Seismic performance and failure behavior of plastic hinge regions in flexural bridge columns

Recent developments in seismic bridge design have shifted towards a performance-based approach. The structural ductility design philosophy is still emphasized, which controls the performance of a structure by designing it with plastic hinge mechanisms that allow for ductile response. Since column plastic hinging is key in the performance of ductile bridge structures, a better understanding of plastic hinges is necessary to develop a performance-based design approach, which considers multiple performance limit states.; In this dissertation, a Bridge Performance Database using a five-level performance assessment approach was developed to catalogue the seismic response of laboratory bridge component, subassemblage, and system case studies, as well as to gain insight in the general performance of plastic hinges.; Identified performance issues with flexural concrete plastic hinges are (1) confinement, (2) shear, (3) yield penetration, and (4) bar buckling. Yield penetration and bar buckling are addressed in detail in this dissertation. An experimental test program consisting of seven, 40%-scale circular columns was conducted to investigate the effects of relocating the plastic hinge as a method to avoid yield penetration and consequent damage to connections. Results from the experimental program show that columns with relocated plastic hinges have flexural capacities within range of columns designed with plastic hinges at the end regions despite a reduction in effective column height. Furthermore, the experimental method used to relocate the plastic hinge successfully reduced yield penetration. The optimum height to relocate the plastic hinge is addressed such that only limited yield penetration exists without other behavioral problems arising. Also, improved guidelines for the equivalent plastic hinge length for relocated hinge columns is developed.; To better understand longitudinal bar buckling, which is a typical failure mechanism of plastic hinge regions, an experimental and analytical buckling study was conducted. Dimensionless assessment curves and anti-buckling design recommendations for column end hinge and relocated hinge columns are presented. Finally, an analytical 3D finite element tool that incorporates the performance assessment approach and buckling results from this dissertation was developed and validated with experimental data. With this assessment tool, an extensive parameter study can be performed to derive more reliable design equations and better understand the performance of reinforced concrete bridge columns.