Utilizing an Acceleration-Strain Transmissibility Relationship for the Prediction of Midship Strain on a Polar Vessel

Abstract In shipping, the evolution of cyber-physical connectivity enables benefits to inform decision making toward increased vessel safety, enhanced passenger comfort, and sustainable operations. A polar supply and research vessel suffers from accelerated fatigue as a result of wave slamming, which leads to resonant excitation of the structure. A full-scale monitoring system is installed on the vessel, which consists of a network of 26 acceleration sensors mounted at various locations on the structure. In a recent update of the measurement system, two strain sensors were added near the midship point, where the cross-section profile of the vessel changes significantly. Due to limited sensor locations, estimating stress hotspots or the stress distribution along the length of the hull proves challenging. The present work attempts to gain insight into the validity of utilizing vibration transmissibility functions to predict structural strain at a specific measured location from operational acceleration data. Operational Transfer Path Analysis is performed with acceleration and strain data measured during a voyage between South Africa and Antarctica. In the frequency domain, a transmissibility-based transfer function model is synthesized that relates the vibration path contributions to an estimated strain near midship. This predicted strain is validated with measured operational data at the same location for various ocean conditions. This work is the first step towards enabling virtual strain measurement on a vessel prone to impulsive slamming loads. This innovation enables the progression of the digital twin concept into a decision-making tool that provides insight into accumulated fatigue from normal operations and the high-frequency component associated with slamming.