A Fatigue Design for Large Container Ship Taking Long-Term Environmental Condition Into Account

2011 ◽  
Author(s):  
Masayoshi Oka ◽  
Yoshitaka Ogawa ◽  
Ken Takagi
Keyword(s):  
Fatigue Damage ◽  
Element Model ◽  
Full Scale ◽  
Elastic Model ◽  
Direct Computation ◽  
Wave Condition ◽  
Irregular Wave ◽  
Fatigue Design ◽  
Tank Test

In order to promote the reliable evaluation for the fatigue strength of ships, the validation of a direct load and strength computation was performed based on the tank test and the full scale measurement. The fatigue damage in short term sea state under various operation parameters was indicated quantitatively by the tank test in irregular wave utilizing the elastic model. The long term fatigue damage was evaluated based on the full scale measurement [1]. The fatigue damage inferred from the measured stress on deck structure is quite small compared with the direct computation utilizing a full ship finite element model. That is mainly caused by the difference of environmental wave condition. Moreover, the effect of operational condition through whole life was indicated by the direct computation quantitatively. To make more rational fatigue design, it is important to take the long-term wave condition into account.

Comparative Study on Fatigue Damage Assessment of a Structure Member in a Bulk Carrier Using Various Environmental Conditions

2019 ◽  
Author(s):  
Fredhi Agung Prasetyo ◽  
Naoki Osawa ◽  
Mohammad Arif Kurniawan ◽  
Siti Komariyah
Keyword(s):  
Fatigue Damage ◽  
Environmental Conditions ◽  
Damage Assessment ◽  
North Atlantic Ocean ◽  
Environmental Condition ◽  
Scatter Diagram ◽  
Sea State ◽  
Fatigue Design ◽  
Design Life

Abstract Specific design life could be identified by using fatigue damage assessment in the structure engineering field as well as in the maritime sector. Fatigue assessment is one of the assessments to be conducted during review of ship structure design. Fatigue assessment of ship structural member is mainly conducted based on specific environmental condition. In general, specific environmental condition, which is provided by Classification Society rules, is a long term sea-state data of North Atlantic Ocean. The wave scatter diagram presents the tabulation of a long term data of sea state history in the specific ocean. Therefore, a realistic encounter of wave scatter diagram is essential to simulate the variation of wave loadings applied on the ship structure in determination of fatigue design life. Since the application of North Atlantic ocean environmental condition is commonly used by major Classification societies, this condition might give the substantial deterioration on the fatigue design life of the ship that specially operate only in specific ocean area, i.e. South East Asia area. In this work, the wave scatter diagram of various environmental conditions is chosen and the statistical characteristic is compared. The wave load sequence that is used on the fatigue damage assessment are generated by using the concept of storm model, so that the changing nature of sea state could be emulated as in real ocean. Fatigue damage of a structure member of 220 meter Bulk Carriers is calculated based on various environmental conditions.

Fatigue Testing of Full Scale Girth Welded Pipes Under Variable Amplitude Loading

2012 ◽  
Author(s):  
Y.-H. Zhang ◽  
S. J. Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Design ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Loading Spectrum

In the fatigue design of steel catenary risers there are concerns regarding the fatigue damage to girth welds from low stresses, below the constant amplitude fatigue limit, in the loading spectrum and the validity of Miner’s cumulative damage rule. In both cases there is increasing evidence that current design methods can be non-conservative. These fundamental issues were addressed in a recent JIP. A key feature was development of the resonance fatigue testing rigs to enable them to test full-scale pipes under variable amplitude loading. Such tests were performed under a loading spectrum representative of that experienced by some risers, with many tests lasting over 100 million cycles to investigate the fatigue damage due to small stresses as well as the validity of Miner’s rule. However, the resonance rigs are only capable of producing spectrum loading by gradually increasing or decreasing the applied load, whereas more ‘spiky’ random load sequences may be relevant in practice. Therefore the programme also included fatigue tests in conventional testing machines on strip specimens cut from pipes to compare the two types of loading sequence. This paper presents the results of these tests, conclusions drawn and recommendations for changes to current fatigue design guidance for girth welded pipes regarding the definition of the fatigue limit, allowance for the damaging effect of low stresses and the validity of Miner’s rule.

Fatigue Performance of Grade R4 and R5 Mooring Chains in Seawater

2014 ◽  
Author(s):  
Jonathan Fernández ◽  
Walther Storesund ◽  
Jesús Navas
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Fatigue Tests ◽  
Design Methods ◽  
Full Scale ◽  
Fatigue Performance ◽  
Test Program ◽  
Gas Industry ◽  
Fatigue Design ◽  
Cumulative Fatigue Damage

