Hull Structural Analysis of Turret-Moored FPSOs Considering Hull–Turret Interaction

2014 ◽  
Author(s):  
Ki-Myung Lee ◽  
Won-Hyuk Choi ◽  
Hyun Soo Kim ◽  
Seung Han Moon ◽  
Jin Tae Kim
Keyword(s):  
Structural Analysis ◽  
Adaptive Design ◽  
Design Procedure ◽  
Contact Problems ◽  
Direct Analysis ◽  
Offshore Structures ◽  
Linear Superposition ◽  
Strength Assessment ◽  
Hull Structure ◽  
Set Up

For turret-moored ship-type offshore structures such as floating production storage and offloading (FPSO) units, the hull structure is affected by mooring and riser loads that are transferred through turret systems, in addition to environmental loads on the hull itself. Moreover, the existence of turret structures has an influence on the structural behavior of the hull around the turret system. In the structural design of FPSOs, the turret structure and its loads are considered in a direct analysis of hull structure for a realistic strength assessment of FPSOs. This paper investigates several specific techniques for hull structural analysis considering the interaction with the turret system. The linear gap function is utilized to represent the nonlinear contact behavior between the hull and turret structures. The linear superposition of structural responses is also adapted, and its validity is demonstrated in the case of hull–turret contact problems. These studies conclude that the hull structures with turret systems that involve contact nonlinearity in their interface can be assessed using the conventional hull strength assessment based on linear analysis. Moreover, by including the turret model directly in hull structural analysis, the uncertainty arising from hull–turret interface loads can be reduced, and a robust and adaptive design procedure can be set up in the detailed engineering stages.

scholarly journals Corrosion of Steel Rebars in Anoxic Environments. Part II: Pit Growth Rate and Mechanical Strength

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2547
Author(s):  
Elena Garcia ◽  
Julio Torres ◽  
Nuria Rebolledo ◽  
Raul Arrabal ◽  
Javier Sanchez
Keyword(s):  
Mechanical Strength ◽  
Chloride Content ◽  
Element Model ◽  
Offshore Structures ◽  
Anoxic Environments ◽  
Electrochemical Parameters ◽  
Cathode Area ◽  
Optical Profilometer ◽  
Set Up ◽  
Corrosion Of Steel

Reinforced concrete may corrode in anoxic environments such as offshore structures. Under such conditions the reinforcement fails to passivate completely, irrespective of chloride content, and the corrosion taking place locally induces the growth of discrete pits. This study characterised such pits and simulated their growth from experimentally determined electrochemical parameters. Pit morphology was assessed with an optical profilometer. A finite element model was developed to simulate pit growth based on electrochemical parameters for different cathode areas. The model was able to predict long-term pit growth by deformed geometry set up. Simulations showed that pit growth-related corrosion tends to maximise as cathode area declines, which lower the pitting factor. The mechanical strength developed by the passive and prestressed rebar throughout its service life was also estimated. Passive rebar strength may drop by nearly 20% over 100 years, whilst in the presence of cracking from the base of the pit steel strength may decline by over 40%.

Effect of Air Fraction on Force Coefficients in Oscillatory Flow

2021 ◽  
Author(s):  
Malene Hovgaard Vested ◽  
Erik Damgaard Christensen
Keyword(s):  
High Speed ◽  
Offshore Structures ◽  
Air Injection ◽  
Wave Loads ◽  
Morison Equation ◽  
Force Coefficients ◽  
Air Content ◽  
Set Up ◽  
High Level ◽  
Spilling Breakers

Abstract The forces on marine and offshore structures are often affected by spilling breakers. The spilling breaker is characterized by a roller of mixed air and water with a forward speed approximately equal to the wave celerity. This high speed in the top of the wave has the potential to induce high wave loads on upper parts of the structures. This study analyzed the effect of the air content on the forces. The analyses used the Morison equation to examine the effect of the percentage of air on the forces. An experimental set-up was developed to include the injection of air into an otherwise calm water body. The air-injection did introduce a high level a turbulence. It was possible to assess the amount of air content in the water for different amounts of air-injection. In the mixture of air and water the force on an oscillating square cylinder was measured for different levels of air-content, — also in the case without air. The measurements indicated that force coefficients for clear water could be use in the Morison equation as long as the density for water was replaced by the density for the mixture of air and water.

