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IACS Study on Harmonization of Structural Requirements: Redesign and Structural Analysis of 71 000 TDW Bulk carrier According to CRS Rules

This elaborat presents the work on the second (direct calculation-evaluation) stage/Phase 1 of the Work Plan for Harmonization of IACS Structural Requirements/Minimum Scantling Requirements and involves determination of minimum scantlings based on direct calculations using CRS CLASS SYSTEM. In the direct calculation 2D CREST and 3D MAESTRO models were used to investigate the structural strength of the 3-hold model of the 71000 TDW bulk carrier (IACS test structure) in fulfillment of the requirements of the classification society Croatian Register of Shipping (CRS). An evaluation based on &#8220 ; ; as built&#8221 ; ; scantlings was given in the Report: 1-CRS BULK CARRIER / PRELIMINARY. In this Report iterative redesign procedure was used to determine the minimum scantlings. 3D FEM model has approximately 16258 grid points having around 97548 DOF, 8952 macro-elements (90 girders, 5994 stiffened panels, 294 transverse beams, 1878 additional beams and 696 triangles). Six load cases: LC1-LC6 required by CRS were generated from three loading condition (T&S book) using given weight distribution and adjusted to the required bending moment distribution (still water +wave). All masses (light ship, cargo load, ballast load etc.) were given corresponding accelerations based on the acceleration vector components calculated from the Rules. Dynamic pressures were calculated according to distributions requested by CRS. The CRS PROPOSAL structure was obtained from IACS PROTOTYPE structure (&#8220 ; ; as built&#8221 ; ; scantlings from documentations supplied by the CRS/IACS) by introducing CRS Minimum Requirements and iteratively changing scantlings to satisfy structural safety criteria. (MAESTRO optimization was not used in this Report). The middle hold, fore half of the first hold and aft half of the third hold were analyzed. Aft part of the first hold of the model and fore part of the third hold were excluded from safety evaluation due to influence of boundary conditions. Stress levels were adjusted to CRS Rules. This report presents results for CRS PROPOSAL (deformations, stresses and adequacy parameters) obtained after completing analysis for all six load cases required by CRS. All conclusions are based only on presented load cases. Areas of higher stresses or lower safety with respect to MAESTRO collapse and serviceability criteria, adjusted to CRS safety factors, were clearly identified for detail design consideration.

bulk carrier; CRS Rules; finite elements; MAESTRO modeling; CREST analysis; CRS CLASS SYSTEM

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