Characteristics of Semi-rigid Steel Frames with Fuzzy Variables

This paper presents the method for estimating the characteristics of the load-carrying capacity and displacements of semi-rigid steel frames with fuzzy variables. A nonlinear inelastic analysis method based on the refined plastic hinge method is employed to predict the load-carrying capacity and displacements of the structure since this approach yields the acceptably accurate results in much shorter analysis time compared to the plastic-zone methods. In addition, the nonlinear behaviors of semi-rigid connections are modeled by using the zero-length element and the Kishi–Chen three-parameter power model, and the generalized displacement control algorithm is applied to solve the nonlinear equilibrium equations. The α-cut method, where the lower- and upper-bounds are calculated by using the micro-genetic algorithm, is used to present the fuzzy characteristics of the structure. A semi-rigid two-story space frame example is studied. The numerical results show that the proposed method yields better results with much smaller required structural analyses compared to the Monte Carlo simulation method. In addition, the load-carrying capacity and displacements of the frame are the fuzzy variables, and the proposed method is reliable, efficient, and accurate.