Stipe Tomašević

Fatigue Analysis of Structural Details of an Oceangoing LPG Ship

Structural details of ship structures are prone to fatigue damage mainly due to high-cycle wave load and low-cycle cargo loading/unloading. Full stochastic fatigue analysis of selected structural details on an oceangoing 6500 cbm LPG ship is presented. A critical Y-joint of longitudinal bulkhead and bilobe tank shell as well as double-bottom girder details are selected due to different reasons. The eccentricity of the Y-joint, leads to significant stress concentration. Saddle supports of gas tanks cause stress concentration in ship double bottom due to weight and dynamic loads. Wave load on ship structure is calculated using linear strip theory for ship in ballast condition and full ship. Wave load is transferred to ship finite element model and notch structural stresses are determined using finite element analysis. Stochastic fatigue analysis is then performed, taking into account sailing route and other ship operational parameters. Finally, fatigue damage summation is done and results are discussed.

Hydroelastic Aspects of Large Container Ships

The importance of hydroelastic analysis of large and flexible container ships of today is pointed out. A methodology for investigation of this challenging phenomenon is drawn up and a mathematical model is worked out. It includes definition of ship geometry, mass distribution, structure stiffness, and combines ship hydrostatics, hydrodynamics, wave load, ship motion and vibrations. Based on the presented theory, a computer program is developed and applied for hydroelastic analysis of a flexible segmented barge for which model test results of motion and distortion in waves have been available. A correlation analysis of numerical simulation and measured response shows quite good agreement of the transfer functions for heave, pitch, roll, vertical and horizontal bending and torsion. The developed tool is furthermore used for hydroelastic analysis of a large container ship.© 2008 ASME