Sparsely Connected Built‐Up Columns

Abstract

An elastic analysis is presented for the initial buckling and the postbuckling Behavior of simply supported built‐up columns consisting of two slightly separated identical parallel elements that are joined together at their ends and middle by rigid connections of negligible axial extent. Numerical results for initial buckling indicate that a familiar design rule (to make the slenderness ratio of the individual elements between fillers riogreater than that of the column as a whole) will not necessarily lead to a buckling strength approximating that of the integral column. The post‐buckling numerical results, in the form of loadshortening curves, show that the post‐buckling behavior is unstable, i.e., the load required to maintain, any buckled configuration is less than that required to initiate the buckling. This post‐buckling instability, which is in marked contrast to the virtually neutral stability of the solid elastic column, has important implications regarding imperfection sensitivity. Embedded in the general analysis is that of the 2‐connection column obtained by omitting the middle connection.