Wave induced extreme hull girder loads on containerships

2008 ◽  
Author(s):  
J. Juncher Jensen ◽  
Preben Terndrup Pedersen ◽  
Bill Shi ◽  
Sue Wang ◽  
Martin Petricic ◽  
...  
Keyword(s):  
Bending Moments ◽  
Wave Load ◽  
Spreadsheet Program ◽  
Hull Girder ◽  
Conceptual Design Phase ◽  
Strip Theory ◽  
Bow Flare ◽  
Analytical Formulas ◽  
Approximate Wave ◽  
Wave Induced

This paper provides simple but rational procedures for prediction of extreme wave – induced sectional hull girder forces with reasonable engineering accuracy. The procedures take into account main ship hull characteristics such as: length, breadth, draught, block coefficient, bow flare coefficient, forward speed and hull flexibility. The vertical hull girder loads are evaluated for specific operational profiles. Firstly a quadratic strip theory is presented which can give separate predictions for the hogging and sagging bending moments and shear forces and for hull girder loads. Then this procedure is used as a base to derive semi-analytical formulas such that approximate wave load calculations can be performed by a simple spreadsheet program. Due to the few input parameters this procedure can be used to estimate the wave-induced bending moments at the conceptual design phase. Since the procedure is based on rational methods it can be applied for novel single hull ship types not presently covered by the rules of the classification societies or to account for specific operational profiles.

Estimation of hull girder vertical bending moments including non-linear and flexibility effects using closed form expressions

2009 ◽  
Vol 223 (3) ◽  
pp. 377-390 ◽  
Author(s):  
P T Pedersen ◽  
J J Jensen
Keyword(s):  
Closed Form ◽  
Linear Response ◽  
Bending Moment ◽  
Phase Lag ◽  
Bending Moments ◽  
Hull Girder ◽  
Strip Theory ◽  
Non Linear ◽  
Bow Flare ◽  
Wave Induced

A simple but rational procedure for prediction of extreme wave-induced hull girder bending moment in slender mono-hull displacement vessels is presented. The procedure takes into account main ship hull characteristics such as length, breadth, draught, block coefficient, bow flare coefficient, forward speed, and hull flexibility. The wave-induced loads are evaluated for specific operational profiles. Non-linearity in the wave bending moment is modelled using results derived from a second-order strip theory and water entry solutions for wedge-type sections. Hence, bow flare slamming is accounted for through a momentum type of approach. The stochastic properties of this non-linear response are calculated through a monotonic Hermite transformation. In addition, the impulse loading attributable to, for example, bottom slamming or a rapid change in bow flare is included using a modal expansion in the two lowest vertical vibration modes. These whipping vibrations are added to the wave frequency non-linear response, taking into account the rise time of the impulse response as well as the phase lag between the occurrence of the maximum non-linear load and the maximum impulse load. Previous results for the sagging bending moment are validated by comparison with fully non-linear strip theory calculations and supplemented with new closed form results for the hogging bending moment. Focus is on the extreme hull girder hogging bending moment. Owing to the few input parameters, this procedure can be used to estimate the wave-induced bending moments at the conceptual design phase. Another application area is for novel single-hull ship types not presently covered by the rules of the classification societies. As one application example the container ship MSC Napoli is considered. Further validations are needed, however, in order to select proper values of the parameters entering the analytical form of the slamming impulse.

Bending Moments and Shear Forces in Ships Sailing in Irregular Waves

1981 ◽  
Vol 25 (04) ◽  
pp. 243-251
Author(s):  
J. Juncher Jensen ◽  
P. Terndrup Pedersen
Keyword(s):  
Linear Part ◽  
Vertical Motion ◽  
Bending Moment ◽  
Irregular Waves ◽  
Bending Moments ◽  
Shear Forces ◽  
Strip Theory ◽  
Wave Heights ◽  
Exciting Forces ◽  
Wave Induced

