A robust method for load-carrying capacity assessment of semirigid steel frames considering fuzzy parameters

Abstract

The non-probabilistic approach based on fuzzy logic has been applied in analyzing and assessing steel structures. However, there is still a dearth of studies on the behavior of nonlinear inelastic semirigid frame structures in the presence of fuzzy uncertainty. Moreover, accurate fuzzy analysis of structures often involves high computation cost. In this paper, a robust method for the prediction of the load-carrying capacity of semirigid steel frame structures defined with fuzzy parameters is proposed. For the analysis purpose, the nonlinear inelastic analysis taking account of both material and geometrical nonlinearities is adopted to estimate the ultimate load factor (ULF11ULF is the ultimate load factor of the semi-rigid steel frame structure.) of the structure. Columns and beams are modeled by the beam–column element with a refined plastic hinge at two ends, and the beam-to-column connections are defined by zero-length semirigid joints. Innovatively, a fuzzy estimation procedure named the Moving Extrema Method (MEM) is developed to efficiently capture the variation of ULF due to fuzziness in the structural properties and applied loads. Applications to three semirigid steel frames having a relatively large number of fuzzy parameters are conducted. Numerical results show that the proposed MEM can predict the fuzzy ULF with relatively high accuracy and reasonable computation volume. More insights on the effect of the fuzzy structural parameters on the ULF are also presented.