Seismic Performance of Rectangular Bridge Columns with Moderate Confinement

This study is part of a project to develop detailing guidelines for reinforced concrete bridge columns and walls in areas of low to moderate seismicity. The work presented in this paper examines the ductility and behavior of rectangular reinforced concrete columns with moderate confinement. Four half-scaled rectangular bridge columns were built and tested. The transverse reinforcement ratios provided in the strong direction of the column specimens corresponded to 46 and 60 percent of the minimum lateral reinforcement required by AASHTO for seismic detailing. Each specimen was tested under constant axial load while subjected to quasi-static cyclic lateral loading in the column strong direction. The axial load indexes were 10 and 25 percent. The specimens exhibited displacement ductilities ranging between 5 and 7. Based on analytical and experimental results, an equation for designing the confinement steel for target ductility is presented.