This paper presents some results concerning the vertical response of two different ships sailing in regular and irregular waves. One ship is a containership with a relatively small block coefficient and with some bow flare while the other ship is a tanker with a large block coefficient. The wave-induced loads are calculated using a second-order strip theory, derived by a perturbational procedure in which the linear part is identical to the usual strip theory. The additional quadratic terms are determined by taking into account the nonlinearities of the exiting waves, the nonvertical sides of the ship, and, finally, the variations of the hydrodynamic forces during the vertical motion of the ship. The flexibility of the hull is also taken into account. The numerical results show that for the containership a substantial increase in bending moments and shear forces is caused by the quadratic terms. The results also show that for both ships the effect of the hull flexibility (springing) is a fair increase of the variance of the wave-induced midship bending moment. For the tanker the springing is due mainly to exciting forces which are linear with respect to wave heights whereas for the containership the nonlinear exciting forces are of importance.

An Uncertainty Evaluation of Different Fidelity Methods to Predict Ship Motions and Structural Loading in Waves

2020 ◽  
Author(s):  
Nicholas Husser ◽  
Stefano Brizzolara
Keyword(s):  
Experimental Data ◽  
Wave Length ◽  
Panel Method ◽  
Ship Motions ◽  
Bending Moments ◽  
Wave Load ◽  
Strip Theory ◽  
Linear Effects ◽  
Structural Loading ◽  
Extensive Experimental Data

Abstract In this study, four approaches are investigated to predict the motions and structural loads on a containership in waves. The Flockstra (1974) containership model is used as the benchmark for this study as extensive experimental data is available to compare to the predictions. The hydrodynamic loads and motions are predicted using strip theory, a zero speed Green’s functions panel method with forward speed correction, a fully unsteady 3D panel method and unsteady RANSE simulations for limited cases. Simulations are performed at Fn = 0.245 in head, stern quartering, and bow quartering seas for wave length to ship length ration λ/L of 0.35–1.40. The accuracy of each method, relative to experimental results, in predicting the amplitudes of heave, pitch, and roll are investigated. Vertical and horizontal bending moments, shear forces, and the torsional moment on the hull at midships and 0.25LBP forward and aft of midships are also calculated and compared with the measured values. Through comparison with experimental data, the relative uncertainty of all four methodologies in predicting both motions and structural loads are assessed and discussed. Overall, all linearized potential flow methods show a large discrepancy with the experimental loads, motivating the need for further studies on non-linear effects for this particular ship type. This paper has been prepared in the framework of the ISSC-ITTC special joint committee on uncertainty quantification in wave load estimation.

Effects of Avoidance of Heavy Weather on the Wave Induced Load on Ships

2006 ◽  
Author(s):  
Zhi Shu ◽  
Torgeir Moan
Keyword(s):  
Green Water ◽  
Vertical Acceleration ◽  
Sea State ◽  
Hull Girder ◽  
Term Prediction ◽  
Strip Theory ◽  
Operational Criteria ◽  
Wave Induced ◽  
Long Term Prediction

This paper is concerned with evaluating the effect of avoidance of heavy weather on the long term wave induced loads on ships. Two hydrodynamic codes VERES based on a 2D strip theory and WASIM based on a 3D Rankine panel method are employed to calculate the wave induced loads and motions on various vessels. Two models for heavy weather avoidance are proposed. The first is based upon the assumption that operational criteria relevant to vertical acceleration, green water and bottom slamming are fulfilled. The second one is based upon the assumption that the sea state forecasts are available to the ship master, and that rerouting is made. And based on the first model considering avoidance of heavy weather and the hydrodynamics results calculated from two codes, the wave induced hull girder loads are obtained. The results are discussed. In particular, the effect of different hydrodynamic codes and various scatter diagrams are assessed. After all, the long term prediction of wave induced hull girder loads considering the effect of avoidance of heavy weather will give a relatively more realistic evaluation of the extreme hull girder loads. Finally the results from ship rules will also be re-evaluated compared with the long term prediction with and without heavy weather avoidance.

