Prediction of Extreme Ammunition Cargo Forces at Sea.

Abstract : In this study, four ships, representative of ammunition cargo ships entering and leaving U.S. ports with ammunition cargo capacities ranging from about 6,300 to 19,200 tons, were examined. Ship motions and accelerations were developed in the frequency domain for a wide range of ship load conditions, headings, speeds, and sea conditions. The influences of storm severity and ship operator strategies in storms on the magnitude of the resulting ship responses and cargo shoring loads were examined using a math model of the ship traversing the North Atlantic Ocean. A cargo shoring model was developed to establish both lateral and normal forces that shoring must withstand to prevent shifting of ammunition cargo. The model consists of a time simulation developed in the coordinate system of the ship. Results suggest that cargo shoring loads based on frequency domain ship response predictions will be much greater than results based on the more accurate time domain simulations. It was concluded that, in order to prevent predictions of unrealistically large design shoring loads, shoring loads should be developed directly in the time domain. It is crucial to explore the cargo shoring model application further, e.g., to other ships, in any efforts to develop a simple shoring load rule which may be used by regulatory agencies.