Analytical investigation of the stiffness of non-sway eccentrically loaded slender reinforced concrete columns

Ryan William Jenkins, Purdue University


The modern slender concrete column provisions were introduced into the Building Code Requirements for Reinforced Concrete in 1971. Though the methodology is considered sound, the expression for estimating the effective stiffness, EI, remains a concern. The very conservative and simple expressions for the estimation of the effective stiffness introduced in 1971 continue to be included in the current building code. While recent research has resulted in the addition of another expression for estimating the effective stiffness, this expression is relatively complex and is typically not used in design. The objective of this research study is to investigate the development of simplified design equations that reliably estimate the stiffness of slender concrete columns subject to non-sway, second-order effects. Using simple material stress-strain interactions and basic mechanics, an analytical model was developed and evaluated against previous experimental tests of eccentrically loaded reinforced concrete columns. Next, a parametric study investigated the effects of column variables on the effective stiffness of the column. Finally, expressions appropriate for design were developed and compared with the current design procedures. Based on this review, an improved design equation to estimate the stiffness of slender columns is recommended.




Frosch, Purdue University.

Subject Area

Civil engineering

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