Numerical Nonlinear Buckling Analysis of Tapered Slender Reinforced Concrete Columns

摘要

Tapered columns could be used either for architectural purposes or for structural needs to accommodate the variation of moments along the height of the column. In highway bridges, tapered columns are usually used to reduce the amount of moments that are transferred from the column base to the foundation. This paper studies slender RC columns with a linear variation in the columns' cross section in both the principal directions of the cross section. Two slenderness ratios of 70 and 40 have been investigated in this study for RC tapered columns. Computational analysis, using the finite element (FE) method, is conducted in this study after the calibration of the reference FE models with tests that were conducted by other researches in Jenkins (Improving the design of slender, concrete columns. Doctoral dissertation, Purdue University, West Lafayette, 2015). These FE models were extended to account for different degrees of column tapering. The paper found that a minor tapering of the column (where the tapering ratio is greater than 150) is just an esthetic feature and it does not contribute to the buckling load of RC columns. In case of slender columns with a slenderness ratio of 40, the increase in the tapering of the column causes a slight increase in the buckling load of roughly 15%, as compared with non-tapered columns that have the same slenderness ratio. On the other hand, the increase in the buckling load of columns that have a slenderness ratio of 70 is about 45%. Analytical solutions based on the eigenvalue problem have also been presented to estimate the buckling load of a variety of tapering ratios.