A new approach for estimating fatigue life in offshore steel structures

Abstract

Miner’s rule is generally accepted as the fatigue criteria for life estimation of existing offshore steel structures. Similarly, it has always been acknowledged as a simplification that is easy to use in design where detailed loading history is unknown. But in the case of existing structures where the detailed loading history is known, Miner’s rule might provide incorrect results because of its omission of load sequence effect. Recently, a new damage indicator-based sequential law has been proposed to capture the load sequence effect more precisely. However, application of this sequential law to estimate the remaining fatigue life of existing steel structures has not been properly studied. The objective of this study is to estimate the remaining fatigue life of an offshore structure using the sequential law, and introduces a new approach to estimate remaining fatigue life. This approach is specially based on combination of real stress histories, sequential law and fully known Wöhler curves. The obtained fatigue life is compared and conclusions are drawn.