Session: 02-05-01 Data-driven and AI-based Models

Submission Number: 182036

A Case Study of Long-Term Wave Bending Fatigue Using Directional, Zone-Specific Wave Spectra 

The operations of the SA Agulhas II polar Supply and Research Vessel are considered from 2012 to 2021 in a long-term structural analysis. Directional, zone-specific wave scatter diagrams were generated using open source ERA5 reanalysis data (0.5 degree spatial resolution, 3 hour temporal resolution). This reanalysis data is used to inform operations of SA Agulhas II which extend further south than the defined nautical zones of the Southern Ocean. The scatter diagrams serve as input to a long-term spectral fatigue analysis. It assumed that the ship was loaded to a draft of 7.7 m in an Antarctic departure condition, which is deemed representative of the majority of her open water operations. The bending RAOs of the ship are calculated using HydroStar software. The low-frequency wave bending fatigue at hull frame #98 was estimated owing to recurring fatigue cracks in this location. Long-term fatigue damage accumulation results are presented with respect to the recurring routes. The validity of these results is reflected on through a concurrent measurement of longitudinal strain at hull frame #98, combined with spectral fatigue estimates for a dedicated test sequence. The results indicate that the damage rate per hour is the highest on the annual voyage between the Antarctic Ice Shelf and South Georgia Island. Additionally, spectral fatigue estimates and fatigue damage determined from strain measurements correlate well for head- and stern-wave conditions, but suffer a discrepancy in stationary conditions in stern- and bow-quartering seas.

Presenting Author: Anriette Bekker Stellenbosch University

Presenting Author Biography: Anriëtte(Annie) Bekker discovered her passion for the vibration of structures as a third-year student in Mechanical Engineering at Stellenbosch University. This field has led her career to diverse research topics including dynamic seat comfort of cars for Ford Motor Company and the prediction of bone fracture of vehicle occupants during landmine blast events for the Armaments Corporation of South Africa. In industry, she worked as the technical lead on noise, vibration and harshness for Optimal Energy Pty. Ltd. She joined the Faculty of Engineering at Stellenbosch University in July 2011 where she has been a professor since 2020. She is a keen test engineer and has led multi-sensor measurement campaigns on the heavy mobile equipment fleet for Richards Bay Minerals and polar ships including the South African SA Agulhas II and the German Polarstern. Presently, her work aims to reap novelty from the use of operational data for decision aiding. She is registered as a professional engineer with the Engineering Council of South Africa and serves on the editorial team of the Elsevier Journal Cold Regions Science and Technology. She holds the Gibela Engineering Research Chair to drive research into South Africa’s new passenger trains. In 2025 she was awarded a second Chair position as the DSTF/SAIMI Chair in Naval Architecture and Design.

Authors:

Anriette Bekker Stellenbosch University
Karl-Heinz Pferdekamper Stellenbosch Univeristy