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Title |
Effective Flexural Stiffness for Analysis and Design of Reinforced Concrete Columns
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Authors |
박요셉(Yo-Seb Park) ; 엄태성(Tae-Sung Eom) |
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DOI |
https://doi.org/10.4334/JKCI.2026.38.4.443 |
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Keywords |
기둥; 유효강성; 모멘트확대계수; 2차효과; 안정성설계 column; effective stiffness; moment magnification factor; second-order effects; stability design |
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Abstract |
The current design code (KDS 14 20 20) provides simplified models for the effective stiffness of reinforced concrete columns; however, these models often result in overly conservative estimates when applied to the moment-magnification method. In contrast, ACI 318-25 promotes a more rational approach to column design by adopting an alternative effective stiffness model. This study investigates the suitability of various effective stiffness models for columns specified in current design codes, in terms of strength design and structural analysis. The theoretical foundations and characteristics of these effective stiffness models were compared, and their accuracy in capturing the increases in column deformations and moments due to second-order effects was assessed. The alternative models provided reasonable predictions of column deformations and moments under serviceability conditions, but significantly underestimated them near the ultimate limit state, specifically, in the high-load region approaching the PM interaction diagram. Nevertheless, they produced accurate estimates as long as the second-order moment increase remained below 40 % of the first-order moment. Based on these findings, recommendations for column effective stiffness are proposed.
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