Safety fuzzy logic model

Here the basic model used is one which is tested hi the laboratory and contains as much as is known about the influences of the X and Y parameters on the fatigue life. The known variabilities of the X and Y in the WOL are then used to calculate a fuzzy probability of failure which is the chance that the actual life will be less than the design life. A fuzzy logical hierarchy is then set up exactly as in the example of Section 10.5, to allow for the uncertainty associated with the application of the model in the laboratory. This new fuzzy probabUity is then again truth functionally modified to allow for the uncertainty of the matching with the WOL The procedure would then be exactly as for that example, so that a fuzzy truth restriction upon the statement, the structure is perfectly safe would result and this is the final measure of structural safety. 

It is very clear from the complexity of the situations described in the case studies of the last two chapters, that simple factors of safety, load factors, partial factors or even notional probabilities of failure can cover only a small part of a total description of the safety of a structure. In this chapter we will try to draw some general conclusions from the incidents described as well as others not discussed in any detail in this book. The conclusions will be based upon the general classification of types of failure presented in Section 7.2. Subjective assessments of the truth and importance of the checklist of parameter statements within that classification are analysed using a simple numerical scale and also using fuzzy set theory. This leads us on to a tentative method for the analysis of the safety of a structure yet to be built. The method,however, has several disadvantages which can be overcome by the use of a model based on fuzzy logic. At the end of the chapte(, the discussion of the various possible measures of uncertainty is completed. 

The meaning of the application of fuzzy models in risk analysis is to provide mathematical formulations that could characterize the uncertain parameters involved in complex safety evaluation me ods. Fuzzy logic is a decisional system based on linguistic rules once the membership functions have been defined for all the fuzzy variable sets, each set has to be connect by... 

Tchorzewska-Cieslak, B., 2010. Model of risk of water mains failure using fuzzy logic. Journal of Polish Safety and Reliability Association (Summer Safety Reliability Seminars), (vol. 1) 255-265. 

Returning to the structural safety problem, we can use this definition to calculate a fuzzy possibility that the calculation model is perfect. The fuzzy truth restriction upon LSM is a fuzzy truth restriction on the calculation model is perfect, given the information from the lower parts of the logical hierarchy. Thus... 

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