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C. Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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Prediction of vertical responses of a container ship in abnormal waves
Ocean Engineering, 2016Co-Authors: Suresh Rajendran, Nuno Fonseca, C. Guedes SoaresAbstract:Abstract A body-nonlinear time domain code based on strip theory is used to calculate the vertical ship responses of a containership in extreme sea conditions. The numerical method calculates the radiation forces based on Cummins formulation. A practical engineering approach is followed for calculation of the radiation/diffraction forces for instantaneous wetted surface of the hull. The Froude–Krylov and hydro static forces are also calculated for instantaneous wetted surface area of the hull. The numerical method calculates the vertical responses of a container ship in abnormal waves embedded in a real deterministic sea and the results are compared with the model test data. Results obtained from the numerical code that uses body-nonlinear hydrodynamic and hydrostatic forces are compared with results from another code that uses linear radiation/diffraction force and body-nonlinear Froude–Krylov and hydrostatic force. Time series of the vertical ship motion, vertical bending moment at the midship, and the relative motion at the bow are calculated and compared. Additionally, short term distribution of peaks of the vertical motion and bending moment, and the largest vertical bending moment peaks are analyzed. It is observed that the body nonlinear radiation/diffraction forces significantly improve prediction of the ship responses in extreme waves.
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Effect of the Nonlinear Vertical Wave-induced Bending Moments on the Ship Hull Girder Reliability
Ocean Engineering, 2016Co-Authors: B. Gaspar, A.p. Teixeira, C. Guedes SoaresAbstract:In the present paper the effect of the nonlinear vertical wave-induced bending moments on the ship hull girder reliability is evaluated. A chemical tanker for which the nonlinearity of the vertical wave-induced bending moments was found to be significant is adopted as case study. The nonlinear effects on the vertical wave-induced bending moments of the chemical tanker are accounted for in the reliability assessment problem through model correction factors, which are estimated using direct calculation methods based on linear and nonlinear strip theory formulations and the most likely response wave method. It is verified that the design formulation presently used to define the hull girder vertical wave-induced bending moments underestimates the magnitude of the nonlinear effects. The more accurate predictions provided by the direct calculations methods show that the actual hull girder reliability in sagging is significantly smaller. Possible modified design solutions for the midship cross-section of the chemical tanker are evaluated in order to demonstrate the impact of the increase of the nonlinear vertical wave-induced bending moment in sagging in terms of structural design criteria.
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Experimental strength assessment of thin steel plates with a central elongated circular opening
Journal of Constructional Steel Research, 2016Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract This work assesses the ultimate strength of experimentally tested steel plates with a large central elongated circular opening, subjected to uni-axial compressive load. A series of experimental tests have been carried out on plates that were part of a real structure, which represents a scaled midship section of single hull tanker ship, tested in a corrosive environment in direct contact with seawater. One elongated circular opening shape with different sizes is analyzed and the effect of the opening size on the ultimate strength is investigated. The force–displacements relationships are presented and the dissipated energy is analyzed. Stress–strain relationships, resilience and toughness have been evaluated. The collapse modes are discussed and the ultimate strength has been compared with recently published studies showing a good agreement in the trend.
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Experimental assessment of the ultimate strength of a box girder subjected to severe corrosion
Marine Structures, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract The objective of this paper is to describe the experimental assessment of the ultimate strength of a severely corroded box girder subjected to a uniform bending moment resulting from four-point loading. Three box girders that could simulate the behaviour of midship sections have been deteriorated in corrosive seawater environment to simulate different levels of corrosion degradation of ageing ship structures. During the deterioration process, various parameters have been controlled and the total weight lost was registered. Corroded plate thicknesses have been measured in 212 points and a statistical analysis has been performed. The resulting corrosion wastage has been fitted by a non-linear time variant degradation model. The experimental results of the ultimate strength test of a severely corroded box girder subjected to a four-point loading have been analysed. The load-displacement and moment-curvature relationship is discussed, different failure modes are identified, and the strain gauges readings are analysed.
