TN X SN Fatigue Curves for KS Hook and Chain Using Finite Elements Modelling and Model Test

2007 ◽  
Author(s):  
Jose´ Carlos Lima de Almeida ◽  
Ronaldo Rosa Rossi ◽  
Ricardo Sobral
Keyword(s):  
Finite Elements ◽  
Model Test ◽  
Fatigue Curve ◽  
Functional Condition ◽  
Mooring Line ◽  
Hardness Profile ◽  
Mooring Lines ◽  
Finite Elements Modeling ◽  
Predicting Behavior ◽  
Finite Elements Modelling

The new scenario of oil exploration in ultra deep water moves forward to 3000 m, has been putting for the companies that accept this technological challenger significant, border of the techno-scientific knowledge. Therefore, nowadays in this case of ultra deep waters, where the forces above the mooring lines are increase and the use of the new material in Petrobras Floating Production Units, it is necessary the good numerical analyses and experimental test by the mooring line. It appears the need to look for a solution for the problems according to the changes of the polyester rope in the production platform without the bottom extension change and its foundation (fixed point). According to this challenge it was necessary to develop a remote connection and disconnection device. This device is the KS hook and its optimization has been created using the fracture mechanical conception optics and computers tools (FEM and mooring software). There are two conditions to develop this device: one condition is functional and the other is structural. For the functional condition, it’s necessary to create the facilities for handling and installations. For the structural conditions, it is necessary to use the special wrought steel material, treatment for steel characteristic and right geometry. Finite Elements Modeling analyze used the Ansys software, considered the hardness profile material for Minimum Break Load (MBL). The lifetime design is about 25 years for this case and the fatigue analysis considered the residual stress and plasticity for structural device. Previous simulation is especially important in predicting behavior and in the development of new design products before testing. The model was meshed with 3D first order tetrahedral elements solid45. The mesh was sufficiently fine to ensure minimal loss of accuracy in curved geometry. There isn’t a TN fatigue curve (reference API Fatigue curves) for this KS Hook device geometry, in this case become necessary to use the model test to obtain this curve with the extrapolation of the results. The Finite Elements Modeling analyze used with the Material SN Fatigue curve will be used for this validation. Previous simulation is especially important in predicting behavior and in the development of new design products before testing.

scholarly journals Experimental Study on Development of Mooring Simulator for Multi Floating Cranes

2021 ◽  
Vol 9 (3) ◽  
pp. 344
Author(s):  
Junhyeok Bae ◽  
Juhwan Cha ◽  
Min-Guk Seo ◽  
Kangsu Lee ◽  
Jaeyong Lee ◽  
...  
Keyword(s):  
Model Test ◽  
Equations Of Motion ◽  
Mooring Line ◽  
Analysis Program ◽  
The Finite Element Method ◽  
Mooring Lines ◽  
Calculation Results ◽  
Floating Crane ◽  
Pile Model ◽  
Equations Of Motions

In this study, the coupled motion of a mooring system and multifloating cranes were analyzed. For the motion analysis, the combined equations of motions of the mooring line and multifloating cranes were introduced. The multibody equations for floating cranes were derived from the equations of motion. The finite element method (FEM) was used to derive equations to solve the stretchable catenary problem of the mooring line. To verify the function of mooring simulator, calculation results were compared with commercial mooring software. To validate the analysis results, we conducted an experimental test for offshore operation using two floating crane models scaled to 1:40. Two floating crane models and a pile model were established for operation of uprighting flare towers. During the model test, the motion of the floating cranes and tensions of the mooring lines were measured. Through the model test, the accuracy of the mooring analysis program developed in this study was verified. Therefore, if this mooring analysis program is used, it will be possible to perform a mooring analysis simulation at the same time as a maritime work simulation.

Experimental Validation of a Numerical Model for a Dry-Tree Semisubmersible in Benign Environments

2014 ◽  
Author(s):  
Bruce Martin ◽  
Oriol Rijken ◽  
Kent Davies
Keyword(s):  
Model Test ◽  
Nonlinear Behavior ◽  
Primary Objective ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Test Configuration ◽  
Numerical Tools ◽  
Offshore Industry ◽  
Heave Motion

The offshore industry has spent the last several years developing semisubmersible platforms capable of supporting both drilling and production activities. The production trees are located on top of the top tensioned risers (TTRs) on a Dry Tree Semisubmersible. A key challenge in the design of these vessels is to reduce the heave motion as much as possible to enable the use of state-of-the-art riser tensioners. A model test campaign was executed as part of the developmental program. The primary objective of this campaign was to improve the accuracy of the numerical tools to be used in the design process. Riser tensioners are typically hydro-pneumatic devices, with a nonlinear tension-stroke relationship. A riser tensioner was developed at model scale which had a similar nonlinear behavior to the prototype. Examining the effect of this tensioner on the global motions was an additional objective of this test campaign. The techniques used to model this nonlinear spring is described, and its effect on global motions investigated. A key challenge in model testing platforms intended for ultra-deep water (e.g. greater than 7000 ft) is the modeling of the mooring and riser system. The premise for the design of the model mooring system is 1.) maintain as best as possible the force-offset relationship of the mooring lines and 2.) be able to describe the model test configuration in the numerical tools to be used for global design. The near taut behavior of the prototype mooring system is modeled using heavy chain and a high-catenary mooring line.

