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 plastic moments transferred to the foundations, and thereby, reduce the sizes and costs of the foundations. However, no code specifications for these moment-reducing hinge details currently exist. The behavior of column specimens incorporating different moment-reducing hinge details was investigated. Tests were performed on reinforced-concrete column specimens subjected to increasing levels of cycled inelastic displacements under constant axial load. The effects on hinge performance of several parameters were investigated, including providing 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. Using the test results, hinge details can be incorporated into columns to significantly reduce the moment capacity at the bases of the columns. The moments are not negligible, as is sometimes assumed for design with the moment-reducing hinge details. Providing verticaldiscontinuity in the moment-reducing hinge details results in reduced distress in the longitudinal reinforcement and improved performance of the hinge. Preliminary design recommendations are proposed forthe comprehensive design of moment-reducing hinge details at the bases of bridge columns. This paper appears in transportation researchrecord no. 1319, Bridge and hydrology research 1991.
Samenvatting