Assessment of the Total Ship’s Hull Girder Bending Stresses When Unified Model of Sagging and Hogging Bending Moments is Used

2009 ◽  
Author(s):  
Lyuben D. Ivanov
Keyword(s):  
Life Span ◽  
Bending Moment ◽  
Extreme Value Statistics ◽  
Bending Moments ◽  
Hull Girder ◽  
Section Modulus ◽  
Probabilistic Distribution ◽  
Bending Stresses ◽  
Distribution Laws ◽  
Wave Induced

A method is proposed for calculating the hull girder bending stresses following the procedure in the class rules but in probabilistic terms, i.e. the still water and the wave-induced bending moments; the total hull girder bending moment; the hull girder section modulus and the hull girder bending stresses are treated as random variables with corresponding probabilistic distributions. The still water and wave-induced hull girder hogging and sagging loads are presented in probabilistic format as one phenomenon, i.e. using bi-modal probability density functions. The probabilistic distribution of the total hull girder load is calculated using the rules of the composition of the distribution laws of the constituent variables. After that, the hull girder geometric properties are presented in probabilistic format as annual distributions and distributions for any given life-span. Thus, it becomes possible to calculate both the annual probabilistic distributions and the probabilistic distribution for any given ship’s life span of the hull girder stresses. Individual amplitudes statistical analysis and extreme value statistics are used. Then, the probability of exceeding the permissible hull girder bending stresses in the class rules is calculated. An example is given for 25K DWT bulk carrier.

Effect of the nonlinear vertical wave-induced bending moments on the ship hull girder reliability

2016 ◽  
Vol 119 ◽  
pp. 193-207 ◽  
Author(s):  
B. Gaspar ◽  
A.P. Teixeira ◽  
C. Guedes Soares
Keyword(s):  
Ship Hull ◽  
Bending Moments ◽  
Hull Girder ◽  
Wave Induced

Symmetric Response of a Hydroelastic Scaled Container Ship Model in Regular and Irregular Waves

2014 ◽  
Author(s):  
Sheng Peng ◽  
Pandeli Temarel ◽  
S. S. Bennett ◽  
Weiguo Wu ◽  
Zhengguo Liu ◽  
...  
Keyword(s):  
Full Scale ◽  
Irregular Waves ◽  
Container Ship ◽  
Bending Moments ◽  
Segmented Model ◽  
Numerical Predictions ◽  
Hull Structure ◽  
Strip Theory ◽  
Head Waves ◽  
Wave Induced

Wave-induced vibrations, such as whipping and springing, of container carriers have been attracting much attention because of their effects on hull-girder bending moments and fatigue damage. An investigation has been carried out comparing experimental measurements and numerical predictions of symmetric wave-induced loads (i.e. vertical bending moment) of the latest River-sea link container ship design, LPP = 130 m. The dual mission characteristics, namely rivers and open seas, make this type of ship an extremely interesting type of container carrier, particularly in terms of springing and whipping. A backbone beam segmented model is used in the experiments with the focus on springing- and whipping-induced vertical bending moments, for the model travelling at Fn = 0.21 in regular and long-crested irregular head waves, of 2.5m full-scale height or significant wave height. In addition higher order (harmonics) vertical bending moments (VBM) are also extracted from the experiments. The measurements are taken at amidships and the fore and aft quarters. Numerical predictions, for both the full-scale vessel and segmented model, are obtained using the two-dimensional linear hydroelasticity theories, where the hull structure is idealized as a non-uniform beam and the fluid actions evaluated using strip theory. The measured model test results, in relatively moderate conditions based on a particular area of operation for this low-draught vessel, indicate that nonlinear springing accounts for a significant portion of the total wave-induced bending moments in regular and, to an extent, irregular waves and slamming effects are small due to the operational area selected. The numerical predictions in regular waves show that linear hydroelasticity analysis can only predict similar trends in the variation of the VBM and the resonance peak. On the other hand, in long crested irregular waves the linear hydroelasticity analysis provides peak statistics that are commensurate with the measurements. The numerical predictions were obtained for two variants, having L = LPP and L = 0.9 LPP, the latter corresponding to the length of the backbone.

