Abstract
This paper describes the experimental and analytical results carried out to investigate the influence of changing axial force on the restoring force chracteristics of reinforced concrete columns. 11 specimens are tested under two-point loading and subjected to pure bending moment and axial force in the test length. 5 of them are tested under loading condition of constant axial force and increasing lateral load. 6 of them are tested under loading condition that axial force and lateral load are changing by turns or at the same time. The relationships between moment and curvature in the test length are analyzed based on the properties of materials and on the assumption that the plane section remains plane after deformation. The results of the experiments and analysis are as follows; (1) The yield moment is not influenced by load paths, and depends on magnitude of axial force when tensile reinforcement yields. (2) When axial force increases under constant lateral load, curvature decreases a little. And when lateral load increases under the constant axial force, the relationship between moment and curvature draws towards that of the specimen tested under loading condition of the constant axial force and increasing lateral loal. (3) When axial force decreases under constant lateral load, curvature increases and comes up to the curvature of the specimen tested under the constant axial force. (4) The analysis agrees with the experimental results except some differences. It is considered that these differences come from taking no account of the bond between concrete and reinforcement in the analysis.
