It has been noted that the use of safety coefficient can deal with uncertainties existed in practical structures, while reliability concept provides more precise results by considering the real distribution of creep rupture property. Generally, creep rupture data of a heat-resistant steel can be compressed into a narrow band by using a temperature-time parametric method such as Larson-Miller or Manson-Haferd method. In order to describe the scattering of the data, the current paper proposes a “Z parameter” method to represent the magnitude of the deviation of the rupture data to master curve. Statistical analysis shows that the scattering of Z parameter for several types of steels is supported by normal distribution. Using this method, it is possible to achieve unified analysis of the creep rupture data in various temperature and stress conditions. Stress-TTP-Reliability curves (σ-TTP-R curves), Stress-Rupture time-Reliability curves (σ-tr-R curves) and Allowable stress-Temperature-Reliability curves ([σ]-T-R curves) are proposed which could embrace reliability concept into creep rupture property design.

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