The collapse of steel model columns with unequal flanges. II. Imperfect

The collapse behaviour of pin-ended steel columns with unequal flanges is investigated using a modified version of the Shanley model. Particular attention is given to the effect of the geometrical imperfection size on the behaviour of columns having a range of flange area ratios and slenderness values. Columns which are initially straight are dealt with in a companion paper (The collapse of steel model columns with unequal flanges. I. Perfect. International Journal of Mechanical Sciences, in press, doi:10.1016/j.ijmecsci.2004.09.005). Compressive yield of the smaller flange is confirmed as an important source of failure for the column. However, tensile yield of this flange can also cause failure, particularly at relatively high slenderness and/or imperfection size. Failure caused by yielding of the smaller flange, whether compressive or tensile, is often characterised by violent load-shedding, and high imperfection-sensitivity, and this is most noticeable at intermediate slenderness. A graphical method is suggested for predicting the maximum load, and for showing the degree of imperfection sensitivity.