engleski

Analysis of structural details of car carrier -4300 cars

Faculty of Mech. Eng. and Naval Arch. and Uljanik Shipyard have performed 3D FEM analysis of Yard 437-439 using MAESTRO software available at University of Zagreb. The coarse-mesh, full-asymmetric, global car carrier FE model was developed (Pt B, Ch 7, App 2). It simultaneously provides boundary conditions for fine mesh analysis of the critical areas on (1) watertight bulkhead (Fr.147) under transverse racking induced forces and (2) Fr 106 corner of side door. Full ship 3D FEM model has 47 064 DOF and 18 462 macroelements (10164 stiffened panels and 8298 beams). Loading condition 3 (Cars on decks 1 to 11, 100% fuel and stores) was adjusted to R.I.N.A requirements for racking (Pt B, Ch 5, Sections 3-5). Pressures were calculated by R.I.N.A Rules. All masses (light ship, cars, etc.) were given corresponding accelerations based on the acceleration vector components calculated from the Rules (Pt B, Ch 5, Section 3). Car masses were concentrated in mesh nodes of the corresponding decks. Fine mesh models for Detail Stress Analysis (DSA) using "top down approach" were developed. Boundary conditions to DSA models were automatically transferred from MAESTRO global model. Stress levels were adjusted to R.I.N.A Rules (Pt B, Ch 7, Section 4). Ship satisfies R.I.N.A racking requirements. Detail analysis : (1) Brackets on Fr147. were highly stressed ( &#61555 ; vonMises, max = 226 N/mm2) and adequate material and weld quality should be assured. The bracket's free end preparation should be performed to avoid crack initiation. Original and modified detail were analyzed using the fine mesh models for C.L. bracket. Modified model gives higher safety in region of interest. Opposite side with suggested modification is expected to have same stress levels. Fine mesh model could also be developed. (2) Coarse mesh model is checked for Fr.106 region to access stress levels. Achieved levels are below RINA requirements but only fine mesh model can detect stress concentrations, if any.

Car carrier; finite elements; MAESTRO modeling; detail stress analysis

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