Large Containerships’ Fatigue Analysis due to Springing and Whipping

2016 ◽  
Author(s):  
Huilong Ren ◽  
Kaihong Zhang ◽  
Hui Li ◽  
Di Wang
Keyword(s):  
Statistical Analysis ◽  
Fatigue Damage ◽  
Time Domain ◽  
High Frequency ◽  
Influence Factor ◽  
Irregular Waves ◽  
Wave Loads ◽  
Analysis Method ◽  
Load Case ◽  
Factor Modification

As the sea transport demand increases constantly, marine corporations around the world are pursuing solutions with large scale and low cost, which makes ultra large containerships’ construction consequentially. Ultra large containerships are more flexible relatively, and the 2-node natural frequency can easily fall into the encountered spectrum frequency range of normal sea state. Meanwhile, as the speed of containerships is high and its large bow flare, when sailing with high speed, the bow structures may suffer severe slamming forces which can increase the design wave loads’ level and the fatigue damage. The importance of hydroelastic analysis of large and flexible containerships of today has been pointed out for structure design. Rules of Many Classification Society have made changes on design wave loads’ value and fatigue influence factor modification. The paper firstly introduced 3-D linear hydroelasticity theory to calculate the Response Amplitude Operator (RAO) in frequency domain, and then described 3-D nonlinear hydroelasticity theory to obtain the nonlinear wave loads time history in irregular waves in time domain, considering large amplitude motion and slamming force due to severe relative motion between ship hull and wave. Based on the theories, computer programs are made to conduct the calculations under specified load case, and some calculation and statistical results are compared with experimental results to verify the accuracy and stability of the programs secondly. The paper focused on the influence of springing and whipping on fatigue damages of 8500TEU and 10000TEU containerships in different loading cases, using spectrum analysis method and time domain statistical analysis method. The spectrum analysis method can calculate fatigue damage due to low-frequency wave loads and high-frequency springing separately, while the time domain statistical analysis can calculate fatigue damage due to the high-frequency damping whipping additionally, based on 3-D time domain nonlinear hydroelasticity wave loads’ time series simulation in irregular waves and rain flow counting method. Finally, discussions on influence factor of springing and whipping with different loading cases are made. Based on these two containerships in example, the fatigue damage due to whipping can be the same as the fatigue damage due to springing and even sometimes can be larger than the springing damage. According to the wave loads influence factor, the fatigue assessment of different position on midship section is done on the basis of nominal stress. Besides, some suggestions on calculating load case selection are made to minimize the quantity of work in frequency and time domain. Thus the tools for fatigue influence factor modification are provided to meet the demand of IACS’ UR[1].

The Effect on Large Container Ships’ Fatigue due to Springing Loads Coupling Horizontal and Torsional Vibrations

2018 ◽  
Author(s):  
Hui Li ◽  
Huifen Xu ◽  
Huilong Ren ◽  
Xiaoxi Shen ◽  
Yubo Wang
Keyword(s):  
Fatigue Damage ◽  
Torsional Vibration ◽  
Calculation Method ◽  
Wave Loads ◽  
Analysis Method ◽  
Element Analysis ◽  
Hull Structure ◽  
Torsional Loads ◽  
Large Container ◽  
Simplified Calculation

The issue of hydroelasticity caused by hull vibration has become an unavoidable problem in the design and verification of large ships. Driven by environmental protection and economical efficiency, the size of ships are increasingly larger, and the resulting springing and whipping response and their effects on fatigue damage has been paid more and more attention especially for ultra large container ships (ULCS). Many classification societies typically check fatigue damage caused by vertical bending when considering springing, while it needs to be emphasized that large container ships can suffer severe torsional loads compared to other large ships due to wide breath and big hatch openings. In the existing stress calculation method, the finite element analysis method obviously has a high calculation accuracy. However, there are so much work to do with FEM model established, and partially refined, operated at all sea states etc., which not only requires much time, but also higher computing equipment. Therefore, in this paper, a simplified calculation method of fatigue damage considering the effect of bending and torsion is proposed, and a 21000TEU will be calculated by this method. The wave loads on the hull structure will be estimated based on the 3D linear hydroelastic theory coupling horizontal and torsional vibration, and the stress caused by bending and torsion will be obtained respectively. Finally, the fatigue damage is calculated by spectral analysis method considering high frequency springing loads. Then the effect on large container ships’ fatigue due to bending and torsional vibration is discussed.

