Fatigue Evaluation of Offshore Steel Structures Considering Stress Concentration Factor

The installation of offshore structures and facilities in the marine environment, usually for the production and transmission of oil, gas exploration, electricity, and other natural resources is referred to as offshore construction. Since offshore structures are subjected to changing threats to the environment year-round. Fatigue behavior prediction noticed on these structures should be considered during the design stage. Fatigue is one of the failure mechanisms of offshore steel structures, and it must be investigated properly during system design. The fatigue analysis of offshore structures under drag wave force, total wave force, total moment about the sea bed, and other variables are reviewed thoroughly. The structure's dynamic response becomes a critical aspect in the whole design process. The fatigue analysis was carried out using MATLAB software, material properties of the offshore structure, and wave spectrum characteristics in this study. This study shows the JONSWAP spectrum and stress concentration analysis prediction. The offshore support structure that is predicted during the design phase will help to keep the stress concentration factor below the fatigue threshold and anticipate safe life design, according to the results of the fatigue study. The fatigue performances of tripod and jacket steel support structures in intermediate waters depth are compared in this project (20-50 m). The North Atlantic Ocean is used as a reference site, with a sea depth of 45 meters. The tripod and jacket support structures will be designed by using current industry standards. Keywords: [Fatigue evaluation, North Atlantic Ocean and Failure].

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Mechanical Properties on the Welded Connection of Pipe and Hollow Spheres Joints

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.3452 ◽

2011 ◽

Vol 189-193 ◽

pp. 3452-3457

Author(s):

Ya Jie Yan ◽

Hong Gang Lei ◽

Xue Yang

Keyword(s):

Finite Element ◽

Stress Concentration ◽

Stress Distribution ◽

Wall Thickness ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Hollow Spheres ◽

Steel Structures ◽

Element Analysis ◽

Static Tests

Taking pipe - hollow spherical node as the object, and using ANSYS finite element analysis software, established five kinds of finite element model to analyze the stress concentration at the weld connection of the different connections of steel structures - hollow ball under the uniaxial tension. Obtained this node’s stress concentration factor, stress distribution, by changing the hollow spherical diameter and wall thickness, pipe’s diameter and wall thickness, obtained the trend of the stress concentration factor under different control ball matches. Take static tests on typical structures of two specifications 6 hollow sphere nodes, get the measured stress concentration factor, and stress distribution of this node. Through comparative analysis of theoretical analysis and experimental results, show that the two rules are consistent. The research results can provide basis for improving the pipe - hollow spherical joints connecting structural.

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Experimental studies to determine strain concentration factors for space tubular joints

The Journal of Strain Analysis for Engineering Design ◽

10.1243/03093247v224237 ◽

1987 ◽

Vol 22 (4) ◽

pp. 237-245 ◽

Cited By ~ 1

Author(s):

R Sundaravadivelu ◽

C G Nandakumar ◽

S K Srivastava ◽

C Ganapathy

Keyword(s):

Stress Concentration ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Experimental Studies ◽

Offshore Structures ◽

Strain Concentration ◽

Tubular Joints ◽

Orthogonal Plane ◽

Concentration Factors ◽

Semi Empirical

This paper presents studies carried out on grouted and ungrouted space tubular joints, with K in one plane and T in the orthogonal plane. Three models have been tested for different load cases adopting T, K, and both T and K (STK) configurations. The tubular joints used in offshore structures, especially in jacket platforms, are multiplanar and some are grouted and hence their study is essential. The stress concentration factor, SCF, as determined using the semi-empirical formulae which are applicable for planar joints are not appropriate for space, grouted joints. The results of the present study indicates that the SCF as determined by formulae for simple joints is unsafe in the plane of K and conservative in the plane of T for the space joint. The effect of the grout is to reduce the stress concentration.

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Computation of stress concentration factor of tubular joints for the fatigue analysis of steel structures

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1114/1/012009 ◽

2021 ◽

Vol 1114 (1) ◽

pp. 012009

Author(s):

M Althaf ◽

K Muhammed Navvar ◽

Gowtham Prakash ◽

Noel Varghese ◽

C A Navaneeth

Keyword(s):

Stress Concentration ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Steel Structures ◽

Fatigue Analysis ◽

Tubular Joints

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Stress Concentration Factor of A Two-Planar Double KT Tubular Joint due to In-Plane Bending Loading in Steel Offshore Structures

MATEC Web of Conferences ◽

10.1051/matecconf/201817701006 ◽

2018 ◽

Vol 177 ◽

pp. 01006

Author(s):

Prastianto Rudi Walujo ◽

Hadiwidodo Yoyok Setyo ◽

Fuadi Ibnu Fasyin

Keyword(s):

Finite Element ◽

Stress Concentration ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Element Model ◽

Offshore Structures ◽

Geometrical Parameters ◽

Offshore Structure ◽

Wide Range ◽

Tubular Joint

The purpose of this study is to investigate the proper Stress Concentration Factor (SCF) of a 60° two-planar DKT tubular joint of a tripod wellhead offshore structure. So far, calculation of SCF for a multi-plane tubular joint was based on the formulation for the simple/uniplanar tubular joints that yield in over/under prediction of the SCF of the joint. This situation in turn decreasing the accuracy of fatigue life prediction of the structures. The SCF is one of the most important parameters in the tubular joint fatigue analysis. The tubular joint is modelled as finite element models with bending loads acting on the braces that cover a wide range of dimensionless geometrical parameters (β, τ, γ). The effect of such parameters on the SCF distribution along the weld toe of braces and chord on the joint are investigated. Validation of the finite element model has shown good agreement to the global structural analysis results. The results of parametric studies show that the peak SCF mostly occurs at around crown 2 point of the outer central brace. The increase of the β leads to decrease the SCF. While the increase of the τ and γ leads to increase the SCF. The effect of parameter β and γ on the SCF are greater than the effect of parameter τ.

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Study of Typical Welded Joint Hot Spot Stress Concentration Factor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.160-162.1482 ◽

2010 ◽

Vol 160-162 ◽

pp. 1482-1487

Author(s):

Bin Jie Wang ◽

Qiang Li ◽

Zhi Ming Liu

Keyword(s):

Stress Concentration ◽

Stress Concentration Factor ◽

Concentration Factor ◽

High Speed ◽

Welded Joint ◽

Hot Spot ◽

Nominal Stress ◽

Hot Spot Stress ◽

The Difference ◽

Fatigue Evaluation

Hot spot stress (HSS) approach is more applicable for fatigue evaluation, because it is more closer to the real stress at the welded notch than nominal stress.This paper studies a typical welded joint, fillet welded joint, which is used widely in high-speed car. Hot spot stress concentration factor is calculated under different nominal stress and loading methods. The S-N curves belong to nominal stress and hot spot stress were analysized. The result show that the difference between the S-N curves under different load style can be reduced greatly by hot spot stress. The hot spot stress characteristic variable was put forward, which is used to describe the influence from the welding size of the joint.

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