Stability of Slender Reinforced Concrete Columns Subjected to Biaxially Eccentric Loads

The elastic-plastic behavior of pin-ended reinforced concrete slender columns subjected to bi-axially eccentric loads is investigated experimentally and theoretically. The ultimate loads, longi-tudinal and transverse deformations and the behavior up to failure of the columns are examined in detail. A total of 36 column specimens with rectangular cross sections including square sections were tested. The ratios of column length to minimum depth ranged from 6 to 26. Loads were applied monotonically at each column end with equal eccentricities at various angles from an axis of sym-metry. The ultimate load carrying capacity of a slender column is reduced by additional eccentri-city due to lateral deflection even in a column having a length to depth ratio of 15. The numeri-cal analysis to solve the load-deformation response of the column predicts the test behavior very well. In the case of square columns, there is not much difference in the ultimate loads of the col-umns in spite of variation of the angle of eccentricity of the applied load. However, the remark-able effects of biaxial bending on the elastic-plastic behavior occurs with the rectangular columns. When the rectangular columns are subjected to biaxially eccentric load to cause bending about the near-strong axis, the ultimate loads and the deformation behavior are significantly affected by the bending about the weak axis of the section. 1