Applicability of Fuzzy Logic to the Definition of the Buckling Length of Steel Plane Frames

This paper presents a fuzzy-logic-based approach to the definition of buckling length evoked by the uncertainty of joint stiffness and boundary conditions for the member support. The example demonstrates a lucid and specific application of fuzzy sets in modelling uncertainties in design. To carry out analysis, the extension principle in the form of α-cuts was used. Buckling lengths were analysed utilizing stability solution according to the second-order theory. The beam finite element method with the shape functions of sin and sinh was utilized in the analysis taking into account valuable information on the uncertainties of input data.