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Title: Slenderness Lower Limit for Sway-Inhibited Reinforced High-Strength Concrete Beam-Columns

Author(s): Monther B. Dwaikat and Mahmud M. S. Dwaikat

Publication: Structural Journal

Volume: 115

Issue: 5

Appears on pages(s): 1243-1252

Keywords: axial-moment interaction; beam-column; design guidelines; finite element modeling; high-strength concrete; second-order effect; slenderness ratio

DOI: 10.14359/51702228

Date: 9/1/2018

Abstract:
In the design of reinforced concrete (RC) beam-columns, provisions in some buildings codes and standards stipulate that if the slenderness of such members is less than a certain lower limit, the second order effect can be neglected and the member is designed based on its cross-sectional capacity. Even though such lower limits were originally based on columns made of normal-strength concrete (NSC), the lower limits are presented in these codes and standards even for columns made of higher-strength concretes (HSCs). The current study investigates the applicability of such lower limits for HSC. A nonlinear finite element model of RC columns is developed using ANSYS and validated against published test data, and is then used to construct interaction axial-moment (P-M) diagrams for slender RC columns considering both material and geometric nonlinearities. The lower slenderness limit for sway-inhibited columns is reestablished based on the finite element results and compared to the limits provided in codes and standards. Also, the elastic solution is used with essential modifications to study the trend of behavior and its results are also compared to the finite element results. The study found that the limits given in the ACI Code and Eurocode are generally conservative for NSC columns but not for HSC, especially for the case of equal end moments with single curvature. Using the finite element results, a new limit for the lower slenderness for HSC columns is proposed.