Fatigue assessment method of marine structures subjected to two Gaussian random loads. (1st October 2018)

• Record Type: Journal Article
• Authors: Ma, Yongliang; Han, Chaoshuai; Qu, Xianqiang
• Is Part Of: Ocean engineering. Volume 165(2018)
• Page Start: 107
• Page End: 122
• Publication Date: 2018-10-01
• Subjects: Combination of fatigue damage -- Gaussian random process -- Bimodal spectra -- Rainflow counting; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2018.07.033
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Fatigue assessment is a critical issue for marine structures which usually encounter a combination load of a low frequency and a high frequency component. Furthermore, two components are commonly analyzed separately. In a strict sense, each of two components cannot be considered as narrowband processes. Recently, the authors proposed a combination of fatigue damage method (Han-Ma method) for predicting fatigue damage on the assumption of two well-separated and narrowband Gaussian components. The method is extended to non-narrowband and frequency overlapped cases in this paper. In addition, the application of existing combined spectrum method with dual narrow-banded correction factor (such as Jiao-Moan method, Low's bimodal method, Low-2014 method) and combination of fatigue damage method (such as DNV method, Huang-Moan method) is also investigated. These methods are also compared with some general wide-band spectral methods such as Dirlik method, single-moment method, Benasciutti-Tovo method and Park method. The results show that Jiao-Moan method, Low's bimodal method, Low-2014 method and Han-Ma method can still provide very accurate fatigue damage estimation when two Gaussian processes are separately non-narrowband and have overlapped frequencies. In particular, the accuracy of Low-2014 method and Han-Ma method is very close to that from some general spectral methods in the case that two Gaussian components have overlapped frequencies. Highlights: Combination of fatigue damage formula proposed by the authors is extended to the non-narrowband and overlapped cases. This paper gives a formula for predicting the bandwidth range of the combined stress processes. The proposed method can address the situation that two Gaussian components are calculated separately. The proposed methods provide very accurate fatigue damage estimations which is close to general wideband spectral methods. Existing bimodal methods are extended to the non-narrowband and overlapped cases, they give good fatigue damage estimations.