A Segmented Model Test of a Container Ship in Head Seas

2017 ◽  
Author(s):  
Brandon M. Taravella ◽  
Kyle E. Marlantes
Keyword(s):  
Computer Program ◽  
Experimental Studies ◽  
Bending Moment ◽  
Order Effect ◽  
Linear Quadratic ◽  
Segmented Model ◽  
Hull Girder ◽  
Strip Theory ◽  
Significant Length ◽  
The University

Dynamic global hull girder response is an important part of the structural design of a ship, especially one with significant length and bow flare. Experimental studies were conducted at the University of New Orleans’ towing tank where a segmented model of a containership was tested in head seas and zero speed. Bending strain at 3 locations along the model’s hull was measured. The results showed peak sagging bending moment that is approximately 25% larger than the peak hogging bending moment at midship. Minor differences were found between positive heave amplitude and negative heave peaks. The results of the experiment were also compared to an “in-house” non-linear quadratic strip theory computer program. The experimental results compared quite well with the numerical results. The results of the experiments and computer program indicate that the dynamic bending moment response is predominantly a second-order effect and linear predictions are not sufficient.

On the Effect of Hull Girder Flexibility on the Vertical Wave Bending Moment for Ultra Large Container Vessels

2012 ◽  
Author(s):  
Ingrid Marie Vincent Andersen ◽  
Jørgen Juncher Jensen
Keyword(s):  
Bending Moment ◽  
Main Concern ◽  
Hull Girder ◽  
Numerical Predictions ◽  
Strip Theory ◽  
Reliability Method ◽  
Non Linear ◽  
Large Container ◽  
The Waves ◽  
Good Agreement

Currently, a number of very large container ships are being built and more are on order, and some concerns have been expressed about the importance of the reduced hull girder stiffness to the wave-induced loads. The main concern is related to the fatigue life, but also a possible increase in the global hull girder loads as consequence of the increased hull flexibility must be considered. This is especially so as the rules of the classification societies do not explicitly account for the effect of hull flexibility on the global loads. In the present paper an analysis has been carried out for the 9,400 TEU container ship used as case-ship in the EU project TULCS (Tools for Ultra Large Container Ships). A non-linear time-domain strip theory is used for the hydrodynamic analysis of the vertical bending moment amidships in sagging and hogging conditions for a flexible and a rigid modelling of the ship. The theory takes into account non-linear radiation forces (memory effects) through the use of a set of higher order differential equations. The non-linear hydrostatic restoring forces and non-linear Froude-Krylov forces are determined accurately at the instantaneous position of the ship in the waves. Slamming forces are determined by a standard momentum formulation. The hull flexibility is modelled as a non-prismatic Timoshenko beam. Generally, good agreement with experimental results and more accurate numerical predictions has previously been obtained in a number of studies. The statistical analysis is done using the First Order Reliability Method (FORM) supplemented with Monte Carlo simulations. Furthermore, strip-theory calculations are compared to model tests in regular waves of different wave lengths using a segmented, flexible model of the case-ship and good agreement is obtained for the longest of the waves. For the shorter waves the agreement is less good. The discrepancy in the amplitudes of the bending moment can most probably be explained by an underestimation on the effect of momentum slamming in the strip-theory applied.

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.

A Method for Designing the Backbone for the Segmented Model of an Ultra-Large Container Carrier

2019 ◽  
Author(s):  
Hui Li ◽  
Jian Zou ◽  
Weijia Sheng ◽  
Xuecong Hu ◽  
Wenjia Hu
Keyword(s):  
Experimental Studies ◽  
Complex Form ◽  
Bending Moment ◽  
Torsional Stiffness ◽  
Mode Shapes ◽  
Wave Loads ◽  
Torsional Moment ◽  
Wave Load ◽  
Segmented Model ◽  
Vertical Bending Moment

Abstract The segmented model test is often used to study the wave load characteristics of large ships as it can account for the hydroealstic effect. The vertical bending moment (VBM) is of crucial importance in ensuring the safety of ocean-going vessels in rough seas, and there exists in the literature a large number of experimental studies of the VBM. For ships with large openings in the deck, for instance, container ships, the lateral wave loads, such as horizontal bending moment (HBM) and torsional moment (TM) in quartering seas, are as important as VBM. There are, however, few studies on the measurement of the coupled horizontal-torsional vibrations of such ships in model tests. In the paper, a method is proposed for designing flexible backbone models that satisfy the similarities of vertical and horizontal bending stiffness as well as the torsional stiffness, and the measurement of the wave load components is also described. In order to meet the similarity of the hull girder stiffness, the backbone cross-section of a complex form is designed. Finite element method (FEM) is used to calculate the natural frequencies and mode shapes of the segmented model. Measurement of the vertical bending moment, horizontal bending moment and torsional moment are calibrated by applying various combinations of loads.

