Ductility of Thin-Walled Steel Box Stub-Columns

Abstract

Thin-walled steel box columns are vulnerable to damage caused by local and overall interaction buckling during a major earthquake. To provide enough information for a reliable and simple ductility evaluation procedure for such structures, the attention of this study is focused on the ductility capacity of thin-walled steel box stub-columns with or without longitudinal stiffeners. Combined compression and bending loads are applied to the stub-columns to simulate the loading condition under horizontal earthquake actions. Extensive parametric analyses are carried out to investigate the relation of the stub-column ductility to various parameters such as the flange width-thickness ratio, axial force, stiffener's slenderness ratio, cross-sectional shape, and column aspect ratio. An elastoplastic large deformation FEM analysis is employed and both residual stresses and initial deflections are taken into consideration. Consequently, empirical ductility formulas are proposed. Applications of the formulas to practical structures are presented in a companion paper.