With more than 50.000 tons in service to date, the Oil&Gas Industry has the need to understand the tension fatigue performance of grade R5 chains in straight tension, and corroborate the validity of the existing design methods. The chain fatigue design curves in API and DNV are based on fatigue tests obtained in the nineties and early two thousands. However the tests were performed on lower grades such as ORQ, R3 and R4, and small chains, 76 mm diameter being the largest studless chain tested. The industry has moved towards the use of large studless chains, especially in permanent units, where chain diameters above 150 mm are not unusual. This paper gathers information from a full scale fatigue test program on grade R4 and R5 studless chains, performed in seawater and with diameters between 70 mm and 171 mm. The chains being tested are actual production chains supplied for different drilling units and large permanently moored production floating units. The paper analyses the data and determines tension-tension fatigue curves based on API and DNV methods for computation of cumulative fatigue damage, regardless of other damaging mechanisms. Improved fatigue capacity is obtained with respect to the above recommended design methods.

scholarly journals Representative Environmental Condition for Fatigue Analysis of Offshore Jacket Substructure

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5494
Author(s):  
Tsung-Yueh Lin ◽  
Yi-Qing Zhao ◽  
Hsin-Haou Huang
Keyword(s):  
Fatigue Damage ◽  
Environmental Conditions ◽  
Element Model ◽  
Computational Time ◽  
Wave Load ◽  
Sea State ◽  
Stress Signals ◽  
Cumulative Fatigue Damage ◽  
The Taiwan Strait

The 20-year cumulative fatigue damage of an offshore jacket substructure was estimated under the long-term local environmental conditions in the Taiwan Strait. Because of the nonlinearity of wave load for slender members of the structure, time-domain simulations of the dynamic finite element model were conducted for each sea state. By utilizing the Dirlik method to process the stress signals, the fatigue damages of joints were computed. Concerning the computational time, we propose a probability-based method of using a representative combination of environmental conditions in this study, which can considerably reduce the required number of evaluations prior to determining fatigue damage, thereby improving the process of preliminary design. The results show that only three sea states among 120 can represent 28% of the average damage ratio, and up to 17 sea states fully resolved the fatigue life.

Fatigue Testing of Full Scale Girth Welded Pipes Under Variable Amplitude Loading

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Y.-H. Zhang ◽  
S. J. Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Design ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Loading Spectrum

In the fatigue design of steel catenary risers, there are concerns regarding the fatigue damage to girth welds from low stresses, below the constant amplitude fatigue limit, in the loading spectrum and the validity of Miner's cumulative damage rule. These fundamental issues were addressed in a recent joint-industrial project (JIP). A key feature was development of the resonance fatigue testing rigs to enable them to test full-scale pipes under variable amplitude loading. Such tests were performed under a loading spectrum representative of that experienced by some risers, with many tests lasting over 100 million cycles to investigate the fatigue damage due to small stresses as well as the validity of Miner's rule. However, the resonance rigs are only capable of producing spectrum loading by gradually increasing or decreasing the applied load whereas more “spiky” random load sequences may be relevant in practice. Therefore, the program also included fatigue tests in conventional testing machines on strip specimens cut from pipes to compare the two types of loading sequence. This paper presents the results of these tests, conclusions drawn, and recommendations for changes to current fatigue design guidance for girth welded pipes regarding the definition of the fatigue limit, allowance for the damaging effect of low stresses, and the validity of Miner's rule.

Analysis of Cracks and Stresses of Welded Attachments on Full-Scale Plate Girder under Fatigue Loading

2006 ◽  
Vol 324-325 ◽  
pp. 459-462 ◽  
Author(s):  
Myung Gu Lee ◽  
Seung Yong Lee ◽  
Cheol Woo Park
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Steel Structure ◽  
Fatigue Loading ◽  
Design Criterion ◽  
Full Scale ◽  
Parent Metal ◽  
Girder Bridges ◽  
Fatigue Design ◽  
Plate Girder

In steel structure systems such as plate girder bridges and framed structures, fatigue damage used to occur at welded areas rather than primary structural members. These damages and behaviors of the welded attachments need to be extensively investigated so that the fatigue design criterion can effectively control the fatigue damage of steel structure systems. This study utilized a full-scale plate girder on which various welding attachments were mounted. The welded attachments investigated herein included flange gussets, web gussets, vertical stiffeners, and cover plates. The fatigue cracks initiated at the longitudinal end of joint area of the weld bead and the parent metal where stress was significantly concentrated. The initiated fatigue cracks developed along the weld path and then, propagated to the parent metal in the direction perpendicular to the principal stress. The fatigue cracks developed even under a compressive stress when a significant residual stress was experienced from the welding. The fatigue strengths of the each welded attachment were evaluated and compared with the current fatigue design specifications in AASHTO [1] and JSSC [2].