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Reliability-Based Design of the Primary Structure of Oil Tankers
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 1997Co-Authors: G. Casella, M. Dogliani, C. Guedes SoaresAbstract:The present paper describes the reliability analysis carried out for two oil tanker-ships having comparable dimensions but different design. The scope of the analysis was to derive indications on the value of the reliability index obtained for existing, typical and well designed oil tankers, as well as to apply the tentative rule checking formulation developed within the CEC-funded SHIPREL Project. The checking formula was adopted to redesign the Midships section of one of the considered ships, upgrading her in order to meet the target failure probability considered in the rule development process. The resulting structure, in view of an upgrading of the steel grade in the central part of the deck, lead to a convenient reliability level. The results of the analysis clearly showed that a large scatter exists presently in the design safety levels of ships, even when the Classification Societies` unified requirements are satisfied. A reliability based approach for the calibration of the rules for the global strength of ships is therefore proposed, in order to assist designers and Classification Societies in the process of producing ships which are more optimized, with respect to ensured safety levels. Based on the work reported in the paper, the feasibility andmore » usefulness of a reliability based approach in the development of ship longitudinal strength requirements has been demonstrated.« less
Yordan Garbatov - One of the best experts on this subject based on the ideXlab platform.
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Experimental strength assessment of thin steel plates with a central elongated circular opening
Journal of Constructional Steel Research, 2016Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract This work assesses the ultimate strength of experimentally tested steel plates with a large central elongated circular opening, subjected to uni-axial compressive load. A series of experimental tests have been carried out on plates that were part of a real structure, which represents a scaled midship section of single hull tanker ship, tested in a corrosive environment in direct contact with seawater. One elongated circular opening shape with different sizes is analyzed and the effect of the opening size on the ultimate strength is investigated. The force–displacements relationships are presented and the dissipated energy is analyzed. Stress–strain relationships, resilience and toughness have been evaluated. The collapse modes are discussed and the ultimate strength has been compared with recently published studies showing a good agreement in the trend.
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Experimental assessment of the ultimate strength of a box girder subjected to severe corrosion
Marine Structures, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract The objective of this paper is to describe the experimental assessment of the ultimate strength of a severely corroded box girder subjected to a uniform bending moment resulting from four-point loading. Three box girders that could simulate the behaviour of midship sections have been deteriorated in corrosive seawater environment to simulate different levels of corrosion degradation of ageing ship structures. During the deterioration process, various parameters have been controlled and the total weight lost was registered. Corroded plate thicknesses have been measured in 212 points and a statistical analysis has been performed. The resulting corrosion wastage has been fitted by a non-linear time variant degradation model. The experimental results of the ultimate strength test of a severely corroded box girder subjected to a four-point loading have been analysed. The load-displacement and moment-curvature relationship is discussed, different failure modes are identified, and the strain gauges readings are analysed.
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Compressive strength assessment of a moderately corroded box girder
Marine Systems & Ocean Technology, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:This paper presents the results of the experimental test of a multispan corroded stiffened box girder subjected to moderate corrosion deterioration. The experiment is carried out to study the compressive collapse strength of a box girder subjected to four-point loading, which results in a constant vertical bending moment. The box girder reproduces the behaviour of a midship hull structure. The collapse modes are discussed, showing the effect of corrosion on the final collapse mode and the release of the residual stresses. The load-displacement, moment-curvature as well as the strain readings are presented and analysed. The ultimate bending moment results have been compared with some existing formulas, showing the lack of the prediction of the behaviour of the corroded structures.
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Reliability of maintained ship hulls subjected to corrosion and fatigue under combined loading
Journal of Constructional Steel Research, 1999Co-Authors: C. Guedes Soares, Yordan GarbatovAbstract:A formulation is presented for the assessment of the reliability of longitudinal members of a ship hull as a result of fatigue and corrosion under combined loading. The model allows for the existence of multiple cracks and it accounts for the crack growth process. The time dependent degrading effect of corrosion and crack growth on the midship section modulus are modelled as random processes. The reliability is predicted by a time variant formulation and, using a two-failure criterion, the effects of maintenance actions in increasing the reliability are shown. The sensitivity of the reliability estimates with respect to different loading combinations is also studied. The formulation has been applied to a tanker.
