Vertical and horizontal bending moments on the hydroelastic response of a large-scale segmented model in a seaway

2021 ◽  
Vol 79 ◽  
pp. 103060
Author(s):  
Jialong Jiao ◽  
Huilong Ren ◽  
C. Guedes Soares
Keyword(s):  
Large Scale ◽  
Bending Moments ◽  
Segmented Model ◽  
Hydroelastic Response

THE INFLUENCE OF CENTRE BOW LENGTH ON SLAMMING LOADS AND MOTIONS OF LARGE WAVE-PIERCING CATAMARANS

2021 ◽  
Vol 160 (A1) ◽  
Author(s):  
J R Shahraki ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Wave Height ◽  
Full Scale ◽  
Bending Moments ◽  
Regular Waves ◽  
Large Wave ◽  
Towing Tank ◽  
Segmented Model ◽  
Model Experiments ◽  
Slamming Load ◽  
Wave Induced

The effect of various centre bow lengths on the motions and wave-induced slamming loads on wave-piercing catamarans is investigated. A 2.5 m hydroelastic segmented model was tested with three different centre bow lengths and towed in regular waves in a towing tank. Measurements were made of the model motions, slam loads and vertical bending moments in the model demi-hulls. The model experiments were carried out for a test condition equivalent to a wave height of 2.68 m and a speed of 20 knots at full scale. Bow accelerations and vertical bending moments due to slamming showed significant changes with the change in centre bow, the longest centre bow having the highest wave-induced loads and accelerations. The increased volume of displaced water which is constrained beneath the bow archways is identified as the reason for this increase in the slamming load. In contrast it was found that the length of centre bow has a relatively small effect on the heave and pitch motions in slamming conditions.

Experimental study on the progressive collapse mechanism in the braced and tied-back retaining systems of deep excavations

2020 ◽  
Author(s):  
Gang Zheng ◽  
Yawei Lei ◽  
Xuesong Cheng ◽  
Xiyuan Li ◽  
Ruozhan Wang
Keyword(s):  
Large Scale ◽  
Large Deformations ◽  
Load Transfer ◽  
Progressive Failure ◽  
Progressive Collapse ◽  
Collapse Mechanism ◽  
Bending Moments ◽  
Failure Path ◽  
Transfer Mechanisms ◽  
Very High

Collapses of braced or tied-back excavations have frequently occurred. However, the influence of the failure of some retaining structure members on the overall safety performance of a retaining system has not been studied. Model tests of failures of retaining piles, struts or anchors were conducted in this study, and the load transfer mechanisms underlying these conditions were analysed. When failures or large deformations occurred in certain piles, the increasing ratios of the bending moments in adjacent piles were much larger in the braced retaining system than in the cantilever system and more easily triggered progressive failure. When the strut elevation was lower or the excavation depth was greater, the degree of influence and range of pile failures became larger. When certain struts/anchors failed, their loads transferred to a few adjacent struts/anchors, possibly leading to further strut/anchor failure. The influence mechanisms of strut or anchor failure on piles were different from those of pile failure. As the number of failed struts or anchors increases, the bending moments of the piles in the failure zone first decrease and then increase to very high values. Therefore, the progressive failure path extends from struts/anchors to piles and will lead to large-scale collapse.

Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

2016 ◽  
Author(s):  
Hui Li ◽  
Di Wang ◽  
Cheng Ming Zhou ◽  
Kaihong Zhang ◽  
Huilong Ren
Keyword(s):  
Natural Frequency ◽  
Design Stage ◽  
Resonant Vibration ◽  
Bending Moments ◽  
Wave Loads ◽  
Regular Waves ◽  
Segmented Model ◽  
Ship Model ◽  
Hull Structure ◽  
Stiffness Distribution

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

scholarly journals Nonlinear bending moments of an ultra large container ship in extreme waves based on a segmented model test

2022 ◽  
Vol 243 ◽  
pp. 110335
Author(s):  
Ying Tang ◽  
Shi-Li Sun ◽  
Rui-Song Yang ◽  
Hui-Long Ren ◽  
Xin Zhao ◽  
...  
Keyword(s):  
Model Test ◽  
Container Ship ◽  
Bending Moments ◽  
Extreme Waves ◽  
Nonlinear Bending ◽  
Segmented Model ◽  
Large Container

The Influences of Centre Bow Length on Slamming Loads and Motions of Large Wave-Piercing Catamarans

2018 ◽  
Vol Vol 160 (A1) ◽  
Author(s):  
J R Shahraki ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Wave Height ◽  
Full Scale ◽  
Bending Moments ◽  
Regular Waves ◽  
Large Wave ◽  
Towing Tank ◽  
Segmented Model ◽  
Model Experiments ◽  
Slamming Load ◽  
Wave Induced

The effect of various centre bow lengths on the motions and wave-induced slamming loads on wave-piercing catamarans is investigated. A 2.5 m hydroelastic segmented model was tested with three different centre bow lengths and towed in regular waves in a towing tank. Measurements were made of the model motions, slam loads and vertical bending moments in the model demi-hulls. The model experiments were carried out for a test condition equivalent to a wave height of 2.68 m and a speed of 20 knots at full scale. Bow accelerations and vertical bending moments due to slamming showed significant changes with the change in centre bow, the longest centre bow having the highest wave-induced loads and accelerations. The increased volume of displaced water which is constrained beneath the bow archways is identified as the reason for this increase in the slamming load. In contrast it was found that the length of centre bow has a relatively small effect on the heave and pitch motions in slamming conditions.

