Shear-induced secondary bending response at balcony opening of passenger ship

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School of Engineering | Master's thesis
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Date
2011
Major/Subject
Laivanrakennusoppi
Mcode
Kul-24
Degree programme
Language
en
Pages
57
Series
Abstract
Passenger ships with large balcony openings have complicated structural behaviour which does not follow the basic beam theory. Moreover, plates around the balcony opening can locally bend and therefore, experience large shear-induced secondary normal stresses whose values are much higher and more complicate to evaluate compared purely on the normal stress distribution over the cross-section of the hull girder. Currently, hull girder strength assessment is based on FE-analyses. Such kind of approach is time-consuming and therefore, does not fit with the structural optimization procedures. Thus, for concept design stage, simplified method should be developed for rapid response evaluation around the balcony openings. The aim of the thesis is to develop a simplified approach to estimate secondary response around balcony openings. It is assumed that this simplified calculation model with the global response analysis can considerably reduce the time spent on the nominal stress evaluation. The purpose of the simplified approach is to estimate the nominal stresses which can be later used with proper stress concentration factor in fatigue strength analyses at the ship concept design stage. Simplified approach is based on Timoshenko beam elements and calculations are conducted with FE-method. Deformation shape and boundary conditions for simplified beam model are studied and applied from global 3D FE-analyses of the hull girder. Simplified beam model is validated with corresponding plate model as this is relevant for ship side structure. Finally, response around balcony openings from different ship regions is estimated with simplified approach and results are compared with the global 3D FE-analyses. As a result, it is revealed that normal stresses are induced by shear and thus, considered as a secondary bending response. In conclusion, comparisons of normal stresses prove that simplified approach is valid for response evaluation in certain locations around ship balcony openings.
Description
Supervisor
Varsta, Petri
Thesis advisor
Romanoff, Jani
Naar, Hendrik
Keywords
loading in ship design, 4-point bending, balcony opening, passenger ship with narrow superstructure, shear-induced secondary bending response, FE.method, Timoshenko beam theory
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