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Reliability assessment of maintained ship hulls with correlated corroded elements
Marine structures, 1997Co-Authors: C. Guedes Soares, Yordan GarbatovAbstract:This paper reviews the factors that affect the corrosion rate of the ship hull girder. It is shown that corrosion rates vary as a function of the location of the element in the structure, of the ocean area and type of ballast tank and steel. However, the corrosion rate in elements that are subjected to similar conditions is highly correlated. A time-variant formulation is proposed including the correlation between the corrosion rates in neighbouring elements in modelling the degrading effect that corrosion has on the reliability of ship hulls. The effect of corrosion is represented as a time-dependent decrease of plate thickness that affects the midship section modulus. One repair policy was considered and the example results show the effect of plate replacement when its thickness reaches 75% of the original value. The results also illustrate how the limit value of the thickness in the repair criteria influences the reliability and the decision about repair actions. This is also shown for the effect of different corrosion rates, inspection intervals, and allowable stresses.
C. Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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Hull girder reliability using a Monte Carlo based simulation method
Probabilistic Engineering Mechanics, 2013Co-Authors: Boris Gaspar, C. Guedes SoaresAbstract:This paper presents a hull girder reliability assessment using a Monte Carlo based simulation method. The simulation method used was developed for component and system reliability problems and provides accurate estimates for the failure probability with reduced computational cost as compared to crude Monte Carlo simulation. The reliability assessment is performed considering as possible failure modes the ultimate collapse of the midship cross section in vertical bending or its local failure due to yielding of the material or buckling collapse of one of its structural elements. The local failure mode was formulated as a system reliability problem. The incremental-iterative method for progressive collapse analysis adopted in the IACS-CSR design rules for oil tankers and bulk carriers was adopted as strength assessment model. Due to the capabilities of the simulation method to deal with high-dimensional problems the geometric and material properties of the midship cross section elements were explicitly included in the simulation as basic random variables.
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Compressive strength assessment of a moderately corroded box girder
Marine Systems & Ocean Technology, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:This paper presents the results of the experimental test of a multispan corroded stiffened box girder subjected to moderate corrosion deterioration. The experiment is carried out to study the compressive collapse strength of a box girder subjected to four-point loading, which results in a constant vertical bending moment. The box girder reproduces the behaviour of a midship hull structure. The collapse modes are discussed, showing the effect of corrosion on the final collapse mode and the release of the residual stresses. The load-displacement, moment-curvature as well as the strain readings are presented and analysed. The ultimate bending moment results have been compared with some existing formulas, showing the lack of the prediction of the behaviour of the corroded structures.
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Reliability of maintained ship hulls subjected to corrosion and fatigue under combined loading
Journal of Constructional Steel Research, 1999Co-Authors: C. Guedes Soares, Yordan GarbatovAbstract:A formulation is presented for the assessment of the reliability of longitudinal members of a ship hull as a result of fatigue and corrosion under combined loading. The model allows for the existence of multiple cracks and it accounts for the crack growth process. The time dependent degrading effect of corrosion and crack growth on the midship section modulus are modelled as random processes. The reliability is predicted by a time variant formulation and, using a two-failure criterion, the effects of maintenance actions in increasing the reliability are shown. The sensitivity of the reliability estimates with respect to different loading combinations is also studied. The formulation has been applied to a tanker.
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Fatigue reliability of the ship hull girder
Marine Structures, 1996Co-Authors: C. Guedes Soares, Yordan GarbatovAbstract:A formulation is presented for the assessment of the reliability of a ship hull with respect to fatigue failure of the longitudinal members. The model allows for the existence of multiple cracks both in the stiffeners and in the plating and it models the crack growth process. The effect of the cracks in decreasing the midship section modulus is quantified as a function of time and the resulting reliability is quantified. The sensitivity of the reliability estimates with respect to several parameters is also studied. Keywords:
Sung-chul Shin - One of the best experts on this subject based on the ideXlab platform.
