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Guedes C Soares - One of the best experts on this subject based on the ideXlab platform.
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structural reliability analysis of Ship Hulls accounting for collision or grounding damage
Journal of Marine Science and Application, 2020Co-Authors: Branka Bužancic Primorac, Josko Parunov, Guedes C SoaresAbstract:Classical structural reliability analysis of intact Ship Hulls is extended to the case of Ships with collision or grounding damages. Still water load distribution and residual bending moment capacity are included as random variables in the limit state equation. The probability density functions of these random variables are defined based on random damage parameters given by the Marine Environment Protection Committee of the International Maritime Organization, while the proposed reliability formulation is consistent with international recommendations and thus may be valuable in the development of rules for accidental limit states. The methodology is applied on an example of an Aframax oil tanker. The proposed approach captures in a rational way complex interaction of different pertinent variables influencing safety of damaged Ship structure.
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numerical assessment of the structural crashworthiness of corroded Ship Hulls in stranding
Ocean Engineering, 2018Co-Authors: Bin Liu, Yordan Garbatov, Ling Zhu, Guedes C SoaresAbstract:Abstract Corrosion wastage is one of the most important structural degradation phenomena of ageing Ships and leads to severe consequences in reducing the strength of Ship structures in all loading conditions during the service life. This paper investigates the effect of steel corrosion degradation on the Ship structural crashworthiness in grounding numerically, considering the reduction of the thickness of structural components and the loss of material mechanical properties due to corrosion. Corrosion degradation causes the change of material properties, such as Young's modulus, yield stress, ultimate tensile stress and fracture strain, which determine the yielding, work hardening and critical failure strain of the material defined in an impact analysis. The mean values of accident statistics of grounding are considered to define the seabed shape and size. The objective of the paper is to develop a practical engineering assessment of the crashworthiness of ageing Ship structures accounting for the corrosion degradation. The numerical analyses evaluate the reaction force and energy dissipation versus the Ship damage during the grounding accident. The resistance of intact and corroded Ship Hulls is compared shown that, for example, the absorbed energy of the corroded Ship hull decreases 33.8% with a wasted thickness of 2.0 mm in stranding. Also, some discussions are presented on the accuracy of numerical analyses.
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hydrodynamic interaction forces on Ship Hulls equipped with propulsors
Volume 4: Offshore Geotechnics; Ronald W. Yeung Honoring Symposium on Offshore and Ship Hydrodynamics, 2012Co-Authors: Serge Sutulo, Guedes C SoaresAbstract:Typically, study of hydrodynamic interaction between vessels navigating in close proximity to each other is limited to hydrodynamics of bare Hulls. Meanwhile, Ship propulsors, especially heavily loaded, which may happen in accelerating motion, can alter substantially the flow and distribution of pressure on the Hulls which can be viewed as generalization of the thrust deduction phenomenon. The 3D doubled body potential interaction code based on the source panel method developed earlier by the authors has been enhanced to include the effect of a propeller on each of the interacting Ships under the assumption that the propeller jets (slipstreams) are not involved into the interaction. Each propeller is simulated by a disk of sinks further approximated with a polygon composed of identical triangular panels with identical constant sink density linked to the thrust of the propulsor according to the actuator disk theory. Comparative computations were carried out for two identical tanker vessels in the close-proximity overtaking manoeuvre at various values of the loading coefficient of each propeller. The loading coefficient is not supposed to be necessarily defined by the steady propulsion point. Numerical results demonstrate that a heavily loaded propeller substantially modifies the pressure distribution on both Hulls resulting in alteration of the hydrodynamic interaction loads, especially of the surge force and yaw moment.
