The strengths of PFRP thin-walled columns are determined according to the modes of
buckling which consist of local mode for short columns, global mode for long columns, and
interaction mode between local and global modes for intermediate columns. Unlike the local and
global buckling, the buckling strength of interaction mode is not theoretically predictable. Refined
theoretical approaches which can account for different elastic properties of each plate component
consisting of a PFRP thin-walled member are used. Based on both the analytical buckling loads and
the experimentally measured buckling loads from literatures, the accuracies of Ylinen’s equation and
modified AISC/LRFD column design equation for isotropic steel columns were compared. From the
comparison, it was found that the modified AISC/LRFD column design equation is more suitable for
the prediction of the buckling loads of PFRP thin-walled members than Ylinen’s equations.