a standard steel jacket retrofit is adequate to resist a design level earthquake for each bridge column in its inventory.
Project Investigators:
Christopher Motter, Civil and Environmental Engineering, WSU
Adam Phillips, Civil and Environmental Engineering, WSU
Sponsor: WSDOT
WSDOT Technical Monitor: Bijan Khaleghi
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion: September 2021