A Novel Hybrid Method of Pre-Tension Adjustment of Mooring Lines in the Model Test

2020 ◽  
Author(s):  
Junfeng Du ◽  
Hongchao Wang ◽  
Anteng Chang ◽  
Mingyuan Sun ◽  
Junrong Wang ◽  
...  
Keyword(s):  
Model Test ◽  
Line Tension ◽  
Line Length ◽  
Mooring Line ◽  
Cyclic Process ◽  
Mooring System ◽  
Ideal Model ◽  
Mooring Lines ◽  
Target Value ◽  
The Ideal

Abstract Mooring lines are the most commonly used station-keeping systems for floating platforms, and the pre-tension of the mooring lines has significant effect on the dynamics of floater/mooring system. However, during the model test, which is the most important method for the research on the floater/mooring system, the pre-tension of the designed mooring lines in the basin are always significantly different with the target values of the ideal model due to the error of the manufacture of the mooring lines and positon locating of the anchor point and so on. As a result, the adjustment of the pretension of the mooring lines based on the ideal model is an important task during the model test. The pre-tension is always adjusted by increasing or decreasing mooring line length. While all the mooring lines are connected with the floater and coupled with each other, pre-tension adjustment is an unwarranted and cyclic process which often wastes a lot of time. This paper presents a novel methodology for regulating the mooring line pre-tension based on matrix calculation. The increment matrix of the mooring line tension can be obtained by increasing or decreasing the length of each mooring line in the numerical model. Assuming that the increment the mooring line tension is linear to the change of the mooring line length, the adjustment amount of each mooring line length can be calculated from the difference of the real pre-tension and the target pre-tension. However, the mooring line tension is always nonlinear to the mooring line length. Calculating the increment matrix of the mooring line tension and adjustment of the mooring line length is also a cyclic process until the error of real pre-tension of the model in the basin and target value can meet the accuracy requirement. This method is used in a model of a mooring system with 12 mooring lines which are connected with a semi-submersible platform. The test results show that the pre-tension of mooring lines can be adjusted to the target value quickly based on the method proposed in this paper.

scholarly journals Transient Responses Evaluation of FPSO with Different Failure Scenarios of Mooring Lines

2021 ◽  
Vol 9 (2) ◽  
pp. 103
Author(s):  
Dongsheng Qiao ◽  
Binbin Li ◽  
Jun Yan ◽  
Yu Qin ◽  
Haizhi Liang ◽  
...  
Keyword(s):  
Service Condition ◽  
Mooring Line ◽  
Mooring System ◽  
Transient Effects ◽  
Floating Platform ◽  
Transient Responses ◽  
Mooring Lines ◽  
Performance Deterioration ◽  
Steady State Responses ◽  
Influence Process

During the long-term service condition, the mooring line of the deep-water floating platform may fail due to various reasons, such as overloading caused by an accidental condition or performance deterioration. Therefore, the safety performance under the transient responses process should be evaluated in advance, during the design phase. A series of time-domain numerical simulations for evaluating the performance changes of a Floating Production Storage and Offloading (FPSO) with different broken modes of mooring lines was carried out. The broken conditions include the single mooring line or two mooring lines failure under ipsilateral, opposite, and adjacent sides. The resulting transient and following steady-state responses of the vessel and the mooring line tensions were analyzed, and the corresponding influence mechanism was investigated. The accidental failure of a single or two mooring lines changes the watch circle of the vessel and the tension redistribution of the remaining mooring lines. The results indicated that the failure of mooring lines mainly influences the responses of sway, surge, and yaw, and the change rule is closely related to the stiffness and symmetry of the mooring system. The simulation results could give a profound understanding of the transient-effects influence process of mooring line failure, and the suggestions are given to account for the transient effects in the design of the mooring system.

Experimental Investigation vs Numerical Simulation of the Dynamic Response of a Moored Floating Structure to Waves

2014 ◽  
Author(s):  
Daniele Dessi ◽  
Sara Siniscalchi Minna
Keyword(s):  
Dynamical Behavior ◽  
Irregular Waves ◽  
Mooring Line ◽  
Floating Structure ◽  
Mooring Lines ◽  
Wave Energy Converters ◽  
Time Histories ◽  
Actual Configuration ◽  
Proper Orthogonal ◽  
Dynamic Wave

A combined numerical/theoretical investigation of a moored floating structure response to incoming waves is presented. The floating structure consists of three bodies, equipped with fenders, joined by elastic cables. The system is also moored to the seabed with eight mooring lines. This corresponds to an actual configuration of a floating structure used as a multipurpose platform for hosting wind-turbines, aquaculture farms or wave-energy converters. The dynamic wave response is investigated with numerical simulations in regular and irregular waves, showing a good agreement with experiments in terms of time histories of pitch, heave and surge motions as well as of the mooring line forces. To highlight the dynamical behavior of this complex configuration, the proper orthogonal decomposition is used for extracting the principal modes by which the moored structure oscillates in waves giving further insights about the way waves excites the structure.

