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Turku, Finland

Melk K.,Aalto University | Romanoff J.,Aalto University | Remes H.,Aalto University | Varsta P.,Aalto University | And 2 more authors.
Analysis and Design of Marine Structures - Proceedings of the 4th International Conference on Marine Structures, MARSTRUCT 2013 | Year: 2013

Present paper investigates the shear-induced secondary normal stresses in the balcony openings of modern passenger vessel with narrow superstructure. The investigation is carried out using Finite Element Method. Two loading schemes are considered, i.e. cosine shape loading simulating realistic loading caused by waves and four-point bending load enabling deeper analysis on the shear-induced responses. The investigation shows that the shear-induced normal stresses have considerable effect to the overall stress state around balcony openings. It also shows that the passenger ship hull girder shear response is extremely complicated phenomenon and therefore entire ship length needs to be modeled when assessing the bending response of the ship. © 2013 Taylor & Francis Group. Source

Suominen M.,Aalto University | Karhunen J.,University of Oulu | Bekker A.,Stellenbosch University | Kujala P.,Aalto University | And 2 more authors.
Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC | Year: 2013

The presence of rich natural resources in Arctic waters continuously raises interest in marine operations in ice. Despite the availability of several full-scale measurements in ice-infested waters, knowledge of the impact of ice-structure interaction on the ship's hull and propulsion system as well as on the comfort of the crew and passengers on board is limited. This can be attributed to: (1) the fact that the effects of ice loading on the ship hull has not yet been related to prevailing ice conditions, (2) ice loading and the related response of the propulsion system is an almost unknown process and (3) vibration levels resulting from ship-ice interaction are not known. To increase the knowledge in these fields, full-scale measurements were conducted on the PSRV S.A. Agulhas II in the Baltic Sea during March 2012. Measurements on the following were obtained: (1) ice loads on the ship hull and propulsion system, (2) ice-induced structural vibration and noise, (3) whole-body vibration comfort, (4) ship dynamics in ice, (5) global ice loads, (6) underwater noise and (7) mechanical and physical sea ice properties. Furthermore, the effect of ship operations on the loads induced by ice on the ship hull was studied during a variety of ship manoeuvres. This paper focuses on selected aspects of the conducted full-scale measurements, including: (1) the ice loading on the ship hull and propulsion system, (2) human comfort on board (3) mechanical ice property measurements, (4) the effect of ship operations on the maximum ice loads on different hull areas, (5) the natural frequencies and damping effects of the propeller shaft and (6) the possibility of the resonance of the propeller shaft's due to the sequential propeller blade impacts with ice. Source

Romanoff J.,Aalto University | Jelovica J.,Aalto University | Avi E.,STX Finland | Niemela A.,STX Finland
Computational Methods in Marine Engineering V - Proceedings of the 5th International Conference on Computational Methods in Marine Engineering, MARINE 2013 | Year: 2013

The present paper discusses on the modeling of ship deck panels at concept design stage using Equivalent Single Layer (ESL) plate theory. First order shear deformation theory is utilized that enables modeling of one-side stiffened plates used traditionally in shipbuilding, but also double-skinned structures such as sandwich plates and composite structures. Interaction between the plate element and supporting girders is modeled using offset beams. The static, vibration, bifurcation buckling and post-buckling response are considered. The validation is done with fine mesh FE-analyses based on modeling the actual 3D topology with shell elements. The paper shows that ESL is very efficient way to model and optimize the ship structure where differences of scale, as well as the complexity of the geometry, cause difficulties for the Finite Element discretization as well as to the solution. The benefit of the method is that FE-mesh needs to be created only once. This enables optimization during the design by changing only the equivalent stiffness properties of the beams and plates leaving the mesh unchanged. Source

Avi E.,STX Finland | Lillemae I.,Aalto University | Romanoff J.,Aalto University | Niemela A.,STX Finland
Ships and Offshore Structures | Year: 2015

This paper presents an equivalent shell element for assessing the ship global and local static and vibration response in early design phases. The element provides a computationally economic tool for global analysis and the same mesh can be used in primary, secondary and tertiary level. The stiffened panel is considered as a three layer laminate element, where the first layer represents the plate, the second layer represents the stiffener web and the third layer represents the stiffener flange. The layers are described as 2D iso- and orthotropic materials, where elasticity matrices are found by applying the rule of mixtures. The element includes the in-plane, membrane-bending coupling, bending and additionally also shear stiffness, which follows the Reissner-Mindlin plate theory for anisotropic homogenous shells. The local plate bending response between the stiffeners is considered as well. The developed shell formulation has been implemented in commercial FE software FEMAP with NX Nastran and demonstrated through two case studies. Results are validated against 3D fine mesh quasi-static and vibration analyses and very good agreement is observed. © 2014 Taylor & Francis. Source

Romanoff J.,Aalto University | Remes H.,Aalto University | Varsta P.,Aalto University | Jelovica J.,Aalto University | And 4 more authors.
Ships and Offshore Structures | Year: 2013

The paper investigates the interaction between the hull and the superstructure in optimised passenger ships when exposed to bending loads. The coupled beam theory was applied to extend the basic beam theory to take into account the vertical and shear stiffness between various decks. Optimisation of passenger ships with respect to weight and vertical centre of gravity (VCG) is carried out to create a set of Pareto-optimal solutions. The responses of these designs are compared in detail. The investigation shows that vertical and shear coupling between different decks significantly affect the response of the passenger ships and changes load-carrying mechanism of the hull girder. In the weight optimal design, the vertical bending moment is shared equally by the hull and the superstructure, while in the VCG optimal design, the neutral axis approaches bottom plating of the ship, considerably increasing the share of load carried by the superstructure. This means that the global response evaluation needs to include vertical and shear coupling along the length of the ship, and thus, the simplified two-dimensional section models are not adequate for the conceptual design of passenger ship structures. © 2013 Taylor & Francis. Source

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