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Global hydroelastic analysis of ultra large container ships by improved beam structural model
Ivo Senjanović,Nikola Vladimir,Marko Tomić,Neven Hadžić,Šime Malenica 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
Some results on the hydroelasticity of ultra large container ships related to the beam structural modeland restoring stiffness achieved within EU FP7 Project TULCS are summarized. An advanced thin-walled girder theorybased on the modified Timoshenko beam theory for flexural vibrations with analogical extension to the torsionalproblem, is used for formulation of the beam finite element for analysis of coupled horizontal and torsional ship hullvibrations. Special attention is paid to the contribution of transverse bulkheads to the open hull stiffness, as well as tothe reduced stiffness of the relatively short engine room structure. In addition two definitions of the restoring stiffnessare considered: consistent one, which includes hydrostatic and gravity properties, and unified one with geometric stiffnessas structural contribution via calm water stress field. Both formulations are worked out by employing the finiteelement concept. Complete hydroelastic response of a ULCS is performed by coupling 1D structural model and 3Dhydrodynamic model as well as for 3D structural and 3D hydrodynamic model. Also, fatigue of structural elementsexposed to high stress concentration is considered.
Analytical procedures for torsional vibration analysis of ship power transmission system
Senjanović,, Ivo,Hadž,ić,, Neven,Murawski, Lech,Vladimir, Nikola,Alujević,, Neven,Cho, Dae-Seung Elsevier 2019 ENGINEERING STRUCTURES Vol.178 No.-
<P><B>Abstract</B></P> <P>In this paper two relatively simple analytical procedures for free and forced torsional vibration analysis of ship power transmission systems are developed. In the first, approximate procedure, the shaft line is modelled as a two-mass system and analytical solution of the differential equations of motion is given. In the second one, a multi degree of freedom (d.o.f.) problem of the complete propulsion system is solved by the Rayleigh-Ritz method. A special attention is paid to the determination of the contribution of each cylinder to the primary and secondary engine torques by taking into account the firing order. The application of the two procedures is illustrated in the case of a typical propulsion system of a merchant ship with a slow-speed main engine connected directly to the propeller by a relatively short shaft line. The obtained results are verified by a comparison with measurements. All classification societies require calculation of the propulsion system operating parameters, but they do not provide simplified formulae for vibration analysis. The outlined analytical procedures can be used for the estimation of torsional vibration of the shaft line in the preliminary ship design stage as well as for ships in service.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Condensed two-mass model of shaft line. Analytical solution of diff. eqs. of motion. </LI> <LI> Simplified multi-mass model of shaft line. Rayleigh-Ritz method. Analytical solution. </LI> <LI> Formulation of cylinder torque and engine primary and secondary torque. </LI> <LI> Physically based transfer factor of engine excitation to shaft response. </LI> <LI> Comparison with FEM. Verification by measurement. High accuracy. </LI> </UL> </P>