Charts for Estimating Nonlinear Hogging and Sagging Bending Moments

1995 ◽  
Vol 39 (03) ◽  
pp. 240-249
Author(s):  
A. E. Mansour ◽  
J-P. Wasson
Keyword(s):  
Vertical Wall ◽  
Nonlinearity Parameter ◽  
Bending Moments ◽  
Strip Theory ◽  
The Difference

Abstract This paper presents charts for preliminary estimates of the nonlinearities associated with wave bending moments acting on a ship moving in a stationary sea. Deviation of the actual hull shape above the waterline from "vertical wall" is characterized by a flare coefficient. The charts show the influence of the flare coefficient, among other parameters, on a nonlinearity parameter which may be used to estimate the difference between wave hogging and sagging moments. Three application examples are given at the end of the paper to illustrate how the charts can be used in conjunction with linear strip theory results in order to estimate slightly nonlinear hogging and sagging moments.

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.

A comparison of root and stem lodging risks among winter wheat cultivars

2003 ◽  
Vol 141 (2) ◽  
pp. 191-202 ◽  
Author(s):  
P. M. BERRY ◽  
J. H. SPINK ◽  
A. P. GAY ◽  
J. CRAIGON
Keyword(s):  
Winter Wheat ◽  
Bending Moments ◽  
Wheat Cultivars ◽  
Lodging Resistance ◽  
Wind Speeds ◽  
Winter Wheat Cultivars ◽  
Related Plant ◽  
The Difference ◽  
Root Lodging ◽  
Stem Failure

Plant characters that determine stem and root lodging were measured on 15 winter wheat cultivars at three UK sites between 2000 and 2002. A model of lodging was used to estimate stem failure wind speeds (resistance to stem lodging) and anchorage failure wind speeds (resistance to root lodging). The degree and type of natural lodging was also recorded in the plots and this correlated well with the stem and anchorage failure wind speeds. Only a weak correlation (R2=0·33) was observed between the stem and anchorage failure wind speeds for the 15 cultivars. This can be explained by the absence of genetic correlation between the plant characters that determine the stem and anchorage strength. There was a significant interaction between type of lodging (stem or root) and cultivar for failure wind speed (P<0·001). This showed that the difference between the resistances for root and stem lodging was not the same for all cultivars. Separate classifications for the stem and root lodging resistance of cultivars are developed that would allow the most appropriate crop management to reduce the risk of both types of lodging. Significant differences were found between cultivars for all lodging-related plant characters (P<0·05). These resulted in the cultivar range of the anchorage failure moment to be 110% of the overall mean. Stem failure moment, shoot and plant base bending moments had ranges of 37–49% of their overall means. Breeders should select for wide, deep root plates and wide stems with a high stem wall failure yield stress for the greatest improvement in lodging resistance.

FEM Stress Analysis and Mechanical Characteristics of Bolted Pipe Flange Connections With PTFE Blended Gaskets Subjected to External Bending Moments and Internal Pressure

2017 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Riichi Morimoto ◽  
Takashi Kobayashi
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Bending Moment ◽  
Leak Rate ◽  
Bending Moments ◽  
Four Point Bending ◽  
Sealing Performance ◽  
The Difference ◽  
Good Agreement

In designing of pipe flange connections with gaskets, it is important to examine the mechanical characteristics of the connections subjected to external bending moments due to earthquake such as the changes in hub stress, axial bolt forces and the contact gasket stress distribution which governs the sealing performance. One of the authors developed the PTFE blended gaskets and the authors examined the mechanical characteristics of the connections with the PTFE blended gaskets under internal pressure. However, no research was done to examine the mechanical characteristics of the connections with the newly developed PTFE blended gasket subjected to external bending moment due to earthquake. The objectives of the present study are to examine the mechanical characteristics of the connection with PTFE blended gasket subjected to external bending moment and internal pressure and to discuss the difference in the load order to the connections between the internal pressure and the external bending moments. The changes in the hub stress, the axial bolt force and the contact gasket stress distribution of the connection are analyzed using FEM. Using the obtained the gasket stress distribution and the fundamental data between the gasket stress and the leak rate for a smaller test gasket, the leak rate of the connection with the gasket is predicted under external bending moment and internal pressure. In the FEM calculations, the effects of the nominal diameter of pipe flanges on the mechanical characteristics are shown. In the experiments, ASME class 300 4 inch flange connection with 2m pipes at both sides is used and the test gasket is chosen as No.GF300 made by Nippon Valqua Industries, ltd. Four point bending moment is applied to the connection. The FEM results of the hub stress and the axial bolt forces are in a fairly good agreement with the experimental results. In addition, the FEM results of the leak rate are fairly coincided with the measured results.

