engleski

Nonlinear Fine Mesh FEM Analysis of Initially Deformed Decks of Livestock Carrier

Faculty of Mech. Eng. and Naval Arch. and Uljanik Shipyard have performed 3D FEM nonlinear analysis of deck 8, Yard 428 using MAESTRO and NASTRAN software available at University of Zagreb. The coarse-mesh, symmetric, livestock carrier FE model was earlier developed between frames 51 and 176 according to RINA Rules 2000 requirements. Loading conditions were adjusted to R.I.N.A requirements for racking loads. Pressures were calculated by R.I.N.A Rules 2000 Pt B, Ch 5 Sec 4 case d. All masses (light ship, livestock, etc.) were given corresponding accelerations based on the acceleration vector components calculated from Pt B, Ch 5 Sec 3. Livestock masses were concentrated in mesh nodes of the corresponding decks. Details are given in Report ULJ 428 / FINAL. Worst compressive stresses and corresponding pressures were identified from MAESTRO 3D coarse mesh analysis on decks 7-9 between frames 101-146 to be used as demand for presented fine mesh analysis (see Table 1). This Report presents results of nonlinear capability calculations with the fine mesh model of the requested detail:-deck 8 between Fr. 131 and Fr. 141 (see Fig.1). Initial displacements were measured by the Yard for typical deformed field. To calculate minimal capability for flat and initially deformed part of the deck the following analysis were performed using NASTRAN software: (1) bifurcation buckling analysis, (2) geometrically nonlinear incremental and (3) materially and geometrically incremental nonlinear analysis. Boundary conditions to NASTRAN model were adapted from MAESTRO global model. Only in-plane DOF (u, v) were allowed at model boundaries. Pressure and &#61555 ; x loads (demands) were kept constant at maximal recorded level from Table 1. Minimal capability based on fine mesh NASTRAN models for analysis types (1)-(3) are given in Table 2 for undeformed and initially deformed deck segment. It can be concluded that deformed structure satisfies safety requirements since demand &#61555 ; y is bellow structural capability for both types of analysis.

: livestock carrier; fine mesh analysis; bifurcation buckling analysis; material & geometrical nonlinear analysis

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