A reliability-based approach can play an important role in avoiding excessive conservative design for piping. We showed a formulation for applying the limit state function method to reliability-based fatigue design at the previous PVP conference. Using this method, the reliability can be expressed by two dominant parameters: the distribution of equivalent stress and the distribution of fatigue life. If the equivalent stress under stationary random loading can be related to some specific spectrum parameters, it is expected that reliability-based fatigue design can be achieved under random loading. Fatigue damage under random loading is usually estimated using Miner’s law together with the SN diagram. In applying Miner’s law, the random wave is decomposed to the fatigue range using some counting method. The rainflow cycle counting (RFC) method is widely used as a counting method. In view of design application, however, the estimation of fatigue damage from spectrum characteristics is important, and the RFC method is not necessarily suitable for this purpose because it is rather difficult to use in the analytical treatment. Fortunately, it has been shown that the level crossing counting (LCC) method provides a more conservative estimation when compared with the RFC method and the analytical treatment for the evaluation is available. In this paper, we will show a procedure for reliability-based fatigue design which evaluates fatigue damage using the LCC method, spectrum characteristics and Miner’s law.

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