Bridge foundations in seismic regions are usually designed to withstand the plastic hinge moments that develop at the bases of the columns. Various hinge details have been proposed to reduce or even eliminate the moments transferred to the foundations, and thereby reduce the sizes and costs of the foundations.
This study experimentally investigated the behavior of column specimens incorporating different moment-reducing hinge details. Tests were performed on reinforced concrete column specimens subjected to increasing inelastic lateral displacements under constant axial load. The study investigated effects on hinge performance of several parameters, including vertical discontinuity in the hinge detail, level of axial load, low-cycle fatigue characteristics, column aspect ratio, and different amounts of longitudinal and transverse reinforcement.
The test results of this investigation showed that hinge details can be incorporated into columns to significantly reduce the moment capacity at the bases of the columns. However, the moments are not negligible, as is sometimes assumed for design with the moment- reducing hinge details. Providing vertical discontinuity in the hinge resulted in reduced distress in the longitudinal reinforcement and improved the performance of the hinge. Preliminary design recommendations were proposed for the comprehensive design of moment-reducing hinge details at the bases of the bridge columns.