On the probabilistic failure assessment diagram

Reliability analysis of structures containing defects carried out directly by practising engineers is quite complex and costly. Therefore, a simple an d convenient reliability analysis method should be investigated and establi shed. in this paper, the principle and building procedure of a reliability analysis method are described and the feasibility of the method are also ex plicitly clarified. Based on the assumptions that: (1) the load is a determ inistic variable; (2) the yield strength and fracture toughness satisfy nor mal distribution and their variational coefficients are constant; (3) the i nitial crack length remains unchangeable, a set of probabilistic failure as sessment diagrams (PFAD) called elementary reliability assessment method ar e established under the simplified option 1 curve of the 3rd version of CEG B R6. The investigation shows that the distribution of random safety factor and failure probability of a structure only depend on the coordinates of t he expectation of P(L-r, K-r) in the failure assessment diagram of the simp lified option 1 curve and is not influenced by the other factors. The inves tigation further shows that the failure probability will decrease with the increase of the initial crack length if the expectation of P(L-r, K-r) keep s unchanged. A conservative result will be,given when using the PFAD as an elementary reliability analysis method to assess the integrity of a structu re and only a simple procedure is required like the deterministic assessmen t method given in CEGB R6. When the secondary stress exists, the conservati veness of the result assessed will increase with the increase of parameter rho although the PFAD is only established based on considering primary stre ss. (C) 1999 Elsevier Science Ltd. All rights reserved.