Frequency Versus Time Domain Fatigue Analysis of a Semisubmersible Wind Turbine Tower

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Marit I. Kvittem ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Time Domain ◽  
Low Frequency ◽  
Bending Moment ◽  
Good Representation ◽  
Bending Moments ◽  
Wave Loads ◽  
Flexible Mode ◽  
Standard Deviations

The current paper deals with a study of a semisubmersible wind turbine (WT), where short-term tower base bending moments and tower fatigue damage were estimated by a frequency domain (FD) method. Both a rigid structure assumption and a generalized degree-of-freedom (DOF) model for including the first flexible mode of the turbine tower were investigated. First, response to wind and wave loads was considered separately, then superposition was used to find the response to combined wind and wave loading. The bending moments and fatigue damage obtained by these methods were compared to results from a fully coupled, nonlinear time domain (TD) analysis. In this study a three column, catenary moored semisubmersible with the NREL 5 MW turbine mounted on one of the columns was modeled. The model was inspired by the WindFloat concept. The TD simulation tool used was Simo-Riflex-AeroDyn from Marintek and CeSOS. The FD method gave a good representation of the tower base bending moment histories for wave-only analyses, for the moderate sea states considered in these analyses. With the assumption that the structure is completely rigid, bending moments were underestimated, but including excitation of the elastic tower and blades, improved the results. The wind-induced low-frequency bending moments were not captured very well, which presumably comes from a combination of nonlinear effects being lost in the linearization of the thrust force and that the aerodynamic damping model was derived for a fixed turbine. Nevertheless, standard deviations of the bending moments were still reasonable. The FD model captured the combined wind and wave analyses quite well when a generalized coordinates model for wind excitation of the first bending mode of the turbine was included. The FD fatigue damage predictions were underestimated by 0–60%, corresponding to discrepancies in standard deviations of stress in the order of 0–20%.

A Fast and Practical Method for Predicting the Fatigue Life of Offshore Wind Turbine Jacket Support Structures

2017 ◽  
Author(s):  
Chaoshuai Han ◽  
Yongliang Ma ◽  
Xianqiang Qu ◽  
Peijiang Qin ◽  
Binbin Qiu
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Time Domain ◽  
Practical Method ◽  
Computational Effort ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Support Structures

Fatigue assessment is a very important part in the design process of offshore wind turbine support structures subjected to wind and wave loads. Fully coupled time domain simulations due to wind and wave loads can potentially provide reliable fatigue predictions, however, it will take high computational effort to carry out fatigue analysis of the simultaneous wind and wave response of the support structure in time domain. For convenience and reducing computational efforts, a fast and practical method is proposed for predicting the fatigue life of offshore wind turbine jacket support structures. Wind induced fatigue is calculated in the time domain using ANSYS based on rainflow counting, and wave induced fatigue is computed in frequency domain using SACS based on a linear spectral analysis. Fatigue damage of X-joints and K-joints under combined environmental loads of wind and wave is estimated by using the proposed method. To verify the accuracy of the proposed formula, fatigue damage based on time domain rainflow cycle counting is calculated and can be considered as a reference. It is concluded that the proposed method provides reasonable fatigue damage predictions and can be adopted for evaluating the combined fatigue damage due to wind and wave loads in offshore wind turbine.

scholarly journals Discussion on the Application of Statistical Analysis Method in Geography Education Research —— Taking Drought and Snow Disaster in Xilingol League as an Example

2021 ◽  
Vol 4 (2) ◽  
pp. 28
Author(s):  
Jingbo Cao
Keyword(s):  
Statistical Analysis ◽  
El Niño ◽  
High Frequency ◽  
El Nino ◽  
Geography Education ◽  
La Niña ◽  
Analysis Method ◽  
La Nina ◽  
Statistical Analysis Method ◽  
Temporal And Spatial

Based on the statistical analysis method, this paper studies the temporal and spatial correlation between drought and snow Based on the statistical analysis method, this paper studies the temporal and spatial correlation between drought and snow disasters and El Nino/La Nina events in various counties of Xilingol League. According to the research results, it is found that the number of disasters in Xilingol League in El Nino/La Nina year accounts for 54% of the total number of disasters in Xilingol League. El Nino has more disasters than La Nina. In El Nino/La Nina years, the frequency of snow disasters in Xilingol League is higher than that of drought disasters. The areas with high frequency of El Nino disasters are East Ujimqin Banner, West Ujimqin Banner and Abaga Banner. The areas with high frequency of disasters in La Nina are Sonid Zuoqi, Erenhot, Xilinhot and Xianghuang Banner. Using statistical analysis method can accurately and effectively study whether there is obvious correlation between drought and snow disasters and El Nino/La Nina events in Xilingol League, and enrich the methods and contents in geography education and research, which is of great significance for monitoring and preventing drought and snow disasters in Xilingol League.

