Bridge foundations in seismic regions are designed to withstand the plastic hinge moments that develop at the bases of the bridge columns. In columns that are oversized for architectural or other reasons, this approach results in excessively large foundations. Varioushinge details have been proposed to reduce the plastic moments transferred to the foundation and thereby reduce the size and cost of the foundation. The results of an experimental investigation of the seismic performance of bridge columns with moment-reducing details arepresented. Tests were conducted on reinforced concrete column specimens subjected to axial load and cycled inelastic lateral displacements. The main parameters investigated in the testing program were different moment-reducing hinge details, the column aspect ratio, the level of axial load, and low-cycle fatigue characteristics. Columns with the moment-reducing details exhibited stable hinging behavior, even when subjected to repeated cycles at large displacement levels.The hinging behavior was similar to that for a conventional column with the same hinge dimensions and reinforcement. Flexure dominated the behavior of all the columns in this study, including those with an aspect ratio of 1.25. The level of axial load had only a limited effect on the behavior of the columns, with the moment-reducing details due to the confinement provided around the hinge region by the outer architectural column. This paper appears in transportation research record no. 12 Research 1990.
Abstract