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free surface flow around Ship Hulls using an interface capturing method
ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering, 2008Co-Authors: C Ciortan, Guedes C Soares, Juan B V WanderleyAbstract:In the present paper, a compressible free surface code is used for simulating the flow around Ship Hulls. The code simulates both turbulent and laminar, free-surface flow around Ship Hulls, using the Slightly Compressible Flow formulation. The runs were performed for a Series60, Cb = 0.6 hull in standard conditions of Froude numbers and the results were compared against experimental and numerical results. The turbulence model used is Baldwin-Lomax. The numerical scheme was marched in time using the 2nd order, explicit Runge-Kutta. For the time being, the code uses a fixed grid on which the kinematic free surface equation is solved. Several boundary conditions were implemented and their behaviour assessed. The results show fair agreement with the experimental results.Copyright © 2008 by ASME
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reliability assessment for ultimate longitudinal strength of Ship Hulls in composite materials
Probabilistic Engineering Mechanics, 2007Co-Authors: Nian-zhong Chen, Guedes C SoaresAbstract:Abstract A method for reliability assessment of the ultimate longitudinal strength of Ship Hulls in composite materials is described. The ultimate longitudinal strength of a Ship hull is predicted by a progressive collapse analysis based on load–average strain curves of stiffened composite panels that are developed by a progressive failure nonlinear finite element analysis. Sagging, hogging and slamming conditions are regarded as three extreme loading conditions and the corresponding limit state functions are established with an appropriate stochastic modeling of the basic design variables, such as the modeling uncertainties, the materials properties, the lamina thickness, the lamination angle, the still-water moment, the wave-induced moment, and the slamming-induced moment. The reliability estimation is achieved by an improved first-order reliability algorithm. The sensitivities of the reliability estimates with respect to model parameters are determined and those parameters with small sensitivity factors are replaced by deterministic values to improve the computational efficiency in the prediction of the ultimate longitudinal strength of Ship hull. An all-composite Ship is analyzed for demonstration.
Nian-zhong Chen - One of the best experts on this subject based on the ideXlab platform.
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The effects of stochastic characteristics of materials on the reliability of a composite Ship hull
Journal of Marine Science and Application, 2011Co-Authors: Wei Zhang, Nian-zhong Chen, Wenyong Tang, Shengkun ZhangAbstract:The effects of stochastic characteristics of materials on the reliability of Ship Hulls made of composite materials under longitudinal moment were extensively studied using reliability and sensitivity calculations of a composite Ship hull which was sagging. The reliability indices and failure probabilities of the Ship in three kinds of failure modes (buckling, material failure, and ultimate collapse) were calculated by the surface response method and JC method. The importance factors of random variables in stochastic models, such as the model errors in predicting the ultimate longitudinal strength of Ship and the longitudinal bending moment that the Ship withstands, as well as the stochastic characteristics of materials in the models used, were calculated. Then, the effects of these random variables, including the stochastic characteristics of materials on the reliability index and the failure probability of Ships which were sagging, were discussed with their importance factors. The results show that the effects of stochastic characteristics of materials on the reliability of Ship Hulls made of composite materials should be considered during the reliability assessment of composite Ships. Finally, some conclusions and recommendations were given for high-speed Ship design and safety assessment.
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Ultimate Longitudinal Strength of Ship Hulls of Composite Materials
Journal of Ship Research, 2008Co-Authors: Nian-zhong Chen, C. Guedes SoaresAbstract:A progressive collapse analysis method is proposed to predict the ultimate longitudinal strength of Ship Hulls of composite materials. The load-average strain curve derived from a progressive failure nonlinear finite element analysis is adopted for representing the behavior of each stiffened composite panel forming a hull cross section. The bending moment of the Ship hull under a prescribed curvature is achieved by integrating the reaction force of each stiffened panel over a hull cross section based on the load-average strain curves. The ultimate longitudinal strength of a Ship hull is obtained from the moment-curvature relationShip of the Ship hull, which is established by imposing progressively increasing curvatures of a hull cross section. An all-composite Ship is analyzed as an application.
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Reliability analysis of Ship Hulls made of composite materials under sagging moments
Journal of Marine Science and Technology, 2007Co-Authors: Nian-zhong Chen, Carlos Guedes SoaresAbstract:An approach is presented to assess the reliability of Ship Hulls made of composite materials under sagging moments. Buckling, first-ply failure, and ultimate collapse are regarded as the three possible failure modes of Ship Hulls of composite materials under sagging moments. Reliability estimates were carried out by a combination of the first-order second-moment method and the response surface methodology. A Ship hull of composite materials under sagging moments was evaluated and the results showed that the effects on reliability estimates of the model uncertainty in the longitudinal strength of the Ship hull, the model uncertainty of the sagging moments, and the sagging moments were significant, whereas the influences of the stochastic characteristics of material elastic moduli were relatively unimportant.
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reliability assessment for ultimate longitudinal strength of Ship Hulls in composite materials
Probabilistic Engineering Mechanics, 2007Co-Authors: Nian-zhong Chen, Guedes C SoaresAbstract:Abstract A method for reliability assessment of the ultimate longitudinal strength of Ship Hulls in composite materials is described. The ultimate longitudinal strength of a Ship hull is predicted by a progressive collapse analysis based on load–average strain curves of stiffened composite panels that are developed by a progressive failure nonlinear finite element analysis. Sagging, hogging and slamming conditions are regarded as three extreme loading conditions and the corresponding limit state functions are established with an appropriate stochastic modeling of the basic design variables, such as the modeling uncertainties, the materials properties, the lamina thickness, the lamination angle, the still-water moment, the wave-induced moment, and the slamming-induced moment. The reliability estimation is achieved by an improved first-order reliability algorithm. The sensitivities of the reliability estimates with respect to model parameters are determined and those parameters with small sensitivity factors are replaced by deterministic values to improve the computational efficiency in the prediction of the ultimate longitudinal strength of Ship hull. An all-composite Ship is analyzed for demonstration.