Time-Variant Reliability Assessment of FPSO Considering Corrosion and Collision

2006 ◽  
Author(s):  
Daokun Zhang ◽  
Wenyong Tang ◽  
Shengkun Zhang
Keyword(s):  
Oil And Gas ◽  
Bending Moment ◽  
Bending Moments ◽  
Hull Girder ◽  
Corrosion Defect ◽  
Direct Damage ◽  
Collision Condition ◽  
Inspection And Maintenance ◽  
Offshore Oil And Gas ◽  
Wave Induced

Floating production, storage, and offloading (FPSO) system has been widely used in the offshore oil and gas exploitations. Since it has long intervals of docking for thorough inspection and maintenance, and is exposed to collision risk at sea, the time-variant reliability of FPSO becomes very important as for the risks of corrosion and collision. The corrosion defect is modeled as the exponential function of time. The Idealized Structural Unit Method is also proposed to predict ultimate strength of hull girder. Still water and wave-induced bending moments are also combined into stochastic processes. Reliabilities of intact hull during the service are calculated as references to those of collided hulls with effect of corrosion defect. Collision condition is a focus in this paper, where collided hulls are modeled according to ABS instructions. According to the instructions, the section with highest bending moment, which almost locates at the mid ship, should be noticed. Therefore still water bending moments of mid section of collided hulls are achieved and divided into two groups based on collision positions. One is that the mid section is broken, which is named as “direct damage”. Another is that other else section is broken, which is named as “influence”. Result shows that “influence” condition has higher still water bending moment than “direct damage”, which is usually neglected in previous researches. Finally, reliabilities of collided hulls throughout the service life are obtained, which can become references to further inspection and maintenance plan.

Effects of Avoidance of Heavy Weather on the Wave-Induced Load on Ships

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Zhi Shu ◽  
Torgeir Moan
Keyword(s):  
Green Water ◽  
Vertical Acceleration ◽  
Sea State ◽  
Hydrodynamic Analysis ◽  
Hull Girder ◽  
Rankine Panel Method ◽  
Strip Theory ◽  
Operational Criteria ◽  
Wave Induced

This paper is concerned with evaluating the effect of heavy weather avoidance on the long-term wave-induced loads on ships. Two hydrodynamic codes, VERES based on a 2D strip theory and WASIM based on a 3D Rankine panel method, are employed to calculate the wave-induced loads and motions on various vessels. Two models for heavy weather avoidance are envisaged. The first one is based on the assumption that operational criteria relevant to vertical acceleration, green water, and bottom slamming are fulfilled. The second one is based on the assumption that the sea state forecasts are available to the shipmaster and that rerouting is made. Based on the first model, the effect of the heavy weather avoidance on the long-term wave-induced hull girder loads is evaluated. In particular, the effect of hydrodynamic analysis methods and wave scatter diagram are also assessed. The calculated values are compared with those given in ship rules. The results show that several factors should be critically assessed in evaluating the accuracy of the ship rule values.

Efficient and Simplified Time Domain Simulation of Nonlinear Responses of Ships in Waves

2003 ◽  
Vol 47 (03) ◽  
pp. 262-273
Author(s):  
XueKang Gu ◽  
JinWei Shen ◽  
Torgeir Moan
Keyword(s):  
Model Test ◽  
Time Domain ◽  
High Efficiency ◽  
Coupling Effect ◽  
Irregular Waves ◽  
Green Water ◽  
Bending Moments ◽  
Strip Theory ◽  
Bow Flare ◽  
Theoretical Results

In this paper, a nonlinear time-domain strip theory is developed to predict nonlinear vertical ship motions and structural responses in severe waves. The effects of bottom impact, bow flare slamming, and green water on bending moments have been simulated. The flexible modes of the ship hull girder are accounted for by a Timoshenko beam theory. To validate the predicted responses, a model test was conducted for a ship with large bow flare and low bending rigidity, in both regular and irregular waves. The agreements between the calculated results and the model test are fairly good. The coupling effect between higher-order harmonic and the whipping components of vertical bending moments are verified by numerical calculations. Comparative studies with test and other theoretical results are also carried out for an S-175 containership with two kinds of bow flare forms. The causes of whipping and the variance in theoretical results are discussed. The good performance and high efficiency will make it possible to use the theory and its code for direct calculation of nonlinear bending moments in a long-term period and to develop a rule formula of design wave loads in the future.

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