A Topographical Approach to Parietal Figures: The Monumental Sculptures of the Roc-aux-Sorciers (Vienne, France) Produced in Daylight at the Back of a Rockshelter and on its Ceiling

2007 ◽  
Author(s):  
Geneviéve Pinçon
Keyword(s):  
Spatial Organization ◽  
Vertical Wall ◽  
Upstream Part ◽  
The Difference ◽  
The Right

The wonderful discovery of parietal figures in the entrance chamber of Church Hole by P. Bahn, P. Pettitt and S. Ripoll in 2003 invites us to study the elements that are linked to the topography of parietal figures made on ceilings in daylight. At Creswell, early excavations had revealed Magdalenian occupations. This association between habitation and parietal figures recalls other contexts, such as for example that of the Roc-aux-Sorciers at Angles-sur-l’Anglin (Vienne, France). This Magdalenian site contains a sculpted, engraved, and painted parietal assemblage which extends for more than 50 m at the foot of the cliff along the Anglin River. The upstream part of the site, called the Taillebourg cave, and which corresponds to a typical vestibule, yielded numerous decorated blocks that came from a major collapse of the cave’s ceiling; their refitting is currently under way. The downstream part, known as the abri Bourdois, which is a shallow overhang, at present contains a sculpted, engraved, and painted frieze, almost 20 m long, located on the vertical wall at the back of the rockshelter. Today the shelter’s ceiling has no traces of sculpture or engraving, but nothing confirms or rules out the presence of parietal figures here in the Magdalenian. After an analysis of the spatial organization of the figures in the abri Bourdois, we shall look at the elements at our disposal for understanding the figures on the ceiling of the Taillebourg cave in order to grasp whether the difference in location and the morphology of the supports had any impact on the spatial organization of the figures in the site as a whole. The site of the Roc-aux-Sorciers is located in Poitou-Charentes, in central-west France, in the commune of Angles-sur-l’Anglin. It was oficially classed as a historical monument on 18 January 1955. Facing directly south, it extends for about 50 m, at the foot of cliffs, near the present-day village, on the right bank of the Anglin (Fig. 12.1).

scholarly journals OpenFOAM Based Approach for the Prediction of the Dam Break with an Obstacle

2020 ◽  
Author(s):  
Richmond Sam Quarm
Keyword(s):  
Numerical Solution ◽  
Vertical Wall ◽  
Leading Edge ◽  
Numerical Approach ◽  
Dam Break ◽  
Free Surface Elevation ◽  
Before And After ◽  
The Difference ◽  
The Impact ◽  
Simulation Time

The phenomenon of the flow impact on a vertical wall resulting from a dam problem is simulated by using OpenFOAM. In this simulation, a dam break was also simulated with the addition of obstacles with various dimensions. The aim of this study is to assess the accuracy of the solver for problems in the impact wave category from the experimental results of previous researchers and other numerical solution techniques compared with the results of this solver. Different aspects of flow such as free surface elevation before and after the initial impact have been observed in depth. The method used in this research is numerical computation simulation with the OpenFOAM approach which has the advantage of being more accurate and fast simulation time. The variations in the dimensions of the obstacle in this study were b / h = 0.25, b / h = 0.5 and b / h = 1.0. From the simulation data, it is found that the numerical approach has been validated through quantitative comparisons with experimental measurements. The computational positions of the leading edge of the collapsed water column match the experimental data. The difference between the experiment and this numerical solution is below 2%.

scholarly journals OpenFOAM Based Approach for the Prediction of the Dam Break with an Obstacle

2020 ◽  
Author(s):  
Mohamed Osman Elamin Busharads
Keyword(s):  
Numerical Solution ◽  
Vertical Wall ◽  
Leading Edge ◽  
Numerical Approach ◽  
Dam Break ◽  
Free Surface Elevation ◽  
Before And After ◽  
The Difference ◽  
The Impact ◽  
Simulation Time

The phenomenon of the flow impact on a vertical wall resulting from a dam problem is simulated by using OpenFOAM. In this simulation, a dam break was also simulated with the addition of obstacles with various dimensions. The aim of this study is to assess the accuracy of the solver for problems in the impact wave category from the experimental results of previous researchers and other numerical solution techniques compared with the results of this solver. Different aspects of flow such as free surface elevation before and after the initial impact have been observed in depth. The method used in this research is numerical computation simulation with the OpenFOAM approach which has the advantage of being more accurate and fast simulation time. The variations in the dimensions of the obstacle in this study were b / h = 0.25, b / h = 0.5 and b / h = 1.0. From the simulation data, it is found that the numerical approach has been validated through quantitative comparisons with experimental measurements. The computational positions of the leading edge of the collapsed water column match the experimental data. The difference between the experiment and this numerical solution is below 2%.

Evaluation of Cumulative Collapse of a LNG Carrier Hull Girder Under Dynamic Cyclic Bending Moments

2021 ◽  
Author(s):  
Jian Ji ◽  
Bin Liu ◽  
Lin Chen ◽  
Xianting Liao ◽  
C. Guedes Soares
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Failure Modes ◽  
Ship Hull ◽  
Bending Moments ◽  
Nonlinear Finite Element Method ◽  
Cyclic Bending ◽  
Hull Girder ◽  
Hull Structure ◽  
The Difference

Abstract The present paper continues the recent work reported by Liu and Guedes Soares [1] where finite element simulations were conducted to investigate the ultimate strength of a container ship hull girder under cyclic bending moments. Here a membrane LNG carrier is investigated to evaluate the “cyclic ultimate strength” of this specialized ship hull structure including double bottoms, sides and decks. The paper aims to analyze the ultimate strength and to compare the collapse modes of a LNG carrier hull girder under monotonic and dynamic cyclic bending moments, revealing the difference in their failure modes. Nonlinear finite element method is employed, using the explicit LS-DYNA solver, to analyze the ultimate strength of hull structures. The numerical results show that the cyclic ultimate strength of hull structures is about 20% lower than the monotonic ultimate strength in the present study.

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.

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