Seismic performance and analysis of ductile composite-jacketed reinforced concrete bridge columns

This dissertation describes findings from a comprehensive experimental and analytical study on seismic repair and retrofit of model scale bridge columns using advanced composite-material jackets. This research comprises two different phases.; In the first phase of this study, fourteen half-scale squat circular and rectangular columns were tested for shear and confinement enhancement in a fixed-fixed condition. The experimental program included: three as-built columns, ten retrofitted samples, and one repaired column. The as-built columns failed in a brittle shear mode, whereas the jacketed samples underwent flexural failure modes with significant improvement in the column ductility. Other experimental results for 66 as-built, repaired and retrofitted circular and rectangular squat, columns were also collected from the literature. In addition to the experimental study, an object-oriented computer code (SHEAR), based on moment-curvature analysis, was developed to predict the seismic performance of all column data. For as-built columns, the code was used to evaluate different shear strength models. However, for jacketed column samples, the developed software was calibrated through a parametric study on two displacement models and six different concrete confinement models. Lastly, seismic retrofit design methodology was proposed for circular and rectangular squat shear-deficient columns.; In the second phase of this study, thirteen half-scale circular and square columns with insufficient lap-splice length were tested in flexure under lateral cyclic loading. The experimental program comprised three as-built samples and ten retrofitted columns. A brittle failure was observed in the as-built samples due to bond deterioration of the lap-spliced longitudinal reinforcement. The jacketed circular columns demonstrated a significant improvement in their cyclic performance. Yet, tests conducted on square jacketed columns showed a very limited improvement in clamping on the lap-splice region and for enhancing the ductility of the column. In addition, other experimental results for 11 as-built and retrofitted circular and rectangular columns with poor lap-splice details were collected from the literature. Another object-oriented computer code (LAP) was developed for predicting the behavior of the tested columns. The numerical model is based on a moment-curvature analysis of the column section with the inclusion of a bond/slip mechanism. Three different bond/slip models were utilized in the analysis. Further, six different FRP-confined concrete models were employed for the jacketed columns. The developed software was calibrated through a parametric study comparing the experimental and predicted results. Finally, seismic retrofit design procedure was developed for circular bridge columns with insufficient lap-splice length.