Short Term Statistics of Hydroelastic Loads of a Containership in Head and Oblique Seas

2018 ◽  
Author(s):  
Suresh Rajendran ◽  
C. Guedes Soares
Keyword(s):  
Frequency Response ◽  
Bending Moment ◽  
Structural Safety ◽  
Oblique Waves ◽  
High Frequency Response ◽  
Nonlinear Design ◽  
Load Calculation ◽  
Bow Flare ◽  
Large Container ◽  
Vertical Bending Moment

Vertical bending moment (VBM) is an important parameter for the structural safety of any sea going ship. Generally, it is expected that ships encounter largest VBM in head seas. However, when it comes to flexible ships, it is not necessary that the largest VBM always occurs in head sea. It can also occur in oblique waves and high frequency response in waves with shorter period can be as large as the wave frequency response or can be even larger. Studies conducted in the recent past by other researchers has shed some light into this peculiar characteristics of VBM of flexible hulls. Therefore, it will be worthwhile to further investigate to check whether the nonlinear design load calculation of the flexible hull in head seas will lead to conservative results or should be tested for a range of headings with different combinations of wave period in order to estimate the largest VBM acting on the hull. In this paper, the numerical and the measured VBM of an ultra large container ship (ULCS) in low to severe sea states are analyzed and compared. The effect of speed, significant wave height, springing and bow flare slamming on the response is studied. The measured VBM in head and oblique waves are compared and interesting findings are observed.

Influence of Wave Group Characteristics on Loads in Severe Seas

2011 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Matthias Dudek ◽  
Marco Klein
Keyword(s):  
Critical Loads ◽  
Target Position ◽  
Bending Moment ◽  
Ship Design ◽  
Main Question ◽  
Wave Group ◽  
Regular Waves ◽  
Worst Case ◽  
Bow Flare ◽  
Vertical Bending Moment

The precise knowledge of loads and motions in extreme sea states is indispensable to ensure reliability and survival of ships and floating offshore structures. In the last decades, several accidents in severe weather with disastrous consequences have shown the need for further investigations. Besides the sea state behavior and the local structural loads, one key parameter for safe ship design is the vertical bending moment. Previous investigations revealed that different ship design criteria, such as bow geometry and wave board height, affect the global loads significantly. Investigations in regular waves as well as in single high waves of vessels with different bow flares and freeboard heights show that the vertical bending moment increases significantly with increasing bow flare and freeboard height. Furthermore it became apparent that critical loads and motions do not have to come along with the highest wave which results in the main question of this paper: What is the worst case scenario — the highest rogue wave or a wave group with certain frequency characteristics? Which sea states have to be taken into account for the experimental evaluation of limiting criteria? This paper presents investigations in different critical wave sequences, i.e. two real-sea registrations accompanied by results in regular waves to evaluate the influence of the encountering wave characteristics on the vertical bending moment. For the model tests in the seakeeping basin of the Technical University Berlin a segmented RoRo vessel with large bow flare has been built at a scale of 1:70 and equipped with force transducers. The paper proves that critical loads and motions depend most notably on combinations of wave height, wave group sequences, crest steepness, encountering speed and the ships target position: Even small wave heights with unfavorable wave lengths can cause a critical situation.

Examination of Effect of Lateral Loads on the Hull Girder Ultimate Strength of Large Container Ships

2016 ◽  
Author(s):  
Toshiyuki Matsumoto ◽  
Toshiyuki Shigemi ◽  
Mitsuhiko Kidogawa ◽  
Kinya Ishibashi ◽  
Kei Sugimoto
Keyword(s):  
Ultimate Strength ◽  
Bending Moment ◽  
Lateral Loads ◽  
Hull Girder ◽  
Local Strength ◽  
The Difference ◽  
Collapse Behavior ◽  
Large Container ◽  
Vertical Bending Moment

It is known that the hull girder ultimate strength with consideration of lateral loads such as bottom sea pressures and/or cargo loads generally decreases than that without consideration of the lateral loads (i.e. the effect of lateral loads). In this study a series of elasto-plastic analyses of three cargo holds models, which can reproduce the collapse behavior of the hold structures subjected to both vertical bending moment and lateral loads such as bottom sea pressures, container cargo loads etc., were carried out on a number of container ships with various sizes, and the hull girder ultimate strength obtained through the analyses were comparatively examined focusing on the effect of the lateral loads. As results of the examination, it has been concluded that local strength of the double bottom structure against the lateral loads is closely related to the hull girder ultimate strength in the case of container ships, the effect of the lateral loads on the hull girder ultimate strength varies among container ships due to the difference of construction of the double bottom structure and it is important to assess the hull girder ultimate strength explicitly taking into consideration the effect of the lateral loads for large container ships such as Post-Panamax sizes.