scholarly journals Analytical Method for Geometric Nonlinear Problems Based on Offshore Derricks

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 610
Author(s):  
Chunbao Li ◽  
Hui Cao ◽  
Mengxin Han ◽  
Pengju Qin ◽  
Xiaohui Liu
Keyword(s):  
Analytical Method ◽  
Bending Moment ◽  
Nonlinear Problems ◽  
Weather Conditions ◽  
Order Effect ◽  
Practical Calculation ◽  
Geometrically Nonlinear ◽  
Uniform Load ◽  
Safety Research ◽  
Calculation Results

The marine derrick sometimes operates under extreme weather conditions, especially wind; therefore, the buckling analysis of the components in the derrick is one of the critical contents of engineering safety research. This paper aimed to study the local stability of marine derrick and propose an analytical method for geometrically nonlinear problems. The rod in the derrick is simplified as a compression rod with simply supported ends, which is subjected to transverse uniform load. Considering the second-order effect, the differential equations were used to establish the deflection, rotation angle, and bending moment equations of the derrick rod under the lateral uniform load. This method was defined as a geometrically nonlinear analytical method. Moreover, the deflection deformation and stability of the derrick members were analyzed, and the practical calculation formula was obtained. The Ansys analysis results were compared with the calculation results in this paper.

scholarly journals Effect of Slam Force Duration on the Vibratory Response of a Lightweight High-Speed Wave-Piercing Catamaran

2015 ◽  
Vol 59 (02) ◽  
pp. 69-84
Author(s):  
Jason John McVicar ◽  
Jason Lavroff ◽  
Michael Richard Davis ◽  
Giles Thomas
Keyword(s):  
High Speed ◽  
Bending Strength ◽  
Experimental Studies ◽  
Bending Moment ◽  
Higher Order ◽  
Acute Angle ◽  
Beam Model ◽  
Higher Order Modes ◽  
Hull Structure ◽  
Vertical Bending Moment

When the surface of a ship meets the water surface at an acute angle with a high relative velocity, significant short-duration forces can act on the hull plating. Such an event is referred to as a slam. Slam loads imparted on ships are generally considered to be of an impulsive nature. As such, slam loads induce vibration in the global hull structure that has implications for both hull girder bending strength and fatigue life of a vessel. A modal method is often used for structural analysis whereby higher order modes are neglected to reduce computational effort. The effect of the slam load temporal distribution on the whipping response and vertical bending moment are investigated here by using a continuous beam model with application to a 112 m INCAT wave-piercing catamaran and correlation to full-scale and model-scale experimental data. Experimental studies have indicated that the vertical bending moment is dominated by the fundamental longitudinal bending mode of the structure. However, it is shown here that although the fundamental mode is dominant in the global structural response, the higher order modes play a significant role in the early stages of the response and may not be readily identifiable if measurements are not taken sufficiently close to the slam location. A relationship between the slam duration and the relative modal response magnitudes is found, which is useful in determining the appropriate truncation of a modal solution.

scholarly journals Study on the horizontal bearing characteristics of pile foundation in coral sand

2021 ◽  
Author(s):  
Chunyan Wang ◽  
Hanlong Liu ◽  
Xuanming Ding ◽  
Chenglong Wang ◽  
Qiang Ou
Keyword(s):  
Lateral Displacement ◽  
Experimental Studies ◽  
Deformation Characteristic ◽  
Bending Moment ◽  
Silica Sand ◽  
Pile Head ◽  
Pile Diameter ◽  
Coral Sand ◽  
Horizontal Pressure ◽  
Different Diameters

