Seismic Performance and Fragility of Retrofitted Reinforced Concrete Bridge Columns to Long-Duration Earthquakes
Adam Phillips, PI
Chris Motter, Co-PI
Long duration earthquakes are characteristic of the Cascadia Subduction Zone, which has the potential to generate a Magnitude-9.0 earthquake with strong shaking in Washington, Oregon, northern California, and Alaska. The proposed research is focused on characterization of the probability of failure of retrofitted bridge columns due to fatigue fracture of reinforcement under long-duration earthquakes. The proposed research will include the formulation of fatigue fracture models based on actual earthquake strain histories, as previous research on fatigue modeling of reinforcement has used idealized reversed cyclic loading histories. Ongoing research by the PIs on this topic has generated test data for legacy grade 40 reinforcement, typical of 1950s-1970s bridges. The proposed research will include additional testing of modern grade 40 and grade 60 reinforcement to better characterize the influence of earthquake cycle content on fatigue life. Nonlinear time history analyses, incorporating the improved fatigue fracture models, will be conducted for a range of bridges subjected to Cascadia Subduction Zone demands, and results will be used to develop failure fragilities.