Design and Make of a Segmented Ship Model for Vertical Bending Moment Measurement

2018 ◽  
Author(s):  
Jingxia Yue ◽  
Yulong Guo ◽  
Lihua Peng
Keyword(s):  
Model Test ◽  
Large Scale ◽  
Bending Moment ◽  
Structural Safety ◽  
Scale Model ◽  
Wave Load ◽  
Scaled Model ◽  
Ship Model ◽  
Section Modulus ◽  
Vertical Bending Moment

With the development of the large-scale ship, the hull becomes more and more “soft” and “elastic”. Accurate simulation of ship’s hydro-elastic performance through scaled model test plays an important role in structural safety assessment. This paper presents the detail preparation of a segmented model which is used to investigate the vertical bending moment (VBM) for a 260m TEU container ship. Some innovative concepts were involved in the scaled model design. Firstly, the segmentation of the ship model was based on the hull’s vertical vibration mode for better simulation of the hull’s rigidity distribution. Secondly, the section of the backbone beam was varied by polishing along ship length in order to simulate the varied section modulus of ship hull. Thirdly, new backbone fixed type was carried out by two flange plates for a better wave load transmission. Besides, some useful techniques were provided, including the model making technique, calibration technique, and backbone system technique. It increases the feasibility of test, at a certain extent. Finally, an overview of the ongoing large scale model test plan and its future development directions is prospected.

scholarly journals Load calculation and strength analysis of floating garbage cleaning equipment

2021 ◽  
Vol 261 ◽  
pp. 03024
Author(s):  
Weiyao Xu ◽  
Jianting Guo ◽  
Chunyan Ji
Keyword(s):  
High Stress ◽  
Bending Moment ◽  
Strength Analysis ◽  
Floating Structure ◽  
Cleaning Equipment ◽  
Load Calculation ◽  
Calculation Results ◽  
Torque Load ◽  
Design Requirements ◽  
Vertical Bending Moment

In order to alleviate the problem that there is increasingly floating garbage pollution on the sea, this paper proposes a new design of floating garbage cleaning equipment. This equipment is a slender structure, and whether its structural strength can meet the design requirements requires special attention. In order to ensure the rationality and safety of the design, load calculation and strength analysis are carried out based on the design wave method. The calculation results show that the longitudinal torque load of this equipment is the largest, which is 2.5 times of the second largest vertical bending moment. At the same time, there are three large stress areas in the floating structure, which are the connection between the pontoon and the connecting buntons, the connecting buntons intersecting with the Y axis and the pontoons on both sides. For the abovementioned high-stress areas, a structural strengthening plan is proposed. After the improvement, the stress in the high-stress areas of the structure is significantly reduced, with a maximum reduction of 52%. The strength of the improved structure meets the design requirements. The research results of this paper can provide relevant references for the development of floating garbage cleaning equipment in the future.

Numerical Investigation Into Uncertainty of Wave-Induced Vibration of Large Container Ships due to Ship Operation

2017 ◽  
Author(s):  
Kazuhiro Iijima ◽  
Rika Ueda ◽  
Masahiko Fujikubo
Keyword(s):  
Time Series ◽  
Bending Moment ◽  
Forward Speed ◽  
Sea State ◽  
Large Container ◽  
Hydroelastic Response ◽  
Wave Induced ◽  
Ship Operation ◽  
Vertical Bending Moment ◽  
Ship Speed

A series of seakeeping simulations accounting for the wave-induced vibration is performed on three large container ships with different sizes. Time series of bodily motions, accelerations and stress due to vertical bending moment are calculated for the three ships navigating in a short-term sea state. Ship forward speed is varied from 0 knot to 20knots to investigate the sensitivity of the hydroelastic response to the change of the speed. Statistical analysis is made over the time series results, and the results are compared in terms of significant value. The uncertainty of the wave-induced vibration with respect to the ship speed is evaluated for the respective ships. It is found out that the increase rate of pitch motion, accelerations and stress to the increase of the ships’ forward speed is different from each other. It is further observed that the acceleration and vertical bending moment increase is less prominent for the largest ship.

High Frequency Response of Magnetization of Thin-Film Heads

1992 ◽  
Vol 7 (10) ◽  
pp. 773-778
Author(s):  
S. Narumi ◽  
S. Sudo ◽  
M. Aihara ◽  
H. Fukui
Keyword(s):  
Thin Film ◽  
Frequency Response ◽  
High Frequency ◽  
High Frequency Response
Sign in / Sign up

Export Citation Format

Share Document