Creep Buckling of Imperfect Columns

Problems in creep buckling of columns have generally been analyzed based on the assumption of small deflection. However, it is known that the critical time for creep buckling is determined by unbounded deflection or deflection rate. Thus a more rational consideration of creep buckling problems would necessarily include large deformation. In this paper, a study of the creep buckling of two simple columns with geometrical imperfections associated with finite deformations has been made. The material property of the column is considered to satisfy a power law for creep deformation and a generalized Ramberg-Osgood relation for noncreep deformation. It is found that creep buckling at a finite time would exist only when the magnitude of the load is between two bounds. If the load is greater than the upper bound, instantaneous buckling would occur. On the other hand, if the load is smaller than the lower bound, creep buckling would not occur at any finite time. Misleading conclusions on creep buckling caused by the small deflection assumption are also investigated.