Accelerating time-domain fatigue screening of offshore structures with an integrated unit load response and submodelling workflow
Journal
Marine Structures
Journal Volume
109
Start Page
104104
ISSN
09518339
Date Issued
2026-07-15
Author(s)
Abstract
Time-domain fatigue analysis of floating offshore wind turbines (FOWTs) is accurate but often prohibitive in terms of computational time for early-stage design. The unit load response (ULR) method, based on linear superposition, offers an efficient alternative, but its application to large, shell-based structures with complex distributed loads remains a challenge. We propose a workflow that integrates ULRs with force-based submodelling to enable whole-structure fatigue screening at design cost. Two key innovations make it practical: (i) A "virtual test rig" is used to create a computationally fast, stiffness-equivalent simplified global model for extracting boundary loads. (ii) A ULR catalogue is generated for a detailed local submodel, which includes a trilinear interpolation scheme (with water height, pitch, roll) to efficiently handle complex, wave pressure fields. The workflow is first verified on a canonical portal frame and then applied to a full-scale semisubmersible FOWT. Across 14 critical locations, the reconstructed stress time histories match the submodel with a median bias of approximately −4%, and the stress and fatigue rankings are preserved. Compared to classic step-by-step submodelling, the method achieves ∼13–29 times lower wall-clock effort and produces outputs that are otherwise impractical at scale (e.g., full-hull damage maps), enabling earlier, more informed fatigue-driven design decisions.
Subjects
Fatigue analysis
Fatigue screening
Floating offshore wind turbine (FOWT)
Submodelling
Time-domain analysis
Unit load response (ULR)
Publisher
Elsevier Ltd
Type
journal article