Full and Model Scale Testing of a New Class of US Coast Guard Cutter

The United States Coast Guard (USCG) initiated a project to assess fatigue design approaches for its new National Security Cutters (NSC). It became known as the Fatigue Life Assessment Project (FLAP). An overview of this project is provided by Stambaugh et al. (2014). Predicting the fatigue budget consumption of a ship hull structure involves the prediction of hull loading in a seaway, and comparison of this with the structural capacity. Particularly the former is an effort requiring information from a multitude of disciplines. Therefore, MARIN was contracted to support FLAP and reached out to involve other subject matter experts and stakeholders. American Bureau of Shipping, BAE Systems, Bureau Veritas, Damen Shipyards, Defense R&D Canada, DGA hydrodynamics, Lloyd’s Register, Ingalls Shipbuilding and Office of Naval Research participated in the Valid joint industry project (JIP). The broader goals of the project are to forecast structural maintenance needs of USCG Cutters, further improve the understanding of wave loading leading to fatigue damage, and increase the confidence level in predicting wave loading leading to fatigue damage on a naval frigate type hull form and structure. These goals were, among others, achieved through a model test program supported by dedicated full scale trials. Measurements taken during these trials have provided data for correlation with model experiments and numerical simulations. In order to evaluate fatigue life prediction methodologies and also forecast structural maintenance needs, a long term monitoring campaign was performed on the NSC USCGC BERTHOLF.
This paper presents the setup and the results of the dedicated trials, the monitoring campaign and the model scale tests conducted for the USCG’s fatigue life assessment project. The results presented improve the understanding of the loading side of the fatigue lifetime and forecasting fatigue damage for the NSC (WMSL) Class.