A square hollow section member is generally used as a column in steel structures. Local buckling is known to affect the large deformation behavior. Local buckling is more likely to occur when the width-thickness ratio of the plate elements is large. Therefore, an octagonal cross sectional member that can reduce the width-thickness ratio of the plate elements and reduce the material is expected to be column.
Although there have been many previous studies on octagonal cross sectional members, none have examined the inelastic behavior of octagonal cross sectional members subjected to shear bending. In this study, the plastic deformation capacity of an octagonal cross sectional member subjected to shear bending is clarified based on the actual behavior of the member, and an evaluation method is proposed.
In this study, the buckling coefficient of an octagonal cross sectional member under compression or bending is calculated by eigenvalue analysis using the finite element method, and a buckling coefficient evaluation formula for octagonal cross sectional members under compression or bending is proposed.
In addition, the plastic deformation capacity of the octagonal cross sectional members was confirmed by the large deformation analysis of the cantilevered column form under axial and bending shear forces for the octagonal cross sectional members. In the comparison, the effect of the length of both members on the large deformation behavior was studied, and the plastic deformation capacity was investigated using a square hollow section member with the same thickness-width ratio of the plates. Next, in order to investigate the effect of the maximum value of initial imperfections on the plastic deformation capacity, a large deformation analysis is performed using the maximum value of initial imperfections as a parameter.
In order to understand the actual behavior of the octagonal cross section members, the plastic deformation capacity of the octagonal cross section members was confirmed by cantilevered bending shear tests and compared with the plastic deformation capacity of the square cross section members with equal width and length.
The buckling coefficient evaluation formula for octagonal cross section members obtained in this study is applied to the new width-thickness ratio for square cross-section members proposed in Reference 2), and the plastic deformation capacity evaluation formula using the new width-thickness ratio for square cross section members proposed in this study is examined whether it is possible to evaluate the plastic deformation performance of octagonal cross section members obtained by large deformation analysis and loading tests. The effect of the initial imperfection on the plastic deformation capacity of the square and octagonal cross section members is taken into account.
