Biaxial Interaction Diagrams for Short RC Columns of Any Cross Section

A general method that determines the biaxial interaction diagrams for any orientation of the neutral axis of a reinforced concrete (RC) short column of any cross section under axial load and bending about two axes is presented. Closed form expressions for MnX, MnY, and Pn are derived that evaluate the theoretical ultimate strength of RC short columns using (1) Gauss' integral method for equilibrium; (2) a nonlinear stress-strain relationship for the concrete; and (3) a multilinear elastoplastic relationship for the reinforcement. These equations and the proposed method can be reproduced by another user with minimal calculations (as opposed to other methods), allowing the designer to investigate the biaxial bending behavior and failure mode of short RC columns under compression or tension. The proposed method can also be utilized in the study of the effects of creep and confinement of the concrete on the strength and failure mode of RC short columns of any cross section under biaxial bending and axial load...

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