Development of Fatigue Testing of Full-Scale Girth Welded Pipes Under Variable Amplitude Loading

2011 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Stephen Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Cumulative Damage ◽  
Constant Amplitude ◽  
Variable Amplitude ◽  
Testing Procedures ◽  
Fatigue Design ◽  
Damage Rule

In service the great majority of structures and components are subjected to stresses of variable amplitude (VA). The fatigue design of welded joints in such structures is based on fatigue data obtained under constant amplitude loading, used in conjunction with a cumulative damage rule to estimate the damage introduced by cycles of varying magnitude in the service stress history. There are two major concerns with fatigue design of deepwater steel catenary risers (SCRs): the validity of cumulative damage rule and the damaging effect of stresses below the constant amplitude fatigue limit (CAFL). It is known that SCRs can experience very high numbers of low stress cycles due to vortex induced vibration (VIV) with the result that the choice of method for accounting for the fatigue damage due to stresses below the constant amplitude fatigue limit can be highly significant in terms of the estimated fatigue life. These two fundamental issues have been addressed in a recent group sponsored project. By successfully establishing a loading spectrum representative of that experienced by risers and developing the testing procedures for VA loading using the resonance testing rigs, the fatigue performance of full-scale girth welded pipes under VA loading were investigated. These loading spectra had the same peak/maximum stress histograms but different minimum stresses. Many tests lasted over 108 cycles to investigate the fatigue damage of small stresses in these spectra. This paper describes the development of the method by which fatigue testing of full-scale girth welded pipes under VA loading had been successfully performed.

Fatigue Variation in Ships due to the Variability of Environmental Loads

2012 ◽  
Author(s):  
Wengang Mao ◽  
Zhiyuan Li ◽  
Jonas W. Ringsberg ◽  
Igor Rychlik
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Structural Strength ◽  
Fatigue Cracks ◽  
Maritime Industry ◽  
Fatigue Design ◽  
Routing Design ◽  
Potential Use

The design and analysis of structural strength against fatigue failure always includes large uncertainties. It is crucial to understand and identify the most important uncertainties that affect the performance, functionality and service life of an engineering structure — in particular when it comes to the safety aspect, which may involve the risk of loss of human lives. In maritime industry, it is known that due to various sources of uncertainties in ship fatigue design, some ships may survive (the occurrence of fatigue cracks which may endanger the structural integrity) much longer than their designed life, while other ships develop fatigue cracks far too early. The current investigation presents some of the most important uncertainties and their effects on the accuracy of fatigue assessments in a container vessel. The study emphasizes the analysis of the fatigue damage variation when the ship is sailing on different routings between two ports. A fatigue model developed by the authors for ship fatigue routing application is employed to estimate the long term fatigue damage. In this model, only a few parameters, i.e. the encountered significant wave height and operational profiles, are needed. The procedure of using this model for a ship fatigue routing design is described in detail. Its potential use and benefits are demonstrated in a case study by a 2,800 TEU container ship using both full-scale measurements and hindcast wave data. It is shown that awareness and careful fatigue routing design can reduce fatigue damage significantly by up to 50%!

scholarly journals Rotor Loading Characteristics of a Full-Scale Tidal Turbine

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1035 ◽  
Author(s):  
Magnus Harrold ◽  
Pablo Ouro
Keyword(s):  
Turbulent Flows ◽  
Mechanical Loading ◽  
Full Scale ◽  
Design Stage ◽  
Flow Profile ◽  
Expected Return ◽  
Tidal Turbines ◽  
Theoretical Predictions ◽  
Tidal Turbine

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively over-engineer the device at additional cost. Both of these scenarios have consequences on the expected return from the project. Despite an extensive amount of research on the mechanical loading of model scale tidal turbines, very little is known from full-scale devices operating in real sea conditions. This paper addresses this by reporting on the rotor loads measured on a 400 kW tidal turbine. The results obtained during ebb tidal conditions were found to agree well with theoretical predictions of rotor loading, but the measurements during flood were lower than expected. This is believed to be due to a disturbance in the approaching flood flow created by the turbine frame geometry, and, to a lesser extent, the non-typical vertical flow profile during this tidal phase. These findings outline the necessity to quantify the characteristics of the turbulent flows at sea sites during the entire tidal cycle to ensure the long-term integrity of the deployed tidal turbines.

Phosphorus removal by apatite in horizontal flow constructed wetlands for small communities: pilot and full-scale evidence

2011 ◽  
Vol 63 (8) ◽  
pp. 1629-1637 ◽  
Author(s):  
N. Harouiya ◽  
S. Martin Rue ◽  
S. Prost-Boucle ◽  
A. Liénar ◽  
D. Esser ◽  
...  
Keyword(s):  
Constructed Wetlands ◽  
Particle Surface ◽  
Full Scale ◽  
Retention Capacity ◽  
Small Communities ◽  
Lab Experiments ◽  
Apatite Mineral ◽  
Kinetics Of ◽  
P Removal

Phosphorus (P) removals in constructed wetlands (CWs) have received particular attention in recent decades by using specific materials which promote adsorption/precipitation mechanisms. Recent studies have shown interest in using apatite materials to promote P precipitation onto the particle surface. As previous trials were mainly done by lab experiments, this present study aims to evaluate the real potential of apatites to remove P from wastewater in pilot units and a full-scale plant over a 2 year period. P retention kinetics of two qualities of apatites are presented and discussed. In this work apatite appears to have high retention capacity (>80% of P removal) and is still an interesting way for P removal in CWs for limiting the risk of eutrophication downstream of small communities. Nevertheless, the apatite quality appears to be of great importance for a reliable and long term P removal. The use of materials with low content of apatite mineral (40–50%) seems to be not economically relevant.

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