Hull Girder Loading

Abstract

Ship hull girder loads consist of static and dynamic components. The most significant of these components are the still-water bending moments and shear forces. The still-water component results from the difference between the distributions of the various weight items and the distribution of the supporting buoyancy forces along the ship length. The weight items include light weight of the ship, cargo weight and weight of consumables. The dynamic loads include wave induced hydrodynamic loads, sloshing, slamming, inertia loads due to vessel motion and impact loads. The dynamic wave-induced loads include the vertical and horizontal shear forces, bending moments and torsional moments. Wave loads are normally evaluated by means of one of the two methods: design wave method or spectral analysis method. The latter method is based on either short or long term predictions, transfer functions, and the assumption that loads are linearly dependent on wave height. Depending on the loading condition of the vessel, the still-water bending moments and shear forces are determined using the published rules of classification societies. A more detailed analysis is required when determining the dynamic aspects of the hull girder loads for extreme sea conditions that the vessel is bound to encounter over its lifetime.