Numerical Investigation of Ultimate Strength of Stiffened Plates With Various Cross-Section Forms

2018 ◽  
Author(s):  
Huilong Ren ◽  
Yifu Liu ◽  
Chenfeng Li ◽  
Xin Zhang ◽  
Zhaonian Wu
Keyword(s):  
Aluminum Alloy ◽  
Ultimate Strength ◽  
Cross Section ◽  
High Performance ◽  
Lightweight Design ◽  
Offshore Structures ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Element Analysis ◽  
Hull Structure

There is an increasing interest in the lightweight design of ship and offshore structures, more specifically, choosing aluminum alloys or other lightweight high-performance materials to build structure components and ship equipments. Due to its better mechanical properties and easy assembly nature, extruded aluminum alloy stiffened plates are widely used in hull structures. When the load on the hull reaches a certain level during sailing, partial or overall instability of stiffened plate makes significant contribution in an event of collapse of the hull structure. It is very necessary to investigate the ultimate strength of aluminum alloy stiffened plate to ensure the ultimate bearing capacity of large aluminum alloy hull structure. Most of studies of the ultimate strength of stiffened plates deal with stiffened plates with T–shaped stiffeners. Stiffeners of other shapes have seldom been explored. In this research, the ultimate strength of six different cross–section aluminum alloy stiffened plates and one steel stiffened plate was studied based on the non–linear finite element analysis (FEA). Taking into account stiffness, weight and other issues, the new cross–section aluminum stiffener has finally been concluded for replacing the original steel stiffener in upper deck of a warship.

scholarly journals Design & Weight Optimization of a Wheel Rim for Sport Utility Vehicle.

2018 ◽  
Vol 172 ◽  
pp. 03006
Author(s):  
Harish Panjagala ◽  
Balakrishna M ◽  
Shasikant Kushnoore ◽  
E L N Rohit Madhukar
Keyword(s):  
Structural Analysis ◽  
Point Of View ◽  
Weight Optimization ◽  
Strength Assessment ◽  
Suitable Material ◽  
The Road ◽  
Wheel Rim ◽  
Standard Values ◽  
Design Weight ◽  
Structural Point

Automobile have various parts which are important for good running of the vehicle. The most important safety components from a structural point of view are the road wheels. They are required to be lighter and more fascinating to the buyer all the time. This implies that it's important to perform a lot of accurate strength assessment on wheel styles. The wheel rim plays a major role in vehicle dynamics. This paper deals with the design and model of different wheel rims based on weight optimization and also structural analysis has been carried out. It has been compared with standard values by varying two different materials. In addition, from the obtained outputs of simulations and the weight optimization, we suggested Aluminium alloys as most suitable material for SUV. Model is created by using SOLIDWORKS software 2015 and structural analysis &; weight optimization is done by using ANSYS WORKBENCH 16.0.

Structural Analysis of a Gas Turbine Axial Compressor Blade Eroded by Online Water Washing

2020 ◽  
Author(s):  
Rossella Cinelli ◽  
Gianluca Maggiani ◽  
Serena Gabriele ◽  
Alessio Castorrini ◽  
Giuliano Agati ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Gas Turbine ◽  
Axial Compressor ◽  
Compressor Blades ◽  
Performance Levels ◽  
Water Washing ◽  
Critical Issues ◽  
Air Intake ◽  
Set Up ◽  
The Impact

Abstract The Gas Turbine (GT) Axial Compressor (AXCO) can absorb up to the 30% of the power produced by the GT, being the component with the largest impact over the performances. The axial compressor blades might undergo the fouling phenomena as a consequence of the unwanted material locally accumulating during the machine operations. The presence of such polluting substances reduces the aerodynamic efficiency as well as the air intake causing the drop of performances and the increase of the fuel consumption. To address the above-mentioned critical issues, several washing strategies have been implemented so far, among the most promising ones, High Flow On-Line Water Washing (HFOLWW) is worth to mention. Exploiting this technique, the performance levels are preserved, whereas the stops for maintenance should be reduced. Nevertheless, this comes at the cost of a long-term erosion exposure caused by the impact of water washing droplets. Hence, it was deemed necessary to carry out a finite element method (FEM) structural analysis of the first rotor stage of the compressor of an aeroderivative GT, integrated into the HFOLWW scheme, in order to evaluate the fatigue strength of the component subjected to the erosion; possibly along with its acceptability limits. The first step requires the determination of the blade areas affected by erosion, using computational fluid dynamics (CFD) simulations, followed by the creation and the 3D modelling of the damaged geometry. The final step consists in the evaluation of the static stress and the dynamic agents, to perform a fatigue analysis through the Goodman relation and carrying out a simulation of damage propagation exploiting the theory of fracture mechanics. This procedure has been extended to the damage-free baseline component to set-up a model suitable for comparison. The structural analysis confirms the design of the blade, moreover dynamic and static evaluation of the eroded profiles haven’t outlined any working, nor mechanical, issue. This entitles the structural choice of HFOLWW as a system which guarantees full performance levels of the compressor.