This paper presents the horizontal bearing characteristics of piles in coral sand and silica sand from comparative experimental studies. A total of 6 model piles with different diameters are tested. The horizontal bearing capacity, deformation characteristic, bending moment, p-y curve, the change in soil horizontal pressure, as well as the particle breakage behaviour of coral sand are investigated. The results show that, in coral sand foundation, the horizontal bearing capacities of piles and the increments of soil horizontal pressures are obviously greater than those in silica sand. Accordingly, the lateral displacement, the rotation of pile head, the bending moment and the corresponding distribution depth in coral sand are significantly smaller than that in silica sand. The p-y curves indicate that the horizontal stiffness of coral sand is greater than that of silica sand. Remarkably, the breakage behaviour of coral sand is mainly distributed in the range of 10 times pile diameter depth and 5 times pile diameter width on the side where the sand is squeezed by pile. Furthermore, in coral sand, the influence of pile size is more pronounced, the squeezing force generated by pile spread farther and its influence range is larger compared to those in silica sand.

scholarly journals The implementation of smartphones in the instructional process in the views of the female students at Hail University

2021 ◽  
Vol 8 (11) ◽  
pp. 30-36
Author(s):  
Laila Mohamed Sedky Genedy ◽  
Keyword(s):  
Standard Deviation ◽  
Learning Process ◽  
Experimental Studies ◽  
Female Students ◽  
Educational Process ◽  
Survey Method ◽  
Arithmetic Average ◽  
Instructional Process ◽  
The University ◽  
Descriptive Survey

This study aims to examine the implications of implementing smartphones in the educational process in the views of students at the University of Hail. The descriptive survey method was used in the research. To achieve the goal of the research, a questionnaire was prepared regarding the degree of use of smartphones in the learning process which is consisted of 20 paragraphs. The research sample was the female students at the University of Hail. It is found that the overall degree is medium as the arithmetic average is 3.34 with a standard deviation of 0.28. It was concluded that students are prodigiously interested in reviewing the university sites. Moreover, it was found that students are immensely skilled in using smartphones for the exchange of electronic messages and the exchange of information. However, they are less interested in submitting electronic assignments. Few students are watching educational presentations on smartphones because of their small size screens and high drainage from the batteries. Therefore, it is highly recommended to conduct experimental studies showing the importance of using the smartphone.

Ship Operational and Safety Aspects of Ballast Water Exchange at Sea

1994 ◽  
Vol 31 (04) ◽  
pp. 315-326
Author(s):  
John B. Woodward ◽  
Michael G. Parsons ◽  
Armin W. Troesch
Keyword(s):  
Bending Moment ◽  
Bending Moments ◽  
University Of Michigan ◽  
Bulk Carrier ◽  
Rough Water ◽  
Design Values ◽  
Wave Heights ◽  
Ballast Tanks ◽  
The University ◽  
Wave Induced

A dry bulk carrier, a tanker, and a containership—taken as typical of ships trading to U.S. ports—are analyzed for possible hazards caused by emptying and refilling ballast tanks at sea. Using hydrostatic data furnished by the shipowners, hull bending moments and stabilities are investigated to find the tank-emptying operations that produce the greatest changes in those parameters. As should be expected, bending moment changes do not exceed allowable stillwater values. Changes in GM are insignificant. The worst hydrostatic cases serve as a guide to conditions that should be analyzed in rough water. The University of Michigan SHIPMO program shows that in waves of 10-ft significant height wave-induced bending moments and shears are far below the design values published by the American Bureau of Shipping. On the other hand, in waves of 20-ft significant height, the maximum wave heights that occur occasionally can cause moments or shears that exceed design values. For the 20-ft case, both linear and nonlinear versions of SHIPMO are used.

Hull-Girder Reliability of a Chemical Tanker

2009 ◽  
Vol 46 (04) ◽  
pp. 192-199
Author(s):  
Jôsko Parunov ◽  
Maro Corak ◽  
C. Guedes Soares
Keyword(s):  
International Association ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Reliability Method ◽  
Reliability Bound ◽  
Oil Tanker

The aim of the paper is to calculate hull-girder reliability of chemical tanker according to the reliability model proposed by International Maritime Organization (IMO). The probability of hull-girder failure is calculated using a first-order reliability method for two operational profiles—one typical for oil tanker and the other one modified in order to reflect differences between oil tanker and chemical tanker. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with International Association of Classification Societies (IACS) recommended procedure. The stillwater loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by single-step procedure. The reliability analysis is performed for "as-built" ship and for "corroded" ship according to corrosion deduction thickness from new Common Structural Rules for double-hull oil tankers. It is shown that hull-girder failure probability of "as-built" chemical tanker is well above the upper reliability bound proposed by IMO, while the "corroded" ship is slightly unconservative since the reliability index is lower than IMO lower reliability bound.

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.

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