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FSKD (2) - Feature recognition technique from 2d ship drawings using fuzzy inference system
Fuzzy Systems and Knowledge Discovery, 2005Co-Authors: Sung-chul ShinAbstract:This paper presents the feature recognition technique that recognizes the features from 2D ship drawings using the fuzzy inference system. Generally, ship drawings include a lot of symbols and texts. They were complicatedly combined each other. So, it is very difficult to recognize the feature from 2D ship model. The fuzzy inference system is suitable to solve these problems. Input information for fuzzy inference is connection type of drawing elements and properties of element. Output value is the correspondence between target feature and candidate feature. The recognition rule is the fuzzy rule that has been predefined by designer. In this study, the midship section drawing of general cargo ship was used to verifying suggested methodology. Experimental results showed that this approach is more efficient than existing methods and reflects the human knowledge for recognition of the feature.
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feature recognition technique from 2d ship drawings using fuzzy inference system
Fuzzy Systems and Knowledge Discovery, 2005Co-Authors: Sung-chul ShinAbstract:This paper presents the feature recognition technique that recognizes the features from 2D ship drawings using the fuzzy inference system. Generally, ship drawings include a lot of symbols and texts. They were complicatedly combined each other. So, it is very difficult to recognize the feature from 2D ship model. The fuzzy inference system is suitable to solve these problems. Input information for fuzzy inference is connection type of drawing elements and properties of element. Output value is the correspondence between target feature and candidate feature. The recognition rule is the fuzzy rule that has been predefined by designer. In this study, the midship section drawing of general cargo ship was used to verifying suggested methodology. Experimental results showed that this approach is more efficient than existing methods and reflects the human knowledge for recognition of the feature.
S. Saad-eldeen - One of the best experts on this subject based on the ideXlab platform.
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Experimental strength assessment of thin steel plates with a central elongated circular opening
Journal of Constructional Steel Research, 2016Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract This work assesses the ultimate strength of experimentally tested steel plates with a large central elongated circular opening, subjected to uni-axial compressive load. A series of experimental tests have been carried out on plates that were part of a real structure, which represents a scaled midship section of single hull tanker ship, tested in a corrosive environment in direct contact with seawater. One elongated circular opening shape with different sizes is analyzed and the effect of the opening size on the ultimate strength is investigated. The force–displacements relationships are presented and the dissipated energy is analyzed. Stress–strain relationships, resilience and toughness have been evaluated. The collapse modes are discussed and the ultimate strength has been compared with recently published studies showing a good agreement in the trend.
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Experimental assessment of the ultimate strength of a box girder subjected to severe corrosion
Marine Structures, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract The objective of this paper is to describe the experimental assessment of the ultimate strength of a severely corroded box girder subjected to a uniform bending moment resulting from four-point loading. Three box girders that could simulate the behaviour of midship sections have been deteriorated in corrosive seawater environment to simulate different levels of corrosion degradation of ageing ship structures. During the deterioration process, various parameters have been controlled and the total weight lost was registered. Corroded plate thicknesses have been measured in 212 points and a statistical analysis has been performed. The resulting corrosion wastage has been fitted by a non-linear time variant degradation model. The experimental results of the ultimate strength test of a severely corroded box girder subjected to a four-point loading have been analysed. The load-displacement and moment-curvature relationship is discussed, different failure modes are identified, and the strain gauges readings are analysed.
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Compressive strength assessment of a moderately corroded box girder
Marine Systems & Ocean Technology, 2011Co-Authors: S. Saad-eldeen, Yordan Garbatov, C. Guedes SoaresAbstract:This paper presents the results of the experimental test of a multispan corroded stiffened box girder subjected to moderate corrosion deterioration. The experiment is carried out to study the compressive collapse strength of a box girder subjected to four-point loading, which results in a constant vertical bending moment. The box girder reproduces the behaviour of a midship hull structure. The collapse modes are discussed, showing the effect of corrosion on the final collapse mode and the release of the residual stresses. The load-displacement, moment-curvature as well as the strain readings are presented and analysed. The ultimate bending moment results have been compared with some existing formulas, showing the lack of the prediction of the behaviour of the corroded structures.