International Shipbuilding Progress - Volume 55, issue 1-2

Authors: Guedes Soares, C. | Das, P.K.

Article Type: Other

DOI: 10.3233/ISP-2008-0045

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 1-2, 2008

Authors: Besnier, François | Jian, Ludovic | Murawski, Lech | Weryk, Mateusz

Article Type: Research Article

DOI: 10.3233/ISP-2008-0044

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 3-27, 2008

Authors: Fricke, Wolfgang | Kahl, Adrian

Article Type: Research Article

Abstract: For fabrication reasons, a great part of the joints in ship structures are welded with non-penetrating fillet welds. This implies the risk of fatigue failure originating from the weld root under cyclic loading. A fatigue analysis may be performed using the nominal stress approach, which is rather coarse, and the crack propagation approach, which is less practical due to the high computational effort. Alternatives are offered by the effective notch stress approach, which assumes a fictitious radius at the tip of the non-fused root faces and by a newly developed structural stress approach for weld failures. The latter is outlined …in the paper and applied to the fillet-welded end of a rectangular hollow section (RHS) and to a doubler plate under out-of-plane loads. These represent typical situations with one-sided welds subjected to local throat bending, where fatigue tests have generally shown weld root failure. From the fatigue lives, a design S–N curve based on the structural weld stress is derived. For further verification, the effective notch stress approach is applied to the RHS-joint showing similar results in relation to the design S–N curve as the structural stress approach. Show more

Keywords: Welded joints, fatigue, fillet welds, root failure, structural stress, notch stress

DOI: 10.3233/ISP-2008-0037

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 29-45, 2008

Authors: Chakarov, K. | Garbatov, Y. | Guedes Soares, C.

Article Type: Research Article

Abstract: This work deals with the stress analysis of a longitudinally stiffened welded panel and evaluates the hot spot stress distributions and stress concentration factors that result from different types of imperfections. The hot spot stresses and the stress concentration factors are defined at locations adjacent to the transverse weld. Numerous calculations are performed representing realistic conditions of imperfections and various comparisons of hot spot stress distributions are presented. The stress concentration factor for the cases of pure thickness step changes and for vertical angular imperfections are fit to a quadratic polynomial function.

Keywords: Fatigue, finite element analysis, hot spot stresses

DOI: 10.3233/ISP-2008-0038

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 47-62, 2008

Authors: Guedes Soares, C. | Luís, R.M. | Teixeira, A.P. | Quesnel, T. | Nikolov, P.I. | Steen, E. | Khan, I.A. | Toderan, C. | Olaru, V.D. | Bollero, A. | Taczala, M.

Article Type: Research Article

Abstract: The effects of localized imperfections on the collapse strength of plates are studied by means of finite element analysis performed by different authors. First a benchmark study is performed to assess the accuracy of the results obtained using different codes on the same case study. Afterwards, a parametric study on the effect of the localized imperfections on the collapse strength is performed. Finally, the effect of combining local and global imperfections was studied. It is found that the addition of a localized imperfection changes the collapse strength of the plate, which depends on the amplitude and size of the localized …imperfection change. Show more

Keywords: Initial imperfections, localized imperfections, plate, buckling, collapse strength

DOI: 10.3233/ISP-2008-0039

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 63-85, 2008

Authors: Guedes Soares, C. | Luís, R.M. | Nikolov, P. | Downes, J. | Taczala, M. | Modiga, M. | Quesnel, T. | Toderan, C. | Samuelides, M.

Article Type: Research Article

Abstract: The objective of the paper is to evaluate the ability of simplified structural analysis methods, based on the Smith formulation to predict the ultimate strength of a damaged ship. Such methods are now widely accepted as a reliable and fast way to obtain the longitudinal strength of an intact ship. In order to extend these methods to damaged ships, first a benchmark study on the intact ship was performed in order for the differences between the methods to be evaluated. Afterwards the methods are applied to the same ship section but with damage, which was defined by removing the structural …elements from the affected areas. These, in turn, were obtained from a previous study in which a collision was simulated using a finite element model. Results obtained for the ultimate strength were compared against each other and with the results of the finite element analysis. Aside from some exceptions, the results of the approximate methods agreed well with each other for the intact and damaged conditions. The simplified methods are more conservative than the finite element analysis in hogging while they seem to give a very good approximation to the result for sagging with some of them overestimating this value. Show more

Keywords: Ultimate strength, damaged hull girder, Smith method, longitudinal strength, vertical bending moment

DOI: 10.3233/ISP-2008-0040

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 87-107, 2008

Authors: Garbatov, Y. | Guedes Soares, C.

Article Type: Research Article

Abstract: Recently developed corrosion wastage models for marine structural applications are reviewed. A non-linear corrosion model is applied to measured service data of the deck of bulk carriers in order to evaluate the model parameters that adjust to the corrosion rates for those ship structures. Comparisons with corrosion wastage in tankers are given and discussed.

Keywords: Corrosion, ship hull, deterioration

DOI: 10.3233/ISP-2008-0041

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 109-125, 2008

Authors: Ehlers, Sören | Broekhuijsen, Joep | Alsos, Hagbart S. | Biehl, Florian | Tabri, Kristjan

Article Type: Research Article

Abstract: Simulations of the collision response of three different ship side structures are performed using the finite element method. The aim is to obtain a force–penetration curve based on the inner mechanics without considering outer dynamics. Respective structures were previously tested in large scale under the right angle ship–ship collision with a bulbous bow and these experiments were used to validate the simulations. The analysis focus is to determine the influence on the collision results from different failure criteria including the mesh size sensitivity. This paper applies the Germanischer Lloyd (GL) criterion based on thru thickness plastic strain, the criterion based …on studies of Peschmann and the Rice–Tracey and Crockcroft–Latham (RTCL) criterion. The comparison of results attained here with the experimental results brings an insight into the sensitivity of the failure criteria. The final conclusion of this work is the performance of the studied failure criteria and further guidelines for collision or grounding simulations. Show more

Keywords: FEM, non-linear, LS-DYNA, failure criteria, large scale experiments

DOI: 10.3233/ISP-2008-0042

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 127-144, 2008

Authors: Samuelides, M.S. | Tabri, K. | Incecik, A. | Dimou, D.

Article Type: Research Article

Abstract: Since the late fifties, when the first nuclear powered merchant ships were designed, collision research has been focused on the establishment of models for the prediction of the damage of the side of a ship involved in a ship–ship collision. Such models have been used to assess the performance of the struck ship in case she is involved in a collision. Further it was and it is still highly desirable to develop design tools which could provide guidance for the construction of ship hulls which will minimize as far as possible the risk in case of a collision. In order …to assess the collision behaviour of a ship, there is a need to test her under specific collision incidents, which are described by a number of parameters, such as the particulars of the striking ship including the stiffness of her bow, the speeds and relative orientation of the two vessels, sea conditions, etc. The assessment methodologies are deterministic, i.e. they are based on one or a few severe collision scenarios, or probabilistic, i.e. they consider distribution functions of one or more collision parameters. The paper presents and discusses existing codes concerning collision scenarios for floating and fixed marine structures, presents data that can be used for the determination of the level of the loading that a ship may experience if she is involved in a collision and gives examples of relevant calculations. Show more

Keywords: Ship collision, collision scenarios, accidental limit state, design against collision

DOI: 10.3233/ISP-2008-0043

Citation: International Shipbuilding Progress, vol. 55, no. 1-2, pp. 145-162, 2008