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.

Hydroelastic Analysis and Experimental Validation of a 350,000 DWT Very Large Crude Carrier

2017 ◽  
Author(s):  
Yuan Lin ◽  
Ning Ma ◽  
Deyu Wang ◽  
Xiechong Gu
Keyword(s):  
Numerical Simulation ◽  
Experimental Validation ◽  
Irregular Waves ◽  
Strength Analysis ◽  
Response Analysis ◽  
Bending Moments ◽  
Time Histories ◽  
Hydroelastic Analysis ◽  
Hydroelastic Response ◽  
Full Loading

Hydroelastic response of Very Large Crude Carrier (VLCC), such as springing and whipping, is very important for the fatigue strength analysis. In the present paper, numerical simulation and model test are conducted simultaneously on the springing responses of a 350,000DWT VLCC. The numerical simulation results are obtained by combining 2-D strip method and 3-D Finite Element Method (FEM) in the frequency domain. Meanwhile, the segmented model tests are conducted in three conditions. Additionally, the experimental time histories of wave bending moments in regular and irregular waves are presented. In conclusion, the methods and results presented in this paper have shown that the springing would be much easier when the VLCC is in ballast condition or the full loading conditions with reduced stiffness. The springing response will happen, when the wave encounter frequency is near to the half and one third of the ship’s flexural natural frequency. The numerical method presented is available for springing response analysis quickly with acceptable accuracy.

Effects of Water Height and Floodgate Distance on Flow Pressure of Flood

2012 ◽  
Vol 433-440 ◽  
pp. 6195-6204
Author(s):  
Shi Yun Xiao ◽  
Yi Qing Si ◽  
Bin Yue ◽  
Liu Juan Yang ◽  
Xue Li Ge ◽  
...  
Keyword(s):  
Large Scale ◽  
Bending Moment ◽  
Small Scale ◽  
Bending Moments ◽  
Building Models ◽  
Flow Surface ◽  
Flow Pressure ◽  
The Relationship ◽  
Surface Increase ◽  
Water Height

Rural building models were tested to research the action of flood on buildings, three different water heights with 0.6, 0.9 and 1.2 meters were applied to this experiment to simulate small-scale, medium-scale and large-scale flood respectively. The model was placed at 3, 6 and 9 meters far from the floodgate. In this paper, the effect of the water height and the distance between model and floodgate on the values and distributions of the flow pressure are studied. Some conclusions can be drawn: the flow pressures, force and bending moments of the flow surface increase with the increasing water height and the relationship are approximately linear; the values and distributions of the flow pressure are independent of the floodgate distance and the force and bending moment of the flow surface increase with the distance from 3 meter to 6 meter but decrease with the distance from 6 meter to 9 meter.

scholarly journals Large-Scale Model Test of a Micropile Group for Landslide Control

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xueling Liu ◽  
Jinkai Yan ◽  
Lei Liu ◽  
Bing Han
Keyword(s):  
Model Test ◽  
Large Scale ◽  
Bending Moment ◽  
Scale Model ◽  
Resistance Force ◽  
Bending Moments ◽  
Sliding Surface ◽  
Damage Area ◽  
Large Scale Model ◽  
Negative Bending

A large-scale model test on the interaction between a micropile group and a landslide was conducted, to investigate the effect of micropiles on the landsides prevention. The bearing mechanism, force condition, and failure mode of a micropile group for reinforcing landslide were analyzed in detail. The results showed that the thrust force over micropiles induced by landslide showed a trapezoidal distribution, with a higher Earth pressure near the sliding surface. The resistance from the sliding body behind the pile behaved in a parabolically trend. Meanwhile, the resistance force from the sliding bed was distributed unevenly along the height direction, with a higher resistance force near the sliding surface behind the pile. When a landslide occurred, micropiles were subjected to an increase in loading and displacement, eventually to the failure state. The load-bearing sections of the micropiles were all subjected to negative bending moments, with larger bending moments within the half length of pile range near the sliding surface. The maximum negative bending moment occurred at the height of seven times the diameter of the pile above the sliding surface. The damage mode along each row of micropiles was almost the same, showing a damage area within the range of three times the diameter of the pile above and below the sliding surface. The failure of micropile induced by landslides was mainly due to a combination effect of bending and shearing near the sliding surface.

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