Moment-Curvature Characteristics of Reinforced Concrete Members Subjected to Axial Load and Reversal of Bending


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Title: Moment-Curvature Characteristics of Reinforced Concrete Members Subjected to Axial Load and Reversal of Bending

Author(s): Hiroyuki Aoyama

Publication: Special Publication

Volume: 12


Appears on pages(s): 183-212


Date: 1/1/1965

With discussion by Kurt H. Gerstle and Leonard G. Tulin, and Hiroyuki Aoyama. The objective of this investigation was to establish moment-curvature relationships of reinforced concrete members subjected to constant axial load and reversal of bending. Both the theoretical and experimental approaches have been made, guided by the results of previous experimental investigations. A method of analysis was developed, based on three assumptions: a linear strain distribution over the section; elasto-plastic stress-strain relationship of steel neglecting the Bauschinger effect; elasto-plastic stress-strain relationship of concrete replacing the real curve and neglecting any stress in tension. The effects of variables were studied using this analysis. Reinforcement ratio and concrete strength had minor effects on the shape of momentcurvature diagram. The amount of axial load and the plastic deformation under the previous loading made drastic change. When the member had no axial load, the diagram had a shape like a parallelogram and larger the plastic deformation, the wider the diagram was in the horizontal direction. When the amount of axial load was small, the moment-curvature diagram had a step in the way of reversal, and the larger plastic deformation made this step larger. When the axial load was higher, this step became smaller and for even higher axial load it vanished completely, making a spindleshaped diagram. Tests were made on three reinforced concrete specimens, making all the measurements in the constant moment region of the specimen. The validity and limitation of theoretical analysis were checked. It was found that the agreement was almost perfect for initial loading and for the first reversal made slightly after the yielding in the initial loading. However, the agreement was not very good for reversals after the first reversal from a point considerably beyond the yielding. Study of this discrepancy indicated some modifications of the method of analysis.