Optimized Mooring Line Simulation Using a Hybrid Method Time Domain Scheme

2014 ◽  
Author(s):  
Niels Hørbye Christiansen ◽  
Per Erlend Torbergsen Voie ◽  
Jan Høgsberg ◽  
Nils Sødahl
Keyword(s):  
Hybrid Method ◽  
Time Domain ◽  
Computation Time ◽  
Mooring Line ◽  
Mooring Lines ◽  
Fem Model ◽  
Input Variables ◽  
The Time Domain ◽  
The Cost ◽  
Short Time

Dynamic analyses of slender marine structures are computationally expensive. Recently it has been shown how a hybrid method which combines FEM models and artificial neural networks (ANN) can be used to reduce the computation time spend on the time domain simulations associated with fatigue analysis of mooring lines by two orders of magnitude. The present study shows how an ANN trained to perform nonlinear dynamic response simulation can be optimized using a method known as optimal brain damage (OBD) and thereby be used to rank the importance of all analysis input. Both the training and the optimization of the ANN are based on one short time domain simulation sequence generated by a FEM model of the structure. This means that it is possible to evaluate the importance of input parameters based on this single simulation only. The method is tested on a numerical model of mooring lines on a floating off-shore installation. It is shown that it is possible to estimate the cost of ignoring one or more input variables in an analysis.

Finite elements modeling of olive tree mechanical harvesting using different shakers

Trees ◽  
2013 ◽  
Vol 27 (6) ◽  
pp. 1537-1545 ◽  
Author(s):  
H. Bentaher ◽  
M. Haddar ◽  
T. Fakhfakh ◽  
A. Mâalej
Keyword(s):  
Finite Elements ◽  
Olive Tree ◽  
Finite Elements Modeling

The Anchor-Last Deployment Problem for Inextensible Mooring Lines

1975 ◽  
Vol 97 (3) ◽  
pp. 1046-1052 ◽  
Author(s):  
Robert C. Rupe ◽  
Robert W. Thresher
Keyword(s):  
Numerical Model ◽  
Equations Of Motion ◽  
Simultaneous Equations ◽  
Mooring Line ◽  
Integration Scheme ◽  
Lumped Mass ◽  
Mooring Lines ◽  
Concentrated Masses ◽  
Predictor Corrector ◽  
Lagrange’S Method

A lumped mass numerical model was developed which predicts the dynamic response of an inextensible mooring line during anchor-last deployment. The mooring line was modeled as a series of concentrated masses connected by massless inextensible links. A set of angles was used for displacement coordinates, and Lagrange’s Method was used to derive the equations of motion. The resulting formulation exhibited inertia coupling, which, for the predictor-corrector integration scheme used, required the solution of a set of linear simultaneous equations to determine the acceleration of each lumped mass. For the selected cases studied the results show that the maximum tension in the cable during deployment will not exceed twice the weight of the cable and anchor in water.

Validation of Mooring Simulations (for Mooring Integrity Assessment) With In-Service Tension Measurements

2021 ◽  
Author(s):  
Willemijn Pauw ◽  
Remco Hageman ◽  
Joris van den Berg ◽  
Pieter Aalberts ◽  
Hironori Yamaji ◽  
...  
Keyword(s):  
Numerical Models ◽  
Weather Conditions ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Data Set ◽  
Integrity Assessment ◽  
Motion Data ◽  
Load Cells ◽  
Line Loads

Abstract Integrity of mooring system is of high importance in the offshore industry. In-service assessment of loads in the mooring lines is however very challenging. Direct monitoring of mooring line loads through load cells or inclinometers requires subsea installation work and continuous data transmission. Other solutions based on GPS and motion monitoring have been presented as solutions to overcome these limitations [1]. Monitoring solutions based on GPS and motion data provide good practical benefits, because monitoring can be conducted from accessible area. The procedure relies on accurate numerical models to model the relation between global motions and response of the mooring system. In this paper, validation of this monitoring approach for a single unit will be presented. The unit under consideration is a turret-moored unit operating in Australia. In-service measurements of motions, GPS and line tensions are available. A numerical time-domain model of the mooring system was created. This model was used to simulate mooring line tensions due to measured FPSO motions. Using the measured unit response avoids the uncertainty resulting from a prediction of the hydrodynamic response. Measurements from load cells in various mooring lines are available. These measurements were compared against the results obtained from the simulations for validation of the approach. Three different periods, comprising a total of five weeks of data, were examined in more detail. Two periods are mild weather conditions with different dominant wave directions. The third period features heavy weather conditions. In this paper, the data set and numerical model are presented. A comparison between the measured and numerically calculated mooring line forces will be presented. Differences between the calculated and measured forces are examined. This validation study has shown that in-service monitoring of mooring line loads through GPS and motion data provides a new opportunity for mooring integrity assessment with reduced monitoring system complexity.

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