Integrity of glass-reinforced plastic (GRP) vessels under ice loading

Abstract

Small glass-reinforced plastic (GRP) vessels, such as lifeboats and fishing vessels are occasionally used in sea ice conditions, despite the lack of structural design standards and operating standards for such conditions. In addition, there is limited knowledge relating to the magnitude of local ice loads on these vessels or the structural integrity of these craft under ice loading. To address these gaps, full-scale measurements relating to lifeboat-ice interactions were collected during a field campaign carried out in 2013 and 2014. During these trials, the local ice loads on the hull of a Totally Enclosed Motor Propelled Survival Craft (TEMPSC) operating in pack ice conditions were measured using instrumented load panels. This full-scale field data provides the foundation for risk-based design load estimation and has been analyzed using the event-maximum method of local ice pressure analysis. This approach is based on probabilistic methods developed for the analysis of ice loads measured on icebreakers, which have been adapted for ice interaction scenarios involving small vessels. Results from this work provide improved understanding into the nature of loads on small GRP vessels operating in ice-covered waters and help to inform design methodology for these vessels. To compliment these results, the field trials were also assessed in terms of the operational methods used by different coxswains when maneuvering through an ice field. Insights from this analysis provide operational guidance towards methods that can mitigate peak impacts and improve the maneuverability of these vessels in ice.