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longitudinal strength analysis of Ship Hulls of composite materials under sagging moments
Composite Structures, 2007Co-Authors: Nian-zhong Chen, Guedes C SoaresAbstract:An approach to estimate the longitudinal strength of Ship Hulls in composite materials is presented in the paper. Typical Ship configurations have as dominant failure mode the failure of the deck under compression associated with sagging moments. Ship Hulls are modeled as assemblies of stiffened composite panels. Buckling, material failure and ultimate collapse of the stiffened panels are predicted by nonlinear finite element analysis, which is based on a degenerated three-dimensional laminated composite shell element with updated Lagrangian formulation and first-order shear deformable kinematics. According to buckling, material failure and ultimate collapse of stiffened panels, the corresponding longitudinal strengths of Ship hull are derived from a simplified method. A Ship hull under sagging is analysed as an example application.
Carlos Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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Reliability analysis of Ship Hulls made of composite materials under sagging moments
Journal of Marine Science and Technology, 2007Co-Authors: Nian-zhong Chen, Carlos Guedes SoaresAbstract:An approach is presented to assess the reliability of Ship Hulls made of composite materials under sagging moments. Buckling, first-ply failure, and ultimate collapse are regarded as the three possible failure modes of Ship Hulls of composite materials under sagging moments. Reliability estimates were carried out by a combination of the first-order second-moment method and the response surface methodology. A Ship hull of composite materials under sagging moments was evaluated and the results showed that the effects on reliability estimates of the model uncertainty in the longitudinal strength of the Ship hull, the model uncertainty of the sagging moments, and the sagging moments were significant, whereas the influences of the stochastic characteristics of material elastic moduli were relatively unimportant.
C. Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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Reliability of Ship Hulls subjected to corrosion and maintenance
Structural Safety, 2013Co-Authors: Alsayed Zayed, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract The objective of the present study is to analyse the lifetime reliability of Ship hull structures subjected to corrosion degradation, including the effects of inspection and repair actions. Different environmental conditions affecting the corrosion deterioration of Ship hull are considered. The uncertainties in an inspection are accounted for by a probability of detection model that introduces additional probabilistic events at the different inspection times. Ship loading uncertainties are modelled based on the time ratio spent under each loading condition during the Ship's service life. Each time ratio is defined as the probability of encountering its corresponding loading condition. Based on a fast integration technique, an algorithm is developed to assess the structural reliability of Ship Hulls efficiently. Ship loading is only composed of still water and wave induced vertical bending moments. The ultimate vertical bending moment capacity of the Ship hull is considered as a limit state.
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Ultimate Longitudinal Strength of Ship Hulls of Composite Materials
Journal of Ship Research, 2008Co-Authors: Nian-zhong Chen, C. Guedes SoaresAbstract:A progressive collapse analysis method is proposed to predict the ultimate longitudinal strength of Ship Hulls of composite materials. The load-average strain curve derived from a progressive failure nonlinear finite element analysis is adopted for representing the behavior of each stiffened composite panel forming a hull cross section. The bending moment of the Ship hull under a prescribed curvature is achieved by integrating the reaction force of each stiffened panel over a hull cross section based on the load-average strain curves. The ultimate longitudinal strength of a Ship hull is obtained from the moment-curvature relationShip of the Ship hull, which is established by imposing progressively increasing curvatures of a hull cross section. An all-composite Ship is analyzed as an application.
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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.
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Reliability of Maintained Ship Hulls Subjected to Corrosion
Journal of Ship Research, 1996Co-Authors: C. Guedes Soares, Yordan GarbatovAbstract:A time-variant formulation is presented to model 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 showed the effect of plate replacement when its thickness reached 75% of the original thickness. The example results also illustrated 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 and allowable stresses.
Kaj Riska - One of the best experts on this subject based on the ideXlab platform.
