The Research on the Fatigue Analysis of the Jack-Up’s Leg Based on SESAM Software

2015 ◽  
Author(s):  
Zeng Ji ◽  
Yuan Hongtao ◽  
Wang Chao ◽  
Wang Yuhan ◽  
Mo Jian
Keyword(s):  
Wave Direction ◽  
Dynamic Amplification Factor ◽  
Design Life ◽  
Force Transfer ◽  
Drilling Unit ◽  
Concentration Factors ◽  
Cumulative Fatigue Damage ◽  
Dynamic Amplification ◽  
Stress Concentration Factors ◽  
Jack Up

In this paper, a fatigue assessment based on spectrum analysis for Jack-up’s legs is performed by adopting stochastic method for three water depths using DNV/SESAM. Firstly, force transfer function is determined by the DNV/WAJAC for each wave direction considered. Secondly, members end stresses are computed by the DNV/SESTRA. Then SCF (stress concentration factors), DAF (dynamic amplification factor) and P-delat effects are applied in the stress range calculations. Finally, the cumulative fatigue damage of unidirectional waves to the critical connections is determined by the DNV/FRAMEWORK. The critical connections at the chords and the braces are selected and reviewed for fatigue life calculation. The results show that the legs have fatigue lives exceeding the expected design life of Jack-Up Drilling Unit of twenty-five (25) years and meet ABS requirement.

A Multidimensional FEA Approach for Determination of Hot Spot Stresses in Offshore Jacket Structures

2021 ◽  
Author(s):  
Kris Hectors ◽  
Hasan Saeed ◽  
Wim De Waele
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Hot Spot ◽  
Wave Spectrum ◽  
Wave Direction ◽  
Tubular Joints ◽  
Jacket Structures ◽  
Concentration Factors ◽  
Stress Concentration Factors

Abstract A new fatigue lifetime assessment approach for offshore jacket structures is presented. It combines a previously developed numerical framework for automated determination of stress concentration factors in tubular joints and a multidimensional finite element modelling approach. The approach is explained based on a case study of an OC4 type offshore jacket. To determine the fatigue life, a directional wave spectrum is combined with the JONSWAP spectrum. The fatigue life of the jacket is assessed for two different sea states. Based on the fatigue analysis the most fatigue critical wave direction is identified. The hot spot stresses in one of the most critical joints are determined and compared to stresses obtained with the Efthymiou equations. The shortcomings of these equations are highlighted and it is shown how the numerical framework can be used to improve the current fatigue design philosophy for offshore jackets which relies on the Efthymiou equations for stress concentration factors in the welded tubular joints.

A Generic Study on Lowering Analysis of Massive Jumper Structures

2015 ◽  
Author(s):  
Guomin Sun ◽  
Facheng Wang ◽  
Yigong Zhang ◽  
Ke Tang ◽  
Jun Wang
Keyword(s):  
Environmental Parameters ◽  
Wire Rope ◽  
Wave Direction ◽  
Dynamic Amplification Factor ◽  
Natural Period ◽  
Target Field ◽  
Lift Capacity ◽  
Engineering Company ◽  
Advanced Analysis ◽  
Dynamic Amplification

Lifting activity has been usually employed to deploy subsea equipment, especially for huge structures. In one target field of China South Sea, there was one 3D “M” shaped, long and massive jumper being lowered to 200 meter water depth. The jumper was nearly 90 meters long, 22 inches in diameter, deployed by using a spreader frame. The total weight of jumper and frame has been up to nearly 400 Te in air. The whole lifting system mainly includes spreader frame, jumper, two connectors, wire rope and serial slings, etc. Two connectors were welded on both ends of the jumper, and jumper was lifted under spreader by several slings. The deployment operation was proposed by deepwater pipelay crane vessel Hai Yang Shi You (HYSY) 201. To ensure a successful installation, COTEC Offshore Solutions, together with its mother company, China Offshore Oil Engineering Company, have developed an advanced analysis by considering practical offshore field procedure and accurate modeling technology. In this paper, firstly, wet lift capacity of wire rope and natural period of the hosting system have been obtained for certain circumstances including axial resonance caused by hostile environment. In addition, lowering though the splash zone operation procedure was simulated by OrcaFlex 9.8a. Allowable Max crane tip tension force, Dynamic Amplification Factor (DAF), Min wire rope force, Max Cranemaster® stroke motion and heave velocity at jumper were obtained during the numerical analysis. Also, allowable values of these key factors are further studied. According to the above analysis, COTEC provides a series of environmental parameters such as the optimum wave direction and period for the offshore lifting operation.

