抄録
Cold-formed steel members are widely applied in low-rise residential houses. One of the key issues in their design is the local buckling strength under compression. It is well known that the local buckling strength of a plate element is affected by its boundary condition and the section shape significantly affects its maximum strength. Moreover, the design provisions usually assume that the plate elements, which comprise a cold-formed steel members section, behave like a simply supported plate and do not consider the restraining effect between adjacent plate elements. In this paper, we focused on the restraining effect between adjacent plate elements and investigated their elastic and inelastic local buckling strength by finite strip analysis and finite element analysis.
First, we investigated the elastic local buckling strength and maximum strength of rectangular sections by numerical analysis; finite strip analysis and finite elements analysis. Through these numerical analysis, we found that the local buckling strength of long side plate element, which comprise the rectangular section, shows higher strength than that of simply supported plate elements under axial compression. This strength increase is caused by the restraining effect between adjacent plate elements; the rotation at longitudinal edges of long side plate was restrained by short side plate elements.
Then, based on the energy method, a semi-theoretical equation for the elastic local buckling strength on a restrained plate element was derived, which assume that the deflection of a restrained plate element whose longitudinal edges are elastically restrained can approximate the linear sum of the displacement function of simply supported plate element and that of the fixed plate element. The suggested equation agreed well with the elastic local buckling strength of rectangular sections obtained by eigenvalue analysis.
Finally, we evaluated the maximum strength and inelastic buckling strength of rectangular section members and lipped C section members by the developed equation; which can evaluate the elastic local buckling strength of restrained plate elements. Through the comparison between the nominal strength which consider the restraining effect and that ignore the restraining, it was found that the variation of nominal strength with respect to the maximum strength could be decrease considering the restraining effect between adjacent plate elements.
