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Publicações
Corak, M., Parunov, J. e Guedes Soares, C. (2018), “Structural reliability analysis of container ships under combined wave and whipping loads”, Journal of Ship Research, Vol. 62(3), pp. 115-133
A practical methodology for structural reliability assessment of ultra large container ships is proposed in the paper. The commonly used limit state function for structural reliability analysis of oil tankers and bulk carriers is extended to take into account the whipping response due to the bow flare slamming. Ultimate vertical bending moment capacity of hull girder is considered as a fundamental safety variable in the limit state function, while the stochastic model of the loads consists of static still water bending moments, low frequency rigid-body vertical wave bending moments and high frequency whipping bending moments. The stochastic model of still water bending moment for one of the studied ships is obtained from actual bending moments recorded by the on-board loading computer in two years of operation. Linear vertical wave bending moment is calculated by a 3D panel seakeeping code, using IACS recommendation No.34 for the computation of extreme global wave loads. The non-linear correction of linear wave bending moment is obtained from the recent IACS Unified Requirement S11A for longitudinal strength of container ships. Impulsive loading is modelled by von Karman added mass variation method while transient dynamic hull girder response is analysed by Timoshenko beam finite elements. Load combinations between extreme still water and vertical wave bending moments, as well as between extreme low- and high-frequency vertical wave bending moments are considered. The structural reliability analysis of two container ships of different sizes is performed using first order reliability method, in order to observe differences in safety levels due to different ship sizes. Safety indices are compared to the IMO recommendations for Double-Hull Oil Tankers in order to have credible basis for assessing the obtained results. An extensive sensitivity and parametric study is performed, accounting for various operational, environmental and modelling uncertainties, as well as for corrosion degradation. The presented study may be useful for classification societies in further development of recently introduced IACS Unified Requirements for longitudinal strength of container ships.
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