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SummaryThe most important degradation effects of ship structures are corrosion and fatigue cracks. Both of these aging effects have clear consequences of increasing the level of stresses and degrading the strength of ship structures for almost all relevant failure modes. This study presents an overview of some recent developments on the aging effects on the ship structural integrity. The analysis of the thickness measurements has been undertaken to improve understanding of the corrosion degradation phenomena and to develop prediction models of aging effects suitable for practical applications in the ship structural design and analysis. The study also deals with the application of the non-linear finite element analysis as a suitable tool for a collapse assessment of uniaxially loaded plates and stiffened panels of ship structures weakened by non-uniform corrosion degradation and fatigue cracks. Experimental studies have also been reviewed to better understand the recently found degradation of mechanical properties of corroded steel, while theoretical calculations have been performed to evaluate consequences of such degradation on the ship structural integrity.

An approach to converting general cargo ship to cement carrier is analysed in the present study, emphasising the structural aspects of the conversion. A comprehensive re-appraisal of the conditions of the ship hull, considering her history and present condition of the structure, is provided. Two case studies are presented where the strength assessment has been performed using 2D sectional and 3D finite element models, generated according to the available hull drawings and thickness measurement reports. The results of the two studies are interpreted with respect to the structural modifications carried out during the conversion process, and some general conclusions are drawn.

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Large engineering structures like ships and other floating structures require reliable and complex computations to ensure their structural integrity over their lifetime. This work presents an analysis of the structural integrity of an aged single-bottom tanker during its towing from Croatia to a scrapheap in Turkey. The ship is subjected to wave loading (corresponding to the global response) and towing force (corresponding to the local response). Computations were performed by a general hydro-structure tool that combines a 3D finite element (FE) structural model and a 3D boundary element (BE) model based on the Rankine panel theory, according to the guidelines of the relevant classification society. Time domain simulations were performed to take account of Froude-Krylov nonlinearities for a wave determined within the Equivalent Design Wave (EDW) approach. After the calculation of wave loading and its transfer to the FE model of a ship structure, the stresses were calculated and compared with the allowable values. The local strength assessment of the ship forecastle deck structure was also performed, considering the prescribed towing force as an imposed load. Both the procedure and the used computational tools are general and can be applied to any kind of ship or other floating structure.