05.11: Local buckling behavior of octagonal hollow cross‐section member under axial compression or bending shear

ABSTRACTAn octagonal hollow cross‐section member not only permits the use of thin plate elements, but also suppresses local buckling. The purpose of this study is to clarify how the shape of the cross‐section affects the elastic buckling strength and elastic–plastic behavior under axial compression or bending shear. For this purpose, buckling analysis using the finite element method was performed to examine the shape of a cross‐section, which was changed from a square to an octagon by chamfering the four corners of the square; the chamfer width of the member was also gradually increased. The octagonal cross‐section was compared to a square cross‐section before chamfering, and to a square cross‐section with the same width‐to‐thickness ratio. The conclusions are as follows: (1) when the shape of the cross‐section was changed from a square to an octagon, the elastic buckling strength of the member increased and its plastic deformation capacity improved. (2) Assuming that a square and an octagonal cross‐section have the same width‐to‐thickness ratio by changing the chamfer width, the elastic buckling strength of the octagonal cross‐section did not always change monotonically. (3) The plastic deformation capacity was approximately equal for both octagonal‐ and square‐shaped members when their width‐to‐thickness ratios were equal.