The goal of the research described in this report was to generate experimental data with which to study bar buckling in reinforced concrete columns. Eight circular columns, reinforced with longitudinal bars and circumferential spirals, were constructed and tested under constant axial load and cyclic lateral displacements. In the first four specimens, different displacement histories were used, including two highly asymmetric histories. In the second four specimens, the strength and stiffness of the spiral were the study parameters, which were varied independently. The columns were heavily instrumented, and special measures were adopted to detect the onset of bar buckling. This proved necessary because buckling was detected by the instruments before it became visible to the human eye.
Bar buckling always occurred during a half cycle of drift in which the strain increment was compressive, following a half cycle of substantial tensile strain increment. However, the absolute strain at buckling was in many cases tensile. It was also found that within the range of values studied, the stiffness and strength of the spiral had a statistically insignificant effect on the drift, or drift increment, at the onset of buckling.
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