Very Large Floating Structures

2007 ◽  
Author(s):  
H. Suzuki ◽  
H. R. Riggs ◽  
M. Fujikubo ◽  
T. A. Shugar ◽  
H. Seto ◽  
...  
Keyword(s):  
Design Procedure ◽  
Offshore Structures ◽  
Floating Structure ◽  
Floating Structures ◽  
Design Procedures ◽  
Novel Technology ◽  
Hydroelastic Analysis ◽  
Behavior Design ◽  
Hydroelastic Response ◽  
Near Future

Very Large Floating Structure (VLFS) is a unique concept of ocean structures primary because of their unprecedented length, displacement cost and associated hydroelastic response. International Ship and Offshore Structures Congress (ISSC) had paid attention to the emerging novel technology and launched Special Task Committee to investigate the state of the art in the technology. This paper summarizes the activities of the committee. A brief overview of VLFS is given first for readers new to the subject. History, application and uniqueness with regard to engineering implication are presented. The Mobile Offshore Base (MOB) and Mega-Float, which are typical VLFS projects that have been investigated in detail and are aimed to be realized in the near future, are introduced. Uniqueness of VLFS, such as differences in behavior of VLFS from conventional ships and offshore structures, are described. The engineering challenges associated with behavior, design procedure, environment, and the structural analysis of VLFS are introduced. A comparative study of hydroelastic analysis tools that were independently developed for MOB and Mega-Float is made in terms of accuracy of global behavior. The effect of structural modeling on the accuracy of stress analysis is also discussed. VLFS entails innovative design methods and procedure. Development of design criteria and design procedures are described and application of reliability-based approaches are documented and discussed.

scholarly journals An Optimized Table-Top Small-Angle X-ray Scattering Set-up for the Nanoscale Structural Analysis of Soft Matter

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
T. Sibillano ◽  
L. De Caro ◽  
D. Altamura ◽  
D. Siliqi ◽  
M. Ramella ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Small Angle ◽  
Soft Matter ◽  
X Ray ◽  
X Ray Scattering ◽  
Set Up ◽  
Ray Scattering

Assessment of Fatigue Damage of Floating Fish Cages Due to Wave Induced Response

2009 ◽  
Author(s):  
Paul E. Thomassen ◽  
Bernt J. Leira
Keyword(s):  
Structural Analysis ◽  
Fatigue Damage ◽  
Design Procedure ◽  
Irregular Waves ◽  
Induced Response ◽  
Fish Farms ◽  
Analysis And Design ◽  
Drag Forces ◽  
Fatigue Design ◽  
Fish Cages

Floating fish cages provide the main production utilities for salmon farming. However, despite their pivotal role in production safety as well as in protection of the environment, there is still much room for improvement in relation to verified structural design procedures and computerized tools for structural analysis. To a large extent they can be regarded as not being in accordance with the state-of-the-art of structural analysis and design for more traditional types of marine structures. In this paper a study of fatigue design for floating fish farms is presented. The study is based on a structure which is being applied by the Norwegian fish farming industry today. The floater is made of steel cylinders which are configured as a square. The formulation for the wave loading is based on a combination of potential theory and horizontal drag forces on the floater. Horizontal and vertical drag forces on the netpen are also accounted for. A fatigue design procedure for floating fish farms in steel is suggested. The procedure is based on a time domain analysis of the structure in irregular waves. For each seastate half an hour (real time) analysis is performed and the stress history for an assumed critical location is computed. Based on the stress histories, the fatigue damage is estimated by application of rain flow counting and a given SN curve. The scatter diagram for the seastates at a given location is generated from the associated wind speed distribution.

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