Fuzzy reliability analysis of concrete structures

This paper presents a methodological approach of wide generality for assessing the reliability of reinforced and prestressed concrete structures. As known, the numerical values of the parameters which define the geometrical and mechanical properties of this kind of structures, are affected by several sources of uncertainties. In a realistic approach such properties cannot be considered as deterministic quantities. In the present study all these uncertainties are modeled using a fuzzy criterion in which the model is not defined through a set of fixed values, but through bands of values, bounded between suitable minimum and maximum extremes. The reliability problem is formulated at the load level, with reference to several serviceability and ultimate limit states. For the critical interval associated to each limit state, the membership function of the safety factor is derived by solving a corresponding anti-optimization problem. The strategic planning of this solution process is governed by a genetic algorithm, which generates the sampling values of the parameters involved in the material and geometrical non-linear structural analyses. The effectiveness of the proposed approach and its capability to handle complex structural systems are shown by carrying out a reliability assessment of a prestressed concrete continuous beam and of a cable-stayed bridge.