Open Access

ARTICLE

Fatigue Assessment of Large-Diameter Stiffened Tubular Welded Joints Using Effective Notch Strain and Structural Strain Approach

Dan Jiao^1,2, Yan Dong^1,2,*, Hao Xie³, Yordan Garbatov^4,*, Jiancheng Liu⁵, Hui Zhang⁵

1 Yantai Research Institute of Harbin Engineering University, Harbin Engineering University, Yantai, 261400, China
2 College of Shipbuilding·Engineering, Harbin Engineering University, Harbin, 150001, China
3 Marine Design and Research Institute of China (MARIC), Shanghai, 200000, China
4 Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade de Lisboa, Lisbon, 1649-004, Portugal
5 China Merchants Marine and Offshore Research Institute Co., Ltd., Shenzhen, 518000, China

* Corresponding Authors: Yan Dong. Email: ; Yordan Garbatov. Email:

(This article belongs to the Special Issue: Advances in Fatigue Life Prediction and Reliability Assessment)

Computer Modeling in Engineering & Sciences 2025, 145(3), 3197-3216. https://doi.org/10.32604/cmes.2025.074239

Received 06 October 2025; Accepted 27 November 2025; Issue published 23 December 2025

Abstract

Floating offshore wind turbine platforms typically use stiffened tubular joints at the connections between columns and braces. These joints are prone to fatigue due to complex weld geometries and the additional stress concentrations caused by the stiffeners. Existing hot-spot stress approaches may be inadequate for analysing these joints because they do not simultaneously address weld-toe and weld-root failures. To address these limitations, this study evaluates the fatigue strength of stiffened tubular joints using the effective notch strain approach and the structural strain approach. Both methods account for fatigue at the weld toe and weld root and can be applied to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) regimes. Reanalyzes of a series of fatigue-tested specimens confirm the effectiveness of both approaches. The stiffener-shell fillet weld root is identified as the most critical fatigue location, which is consistent with fractographic observations. Although the brace-to-shell weld root exhibits lower stress levels in finite element (FE) models, weld quality was determined to be a crucial factor in fatigue failure. Furthermore, the results emphasise the importance of material plasticity in the LCF regime and demonstrate that full weld penetration significantly enhances fatigue strength. These findings provide valuable insights for the fatigue design of stiffened tubular joints in floating offshore wind turbine platforms.

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Keywords

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