Abstract: This paper defines the residual strength status of various kinds of structural significant items according to the characteristics of the damage occurrence and growth of these items. The random process of the occurrence of the status of various kinds and the transfer among them in the period of the structure life is analysed, and it is simulated by using the time monogeneous Markov process of discrete status and successive time. In accordance with the main contents of structure damage tolerance assessment and the statistics results of relevant data, the paper points out that the major factors to influence the occurrance of the status of various kinds and the transfer among them are fatigue, fracture, accident damage and environment corrosion, and the method of estimating the status transfer ratio matrix caused by each impact factor is proposed. From which, the formula to integrate total status transfer ratio matrix is set up. Further, the instantaneous reliability of the damage tolerance structure in its life is defined, and the approach to compute the instantaneous reliability is presented. In the last section of the paper, one calculating example is given, It can be found from the example that the structure reliability of considering maintenance program is higher than that of doing not consider maintenance program. This conclusion shows that the reliability analysis approach advanced in this paper can not only be favourable for the application and development of the damage tolerance design method, but also provide the appropriate analysis basis for the effective control of the design links and the design parameters.

Key words: damage tolerance, reliability analysis, Markov process