Experience and research on reinforced concrete bridges indicate that relatively stable response to strong ground motions can be obtained if the system is proportioned and detailed so that the predominant inelastic response is restricted to flexure in the column. In this case, it is important to know the strength of the column so that strengths of adjacent components can be set high enough to avoid inelastic action in those components. Details also are required that will enable the column to sustain the necessary inelastic deformations without disabling loss of resistance. Of interest are the configuration and amount of the transverse reinforcement required to sustain expected earthquake demands.
A research program is reported that examines the ductile flexural response of reinforced concrete columns of circular cross section reinforced with spiral reinforcement. The program involved laboratory tests on large-scale columns followed by analysis of the test results. The columns had a longitudinal reinforcement ratio of 2.75 percent. Transverse reinforcement varied along the height, being closely spaced near the column ends where inelastic flexure was expected and less closely spaced outside that region. Materials were normal-weight aggregate concrete, with compressive strength around 5000 psi, A706 Grade 60 longitudinal reinforcement, and A82 spiral wire. The columns were tested as cantilevers subjected to constant axial load and cyclic lateral displacements in one plane. Analyses of the data led to conclusions regarding strength, effects of varying the transverse reinforcement along the column height, and deformation capacity including models for computing the deformation capacity.
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