Assessment of Residual Ultimate Strength of VLCC According to Damage Extents and Average Compressive Strength of Stiffened Panel

This paper presents the prediction of residual ultimate strength of a very large crude oil carrier considering damage extents due to collision and grounding accidents. In order to determine extents of damage, two types of probabilistic approaches are employed: deterministic approach based on regulations based on ABS [1], DNV [2], and MARPOL [3] and probabilistic approach based on IMO probability density functions (PDFs) (IMO guidelines [4]). Hull girder ultimate strength is calculated using Smith method which is dependent on how much average compressive strength of stiffened panel is accurate. For this reason, this paper uses two different methods to predict average compressive strength of stiffened panel composing hull girder section: CSR formulas and nonlinear FEA. Calculated average compressive strength curves using CSR formulas (IACS [5, 6]) and nonlinear FEA are imported by an in-house software UMADS. Residual ultimate moment capacities are presented for various heeling angles from 0° (sagging) to 180° (hogging) by 15° increments considering possible flooding scenarios. Three regulations and IMO guidelines yield minimum of reduction ratios of hull girder moment capacity (minimum of damage indices) approximately at heeling angles 90° (angle of horizontal moment) and 180° (angle of hogging moment), respectively, because damage area is located farthest from neutral axis.Copyright © 2014 by ASME