Assessment of structural integrity of an aged ship during towing in waves

Abstract

Large engineering structures like ships and other floating structures require reliable and complex computations to ensure their structural integrity over the lifetime. This work illustrates an analysis of structural integrity of an aged single-bottom tanker subjected to the wave loading (corresponding to the global response) and towing force (corresponding to the local response). Both the procedure and used computational tools are general and can be applied to any kind of ship or other floating structure, and here the aged ship on its voyage from Croatia to the scrapheap in Turkey is taken as a test case. Computations have been performed by a general hydro-structure tool that combines 3D finite element (FE) structural model and 3D boundary element (BE) model based on Rankine panel theory, according to the guidelines of the relevant Classification Society. Time domain simulations have been performed to take Froude-Krylov nonlinearities into account, for a wave deter-mined 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 are calculated and compared with allowable values. Also, local strength assessment of the ship forecastle deck structure has been performed, considering prescribed towing force as an imposed load.