Prediction of Nonlinear Acceleration Response of a Large Container Ship and the Validation of Excessive Acceleration Failure Mode

2021 ◽  
Author(s):  
Fei Duan ◽  
Ning Ma ◽  
Xiechong Gu ◽  
Yaohua Zhou ◽  
Wang Shangming
Keyword(s):  
Time Domain ◽  
Failure Modes ◽  
Influence Factor ◽  
Experimental Results ◽  
Irregular Waves ◽  
Lateral Acceleration ◽  
Container Ship ◽  
Acceleration Response ◽  
Intact Stability ◽  
Large Container

Abstract The excessive acceleration is one of five stability failure modes for intact stability being discussed at IMO. The excessive acceleration usually occurs in shallow draft state, under which the ship is prone to large nonlinear rolling motion. Therefore, the accurate prediction and evaluation of the acceleration response are required in ship intact stability analysis. This paper proposes a 5-DOF model in time domain to calculate the nonlinear acceleration response of a large container ship. The nonlinear restoring force and wave exciting forces (F-K force) are calculated through pressure integration on instantaneous wetted surfaces. A model test has been carried out to verify the prediction method of ship nonlinear acceleration response in the regular and irregular waves. It turns out the ship nonlinear acceleration response in regular and irregular waves obtained by the nonlinear time domain simulation agrees well with the experimental results. The vulnerability criteria for excessive acceleration are also validated by numerical and experimental results. In addition, the influence factor of ship lateral acceleration is studied. The results show that the prediction accuracy of 5-DOF model is acceptable. However, the accuracy needs to be improved for the condition of short wavelength. The influence of angular velocity can be ignored.

Vibration Analysis of Silicon Microgyroscope Based on Simulink

2014 ◽  
Vol 670-671 ◽  
pp. 1310-1314
Author(s):  
Wei Feng Tang ◽  
An Ping Qiu ◽  
Guo Ming Xia ◽  
Yan Su
Keyword(s):  
Time Domain ◽  
Vibration Analysis ◽  
Influence Factor ◽  
Structure Design ◽  
Interior Structure ◽  
Analysis Method ◽  
Signal Conversion ◽  
Bias Stability ◽  
Method Base ◽  
Main Influence

To improve the anti-vibration capability of silicon mcrogyroscope, making it works well under the vibration environment, this paper analyzes the dual-mass silicon mcrogyroscope and did the following works. First of all, the operating principle, analysis parameters of silicon microgyroscope and the vibration condition are introduced. Secondly, this paper proposes a vibration analysis method base on the signal conversion between time domain and frequency domain and establishes a Simulink demodulation model according to circuits of silicon microgyroscope. Finally, we get the conclusion that under the condition of vibration, composition with the same frequency of Vds in Vsense signal is the main influence factor of bias stability by analyzing experimental data. This has a great significance for improving the anti-vibration capability and guiding the interior structure design of silicon microgyroscope.

Management of Guidance and Counseling on Learning Discipline

2020 ◽  
Vol 10 (2) ◽  
pp. 60-74
Author(s):  
Muhammad Syauqi Mubarok
Keyword(s):  
Statistical Analysis ◽  
Descriptive Analysis ◽  
Field Studies ◽  
Guidance And Counseling ◽  
Analysis Method ◽  
Vocational High School ◽  
Analysis Model ◽  
Survey Techniques ◽  
Analysis Technique ◽  
Path Analysis Model

This article aims to examine and describe the influence of guidance and counseling management on learning discipline. The method used in this research is descriptive analysis method using survey techniques. Data collection techniques that used are documentation studies and field studies. Moreover, the data analysis technique that has been used to answer the research hypothesis is statistical analysis with a path analysis model. The location of the study was at the Ciledug Vocational High School Al-Musaddadiyah Garut, with 85 respondents taking part in the survey. The results of the discussion show that guidance and counseling management has a positive and significant effect on the discipline of learning

PENGARUH KINERJA PENGELOLAAN KEUANGAN DAERAH TERHADAP PERTUMBUHAN EKONOMI, PENGANGGURAN DAN KEMISKINAN DI KOTA DEPOK

2019 ◽  
Vol 2 (2) ◽  
pp. 372
Author(s):  
Suryanta Suryanta
Keyword(s):  
Economic Growth ◽  
Statistical Analysis ◽  
Financial Management ◽  
Regression Coefficient ◽  
Descriptive Analysis ◽  
Analysis Method ◽  
Simple Linear Regression ◽  
Quantitative Descriptive Analysis ◽  
Income Gap ◽  
Quantitative Descriptive

This study aims to analyze whether the performance of regional financial management influences economic growth in Depok City, analyzes whether the performance of regional financial management influences unemployment in Depok City, and analyzes whether the performance of regional financial management affects poverty in Depok City with the 2006 study period- 2015 The analysis method used is quantitative descriptive analysis and simple linear regression statistical analysis. Based on the results of hypothesis testing it can be proven that the performance of regional financial management (independence ratio) has a positive and significant effect on economic growth, this can be seen from the value of sig. 0.046 <0.05 with a regression coefficient of 1.883. Then the performance of regional financial management has a negative and significant effect on unemployment, this can be seen from the value of sig. 0.030 <0.05 with a regression coefficient of -6.864. But the performance of regional financial management has no significant effect on poverty, this can be seen from the sig. 0.065> 0.05 with a regression coefficient of -0.512. This can be due to the still high income gap in the community, so that the increasing regional income has not been able to significantly reduce poverty in Depok.

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