Wave action standard history (wash) for fatigue testing offshore structures: Fid-Bau Portal

Wave action standard history (wash) for fatigue testing offshore structures

Kam, J.C.P.

Abstract This paper summarises the recent development of the Wave Action Standardised History (WASH) framework as a generator of realistic service load history for fatigue testing of fixed steel offshore structural components. The development will be reported in this paper in two sections, namely, the review of monitored offshore service load histories relevant to the fatigue process, and the summary of the modelling strategy and the techniques used by the WASH framework for laboratory simulation of the standard load histories. The monitored service histories reviewed in this work were collected in the last two decades by several major offshore operators in the attempt to correlate design and realistic loading parameters. Only a small part of these data, selected on the basis of its relevance to fatigue, was examined for the WASH development. The monitored results are unique to the location, platform dimensions, configuration, payload and foundation behaviour. It is unlikely that the load history experienced by one structure will be repeated on another. Therefore, it is necessary to extract from these lengthy records the common factors relevant to fatigue. At the same time, as many characteristics of the load history as possible should be incorporated in order to avoid omitting any hidden factors related to fatigue, which may not be evident from current knowledge. The WASH model consists of a random sea-state sequence generator based on the Markov Chain technique and a random time-history generator based on the Pseudo-Random Binary Shift (PRBS) technique. The model and the implementation will be discussed in further detail.