Modeling of ship’s side shell openings in global finite element models

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Avi, Eero
dc.contributor.advisor Niemelä, Ari Kaldoja, Martin 2017-10-30T07:55:50Z 2017-10-30T07:55:50Z 2017-09-25
dc.description.abstract This thesis presents and investigates two common techniques of modeling large periodic side shell openings in global finite element models for evaluation of passenger ship hull girder static response in early design phase. The first technique is based on homogenization of side shell structure and modeling side shell openings with homogenized orthotropic material using 4-noded and 8-noded shell elements. Second technique is direct modeling of side shell openings using coarse mesh, where cost of simplification to geometry and mesh size is studied. The proposed techniques are validated with respect to 3D fine mesh analysis in two cases. First, periodic side shell model is studied for evaluation of correct in plane response under uniform axial and shear loading. Second, the techniques are investigated in a box-like ship under 4-point bending load. Accuracy of both techniques is evaluated by means of hull girder deflection, longitudinal deck forces and side shell vertical shear forces. In addition, the performance in border of periodic grid and at areas of high strain gradients is investigated. The results indicate that equivalent orthotropic modeling of both central and offset openings gives accurate global deflection and longitudinal bending response in a simple model where strain gradients are small. When significant strain gradients are introduced e.g. where internal longitudinal bulkheads are discontinuous, the deflection and longitudinal bending response accuracies are compromised. Local response of orthotropic model is less accurate and especially compromised at edges of periodic grid and areas of high strain gradient. Additional local errors arise due to micropolar behavior of offset openings, where the equivalence is only achieved in forces but not in moments due to application of classical theory of elasticity. No significant difference in response is observed whether 4- or 8-noded elements are applied. For coarse mesh modeling a sensitivity analysis is performed taking account effect of simplification of structure and mesh size. A reasonable compromise between modeling effort, computational cost and accuracy is found at 4x4 elements per opening. Despite being stiffer in uniformly loaded periodic side shell model, the accuracy of coarse mesh modeling is shown to be reliable in application to box-like ship, where performance is not significantly affected by strain gradients and boundary effects. en
dc.format.extent 7+64+4
dc.language.iso en en
dc.title Modeling of ship’s side shell openings in global finite element models en
dc.type G2 Pro gradu, diplomityö fi Insinööritieteiden korkeakoulu fi
dc.subject.keyword finite element analysis en
dc.subject.keyword cruise ship en
dc.subject.keyword equivalent orthotropic modeling en
dc.subject.keyword coarse mesh modeling en
dc.identifier.urn URN:NBN:fi:aalto-201710307320
dc.programme.major Marine Technology fi
dc.programme.mcode K3005 fi
dc.type.ontasot Master's thesis en
dc.type.ontasot Diplomityö fi
dc.contributor.supervisor Romanoff, Jani
dc.programme Konetekniikan koulutusohjelma fi
local.aalto.electroniconly yes
local.aalto.openaccess no

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