The Effect of Fuzzy Uncertainties on Performance Level and Performance Evaluation of Steel Moment Frames

This paper aims to ponder the effect of fuzzy uncertainties on performance evalu-ation of steel moment frame structures. Since the performance evaluation of a structure depends on its seismic demand and capacity spectra, any uncertainties in these two spectra causes uncertainty in performance level and performance point. Among many sources of uncertainties in structural dynamic analysis, in this paper, the modulus of elasticity, gravity load on the structure, dynamic properties of structure and soil properties have been considered and treated as fuzzy variables. To investigate the effect of these uncertainties, first, a nonlinear static pushover analysis program was written in MATLAB medium. Then, fuzzy inference model was used for determination of the design spectrum for different kinds of soils and seismic zones. The Effects of fuzzy uncertainties on capacity curve and capacity spectrum have been investigated on a typical example based on a new fuzzy concept in construction of the capacity spectrum of structures. Finally, performance point and performance level of structure has been determined as a fuzzy output.