scholarly journals Stress Concentration Factors for Welded Plate T-Joints Subjected to Tensile, Bending and Shearing Loads

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 546
Author(s):  
Krzysztof L. Molski ◽  
Piotr Tarasiuk
Keyword(s):  
Stress Concentration ◽  
Plate Thickness ◽  
Percentage Error ◽  
Geometrical Parameters ◽  
T Joints ◽  
Loading Mode ◽  
Weld Toe ◽  
Concentration Factors ◽  
Parametric Expression ◽  
Stress Concentration Factors

The paper deals with the problem of stress concentration at the weld toe of a plate T-joint subjected to axial, bending, and shearing loading modes. Theoretical stress concentration factors were obtained from numerical simulations using the finite element method for several thousand geometrical cases, where five of the most important geometrical parameters of the joint were considered to be independent variables. For each loading mode—axial, bending, and shearing—highly accurate closed form parametric expression has been derived with a maximum percentage error lower than 2% with respect to the numerical values. Validity of each approximating formula covers the range of dimensional proportions of welded plate T-joints used in engineering applications. Two limiting cases are also included in the solutions—when the weld toe radius tends to zero and the main plate thickness becomes infinite.

Stress Analysis of Holes in Thick Plates

2004 ◽  
Vol 1-2 ◽  
pp. 153-158 ◽  
Author(s):  
S. Quinn ◽  
Janice M. Dulieu-Barton
Keyword(s):  
Stress Concentration ◽  
Stress Analysis ◽  
Uniaxial Tension ◽  
Plane Stress ◽  
Plate Surface ◽  
Flat Plates ◽  
Thick Plates ◽  
Concentration Factors ◽  
Stress Concentration Factors

A review of the Stress Concentration Factors (SCFs) obtained from normal and oblique holes in thick flat plates loaded in uniaxial tension has been conducted. The review focuses on values from the plate surface and discusses the ramifications of making a plane stress assumption.

Stress concentration factors for the torsion of curved beams of arbitrary cross-section

2006 ◽  
Vol 220 (12) ◽  
pp. 1709-1726 ◽  
Author(s):  
R E Cornwell
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Cross Section ◽  
Cross Sections ◽  
Shear Stresses ◽  
Curved Beams ◽  
Finite Element Implementation ◽  
Out Of Plane ◽  
Concentration Factors ◽  
Stress Concentration Factors

There are numerous situations in machine component design in which curved beams with cross-sections of arbitrary geometry are loaded in the plane of curvature, i.e. in flexure. However, there is little guidance in the technical literature concerning how the shear stresses resulting from out-of-plane loading of these same components are effected by the component's curvature. The current literature on out-of-plane loading of curved members relates almost exclusively to the circular and rectangular cross-sections used in springs. This article extends the range of applicability of stress concentration factors for curved beams with circular and rectangular cross-sections and greatly expands the types of cross-sections for which stress concentration factors are available. Wahl's stress concentration factor for circular cross-sections, usually assumed only valid for spring indices above 3.0, is shown to be applicable for spring indices as low as 1.2. The theory applicable to the torsion of curved beams and its finite-element implementation are outlined. Results developed using the finite-element implementation agree with previously available data for circular and rectangular cross-sections while providing stress concentration factors for a wider variety of cross-section geometries and spring indices.

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