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a generalized probabilistic model of ice load peaks on Ship Hulls in broken ice fields
Cold Regions Science and Technology, 2014Co-Authors: Abdillah Suyuthi, Bernt J. Leira, Kaj RiskaAbstract:Abstract On some occasions, especially when traveling in a broken ice field, the process of ice induced loads on Ship Hulls cannot be well modeled by traditional statistical models which are usually applied for this purpose. Examples of such are the one-parameter exponential and the Weibull's models. The fitting achieved by application of these models could generally result in underestimation of the predicted extreme values. Therefore a so-called generalized model, i.e. the three-parameter exponential model, is proposed in order to improve the process of fitting. The proposed model is actually a proportional combination of two one-parameter exponential models. It tends to give more conservative predicted extreme values as compared to the one-parameter exponential and the Weibull's models. Various approaches for estimation of the parameters are treated, i.e. the method of moments, the non-linear least square method, the non-linear least square method based on application of Kernel density estimation, and the maximum likelihood estimators. The fitting by means of the non-linear least square method was observed to give the best results. However, more stable predictions are provided by the maximum likelihood estimators.
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Fatigue damage of Ship Hulls due to local ice-induced stresses
Applied Ocean Research, 2013Co-Authors: Abdillah Suyuthi, Bernt J. Leira, Kaj RiskaAbstract:Abstract Fatigue damage in a Ship hull could lead to leakage of ballast or cargo, water intrusion, degradation of hull strength, or even worse, i.e. catastrophic structural failure. For Ships navigating in ice-covered waters, fatigue damage due to ice actions can be of importance. The present paper proposes a systematic procedure for fatigue damage assessment in relation to Ships navigating in ice-covered waters. Closed form expressions for the fatigue damage based on the Palmgren–Miner’s rule are derived for several different statistical models of the stress amplitudes, i.e. the exponential, the Weibull’s, and the three-parameter exponential distributions. Additional expressions are also provided when stress concentration factor and/or a lower threshold of the stress amplitude are taken into account. The proposed procedure for fatigue damage assessment reflects the variation in ice conditions, vessel’s speed, and operational modes. Some practical concerns related to application of the proposed procedure are also discussed. A particular example of fatigue damage calculation is presented, where data obtained from full scale measurement performed on board of the vessel KV Svalbard in the winter 2007 are utilized.
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statistics of local ice load peaks on Ship Hulls
Structural Safety, 2013Co-Authors: Abdillah Suyuthi, Bernt J. Leira, Kaj RiskaAbstract:Abstract This paper focuses on statistical inference in relation to the peak process of local ice loading on Ship Hulls. Such inference comprises selection of a statistical model (by means of P–P plot, Q–Q plot, and probability paper), parameter estimation (by means of LSM, MoM, and MLE), evaluation of the confidence interval of the estimators, and goodness-of-fit testing of the initial distribution. Several different approaches are considered for each of the steps and numerical experiments were performed in order to reaffirm suggestions from previous works and extend the analysis. A particular data set provided by full scale measurements on the coast guard vessel KV Svalbard during the Winter 2007 was analyzed by means of the present approach. Four probability models were tested and the best fit to the data was provided by the Weibull distribution with the shape parameter being located in the range 0.7
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short term extreme statistics of local ice loads on Ship Hulls
Cold Regions Science and Technology, 2012Co-Authors: Abdillah Suyuthi, Bernt J. Leira, Kaj RiskaAbstract:Abstract This paper focuses on prediction of short term extreme values of local ice loads on Ship Hulls. The analysis is based on the exact classical method, which utilizes the selected statistical models as its initial distribution. A conventional approach, where the number of events is considered as a fixed value, i.e. equal to the expected number of events for a given duration, is employed. An alternative approach, which accommodates the number of ice load peak events as a random variable, is also investigated. An asymptotic approach, which is based on the one-minute maxima, is also investigated. When compared with the other two methods, the asymptotic approach tends to give similar level of extreme values.
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non parametric probabilistic approach of ice load peaks on Ship Hulls
Volume 6: Materials Technology; Polar and Arctic Sciences and Technology; Petroleum Technology Symposium, 2012Co-Authors: Abdillah Suyuthi, Bernt J. Leira, Kaj RiskaAbstract:Due to its complex phenomenon, ice-induced load process could not be physically possible to be modeled by a specific well established probabilistic model. Therefore, a non parametric approximate probabilistic approach should be performed based on the available data. This paper describes the procedure and also the extrapolation to get the short term and long term extreme values. Comparison with the classical approach, where the initial distribution of ice-induced load is assumed to be one of the well established probabilistic models, was made. The comparisons discussed in this paper were explored by using the same available data of full scale measurement on board a coastal guard vessel KV Svalbard during the winter 2007. There was a tendency that the non parametric approach produces more conservative results.Copyright © 2012 by ASME
