One-dimensional Advanced Beam Models for Marine Structural Applications

Abstract

At preliminary design stage, the global mechanical behavior of large marine vessels such as container ships has previously been analyzed idealizing them as a classical beam. These structures are complex and a classical beam idealization significantly compromises important structural behavior associated with cross section warping or in-plane displacements. On the other hand, 3D Finite Element (FE) models have been utilized which are accurate in capturing these details but pose high computational cost. In present work, structural analyses of marine vessels with realistic boundary conditions have been presented using well-known Carrera Unified Formulation (CUF). Using CUF, higher order theories can be implemented without the need of ad-hoc formulations. The finite element arrays are written in terms of fundamental nuclei for 1D beam elements that are independent of problem characteristics and the approximation order. Thus, refined models can be developed in an automatic manner. In the present work, the beam cross sections are discretized using elements with Lagrange polynomials and the FE model is regarded as Component-Wise (CW), allowing one to model complex 3D features, such as inclined hull walls, floors and girders in the form of components. The work is mainly divided in two parts: Hull in vacuo (in absence of water) and Hull with Hydrostatic Stiffness (in presence of water). The former involves static and dynamic structural analyses of hulls with realistic geometries without the effect of water. The later involves static and dynamic analyses of realistic hull geometries that are supported by buoyancy springs. The stiffness of buoyancy springs is made part of the fundamental nuclei and the corresponding FEM matrices for hydrostatic and hydrodynamic loads are obtained. The hydrodynamic loads have been considered in the form of Radiation Wave loads which include damping and added mass effects. Utilization of Component-Wise (CW) model under hydrodynamic loads has afforded an ease in modelling the complex geometrical configurations such as realistic boat shapes and the dynamic response analyses of aircraft carrier due to moving aircraft. All the analyses have been validated with published literature and their computational efficacy is established through their comparison with the results from commercial code.