A procedure to generate design load-time histories for fatigue strength assessment of offshore structures. (1st October 2020)

• Record Type: Journal Article
• Authors: Li, Shanshan; Dong, Yan; Guedes Soares, C.
• Is Part Of: Ocean engineering. Volume 213(2020)
• Publication Date: 2020-10-01
• Subjects: Storm model -- Variable storm duration -- Seasonal wave data -- Fatigue crack propagation -- Offshore structures; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2020.107707
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: This paper presents general procedures to generate loading histories for fatigue strength assessment of offshore structures based on a storm model and seasonal wave data. Using hindcast wave data of 11 years at one point in the North Atlantic Ocean, the relations among the storm duration, storm crest and the number of levels in a storm are formulated and the statistics of storm duration are obtained. One year, including four seasons is chosen as the reference period of the loading history. Based on the generated loading histories, fatigue crack propagation analyses are performed on a tubular T-joint using a fatigue crack growth model considering the load interaction and R -ratio effect. The crack size uncertainty caused by randomly generated loading histories is investigated. The proposed procedures can lead to a good agreement with the observed significant wave height distribution. The generated loading histories result in median crack growth curves, comparing with those from measured wave data. The crack size is subjected to considerable uncertainty after a period of crack propagation. Ignoring the load interaction effect leads to faster crack growth, which may be the most convenient way to achieve a conservative fatigue crack propagation analysis using only one generated load history. Highlights: A general procedure to generate fatigue load-time histories in the design of offshore structures is presented. The procedure is based on the storm modelling with variable storm duration. The load condition that leads to the largest fatigue damage in the structure, is found to be the design loading. The fatigue life under the generated design load-time history is compared with that under the source hindcast data.