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IACS Study on Harmonization of Structural Requirements: Redesign and Structural Analysis of 300 000 TDW VLCC According to CRS Rules

This elaborat presents the work on the Phase 1 Stage 2 (direct calculation-evaluation) 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 300 000 TDW crude oil tanker (IACS - VLCC test structure) in fulfillment of the requirements of the classification society Croatian Register of Shipping (CRS). An evaluation based on &#8216 ; as built&#8217 ; scantlings was given in the Report: 1-CRS-TANKER PRELIMINARY. In this Report iterative redesign procedure (no formal MAESTRO optimization) was used to determine the minimum scantlings. 3D FEM model has approximately 31146 grid points having around 186 876 DOF, 19244 macro-elements( 128 girders, 9994 stiffened panels, 1126 transverse beams, 2608 pillars, 3942 additional beams and 1446 triangles). Eleven loadcases: LC1-LC11 required by CRS were generated from six loading conditions (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. External pressures were calculated according to distributions requested by CRS. The CRS PROPOSAL structure was obtained from IACS PROTOTYPE structure (&#8216 ; as built&#8217 ; scantlings from documentation supplied by the CRS/IACS) by introducing CRS Minimum Requirements and iteratively changing scantlings to satisfy structural safety criteria. Only middle hold was analyzed, first hold and the third hold, were excluded from safety evaluation due to influence of boundary conditions. Stress levels were adjusted to CRS Rules. This Report present results for CRS PROPOSAL (deformations, stresses and adequacy parameters) obtained after completing analysis for all eleven loadcases required by CRS. All conclusions were based only upon presented loadcases. Areas of higher stress or lower safety with respect to the MAESTRO collapse and serviceability criteria, adjusted to CRS safety factors, were clearly identified for the detail design considerations.

crude oil tanker; CRS Rules; finite elements; MAESTRO modeling; CREST analysis; CRS CLASS SYSTEM

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