Behavior Of Carbon Fiber Reinforced Polymer Jacket Retrofitted Reinforced Concrete Bridge Columns In Cascadia Subduction Zone Earthquakes

Bridges built before the early 1970s contain seismic vulnerabilities not accounted for in older design codes. Retrofitting with carbon fiber reinforced polymer (CFRP) jackets is a commonly implemented strategy to address the seismic vulnerabilities present in previously constructed bridges. Previous research has not specifically studied behavior under Cascadia Subduction Zone (CSZ) demands. Six CFRP jacket retrofitted concrete bridge columns were designed, constructed, and tested under demands based on CSZ earthquakes. Five of the six test columns were nominally identical to previously tested steel jacket retrofitted columns to allow for comparison between the two retrofit methods. Detailed test results are provided. Strength degradation in five of the six columns was caused by fatigue fracture of longitudinal reinforcement. The sixth column underwent degradation due to plastic hinging above the jacket. Using experimental results, a model was developed to estimate the load-deformation response and fatigue fracture of longitudinal reinforcement in CFRP jacket retrofitted reinforced concrete column. The model was validated with test data. Single degree of freedom nonlinear time history analyses were conducted using the model. Site-specific Magnitude-9.0 Cascadia Subduction Zone simulated ground motions for western Washington State were used. Fragility relationships that provided the probability of lateral failure were developed for a practical range of bridge column parameters and bridge periods, strengths, and locations.