PSI - Issue 48

Nikola Momčilović et al. / Procedia Structural Integrity 48 (2023) 12 – 18 N. Mom č ilovi ć et al / Structural Integrity Procedia 00 (2023) 000 – 000

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Fig. 5. Ultimate strength of new ship, pitting corrosion affected and uniform corrosion affected ship in sagging condition.

Fig. 6. Ultimate strength of new ship, pitting corrosion affected and uniform corrosion affected ship in hogging condition.

5. Conclusions The paper presents the methodology and the results using the incremental-iterative progressive collapse analysis (PCA) for the determination of ultimate strength of new ship and the ship with scantlings diminished by either pitting or uniform corrosion. For the purpose of analysis, a typical 180 m long bulk carrier is considered affected by the severe corrosion. Pitting corrosion is modeled by incorporating an actual volume loss of the element, which is defined by pitting intensity degree and corrosion intensity degree. This determined the equivalent reduction of thickness. Uniform corrosion is analysed by excluding the diminished part of the element thickness. Both have influenced the slenderness ratio of the element and consequently, an ultimate strength. Results showed that ultimate strength of ageing bulk carrier is significantly reduced by both pitting and uniform corrosion. In case in which just double bottom and top side tank are corroded, ultimate strength of the ship is reduced by:  5.5% (in sagging condition) and 21.5% (in hogging condition) – for pitting equivalent thickness reduction by 16%,  9% (in sagging condition) and 14% (in hogging condition) – for uniform corrosion thickness reduction by 25%. In case of all elements of the cross section are assumed as corroded, ultimate strength of the ship is reduced by:  30% (in sagging condition) and 28% (in hogging condition) – for pitting equivalent thickness reduction by 16%,  14% (in sagging and hogging condition) – for uniform corrosion thickness reduction by 25%, The results show that ship ageing effects, represented by pitting and uniform corrosion, can be fused into PCA and should not be neglected in structural analyses of ships. Furthermore, the ship ultimate strength is not one of a kind,