Structural System Fuzzy Reliability

Due to the stochastic and fuzzy variables in structural system reliability analysis, itis difficult to use normal model to calculate the reliability, even in some cases, the resultobtained from normal model is false. In this paper, the properties of uncertain variablesare systematically analyzed, and a series of methods are represented to calculate thefuzzy reliability of structural component and system.Firstly, investigate the computation of fuzzy FEM(finite element method) andfuzzy stochastic FEM, utilize λcut, and use interval FEM and interval algorithm, aseries of interval answers obtained, and thenλcut fuzzy reliability obtained. Whenbasic variables are fuzzy stochastic numbers, the reliability of structural component isalso fuzzy number, this consideration holds the fuzzy character in midst process, andensures the accuracy of final result.The research of structural fuzzy sensitivity shows that the fuzzy characters can notbe neglected. The research of two methods shows: (1)The direct integral method issimple, safety subjective function could be constructed in some case, but it is onlysuitable for some simple circumstance; (2)Using counterchange, fuzzy affair changedinto normal affair, get λcut of fuzzy affair and fuzzy parameters, a series intervalnumbers obtained, these interval numbers could be used in the calculation of componentreliability, and also be used in estimating the reliability of system; (3)When stress andstrength are stochastic numbers ,but their means and variances are fuzzy numbers, gettheir λcut number,　take them into first order and second moment method, intervalnumber of fuzzy reliability index obtained, use these numbers,thereliability obtained.Common expression of structural system fuzzy reliability is educed in this paper,include serial structural system, parallel structural system and serial parallel structuralsystem, and an applicable method is represented which based onβ-Unzipping method.Result shows that to insert the λcut number result obtained from structural componentreliability analysis in the calculation of system reliability not only make the result moreaccurate, but also make the best of way in normal model. Example indicates the way putforward in this paper is rational, feasible, effective and suitable for engineering, and itscomputation almost equals to normal model.