An advanced technique to adjust hull girder load: Part 1 = generalisation

Abstract

In this study (Part 1), a method is proposed to adjust the loads to achieve the target hull girder load with or without local loads on ships and ship-like structures. Each force or pressure load is referred to as a local load and the sum of forces and moments integrated with respect to the station is referred to as the hull girder load or global load. The hull girder load is composed of axial force (AF), vertical shear force (VSF), horizontal shear force (HSF), torsional moment (TM), vertical bending moment (VBM) and horizontal bending moment (HBM), each of which is related to each other by forces in the x, y and z directions. The adjustment of hull girder loads is required in hull structural analyses with various model extents and boundary conditions. In the whole ship model, it is necessary to implement more accurate hull girder loads and in the cargo hold, fore and aft body model, it is necessary to adjust the hull girder loads calculated from local loads to the target value. In the adjustment of the hull girder load, it is not only important to adjust it more accurately to the target value, but also the distribution of the added load is very important. In general, the hull girder load is adjusted to the target value by adding forces in the x, y and z directions to nodes in the cross section of the hull. If the forces are placed by considering only the position of the nodes, the loads may be concentrated or applied in a different direction from the placement of the elements, resulting in unexpected stresses or deformations in the structural analysis. It is necessary to consider not only the node position but also the size and orientation of the element for force distribution. In this paper, the load distribution at each node is obtained from the product of the directional effective area of the element and the stress field of the beam. The proposed method is validated by adjusting the hull girder loads to the target value for a beam structure with idealised hull. The method proposed in this study will be applied to actual ships in Part 2 (Jang and Kim, 2025a), and its applicability and extendibility are to be verified. This is considered to be beneficial for ship and offshore structural designers including oil/gas and ocean mobilities.