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Publications
Hussein, A.W. and Guedes Soares, C. (2008), “Partial Safety Factors Assessment For Double Hull Tankers Following The New Common Structural Rules”, Proceedings of the 27th International Conference on Offshore Mechanics and Arctic Engineering (OMAE´08), 15-20 June 2008, Estoril, Portugal, ASME, New York, Paper OMAE2008- 57949.
This paper calculates the load and resistance factors for double hull tankers designed according to the new IACS Common Structural Rules. At the beginning the concept of partial safety factor is explained. The scantlings of the three double hull tankers are calculated based on the net scantlings + 50 % of the corrosion addition defined in the CSR, tnet+50. The ultimate strength for the three ships is calculated using progressive collapse method and applying the failure modes defined in the new rules. For one of the tankers, Tanker 2, all the necessary data to calculate the loads are available in the load manual. The still water bending moment is taken from the manual and the wave bending moment is based on ship motion analysis taking account of the extreme value. The calculated loads are compared with the rule design values. Two designs are presented each has different values of loads and the same stochastic model. The reliability for both designs is compared and the partial safety factors are calculated. Sensitivity analysis is made to study the importance of the variables. The rule criterion is applied for both designs to check the compliance with the rule. The three takers are designed according to the rule loads. The reliability is calculated for tnet+50 and the corresponding PSF. To achieve a certain pre defined level of reliability, a design modification factor DMF is applied to the deck plating to adjust the ultimate strength. The loads are assumed to remain unchanged by the design modification factor.
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