Serviceability behaviour of PC structures by probabilistic and fuzzy probabilistic approaches

The evaluation of the safety level in concrete structures should be carried out considering the stochastic behaviour of the main parameters involved, not only under ultimate conditions, but also under serviceability and durability conditions. Particularly in concrete structures, the large variability of mechanical and rheological parameters may give rise to important deviations from the expected behaviour if a deterministic approach is used. On the other hand, it is well known that the probability density function and its parameters cannot be univocally defined. To overcome this problem, the fuzzy probabilistic theory may be used in the processing of stochastic parameters, taking into account their fuzzy nature. In this paper, a probabilistic analysis and a fuzzy probabilistic analysis of a bridge prestressed beam is performed in order to evaluate its behaviour under serviceability conditions, with particular attention to the crack formation limit state. Shrinkage, creep and tensile strength are considered to be stochastic variables, whilst for the other variables involved (e.g. live loads, etc.) are considered to be deterministic values. The comparison between the two approaches put demonstrates the peculiarity of the fuzzy probabilistic procedure that reproduces a more comprehensive safety estimate method.