Calculation of the stress concentration factor in the welded tube junction subjected to combined loadings

2014 ◽  
Vol 11 (4) ◽  
pp. 339-348 ◽  
Author(s):  
A. Fouathia ◽  
A. Mekroud ◽  
K. Bellagh
Keyword(s):  
Stress Concentration ◽  
Fatigue Failure ◽  
Hot Spots ◽  
Combined Loading ◽  
Stress Concentrations ◽  
Tubular Joints ◽  
Out Of Plane ◽  
Welded Tube ◽  
Plane Bending ◽  
Shore Platforms

Fatigue failure caused by stress concentrations in tubular welded joints is observed in off shore platforms subjected to cyclic loading in corrosive marine environments. In some junctions, the stress concentration can induce a stress thirty times the nominal stress, and increase the risk of fatigue failure in tubular joints. Therefore, it is necessary to accurately assess the intensity of the stress concentrations to effectively deal with the problem of fatigue damage and lead to reliable tubular joints. This work aims to study the stress distribution and location of the "hot" spots in a Twelded tubular structure subjected to a combined loading of tension and bending (in-plane bending, out of plane bending and traction) to better simulate the actual loading.

Stress Concentrations in DT/X Square-to-Square and Square-to-Round Tubular Joints

1994 ◽  
Vol 116 (2) ◽  
pp. 49-55 ◽  
Author(s):  
A. K. Soh ◽  
C. K. Soh
Keyword(s):  
Stress Concentration ◽  
Bending Moment ◽  
Bending Moments ◽  
Axial Loads ◽  
Stress Concentrations ◽  
Tubular Joints ◽  
Out Of Plane ◽  
Concentration Factors ◽  
Plane Bending ◽  
Stress Concentration Factors

A parametric stress analysis of DT/X square-to-square and square-to-round tubular joints subjected to axial loads, in-plane, and out-of-plane bending moments has been performed using the finite element technique in order to provide a sound basis for using such sections in the design of complex structures. The results of this analysis are presented as a set of equations expressing the stress concentration factor as a function of the relevant geometric parameters for various loading conditions. A comparison is made between the results obtained for square-to-square and square-to-round tubular joints and those obtained for round-to-round tubular joints by other researchers. In general, the stress concentration factors for square-to-square tubular joints are the highest, followed by those of the corresponding round-to-round joints, with those of the corresponding square-to-round joints the lowest when the joints are subject to axial loads. In the case of in-plane bending moment, the stress concentration factors for square-to-square joints are generally still the highest, but followed by those of the corresponding square-to-round joints, with those of the corresponding round-to-round joints the lowest. However, the stress concentration factors for the three types of joint are comparable when they are subject to out-of-plane bending moments.

Stress Concentrations in T/Y and K Square-to-Square and Square-to-Round Tubular Joints

1992 ◽  
Vol 114 (3) ◽  
pp. 220-230 ◽  
Author(s):  
A. K. Soh ◽  
C. K. Soh
Keyword(s):  
Stress Concentration ◽  
Bending Moments ◽  
Axial Loads ◽  
Stress Concentrations ◽  
Tubular Joints ◽  
Out Of Plane ◽  
Concentration Factors ◽  
Plane Bending ◽  
Stress Concentration Factors ◽  
Element Technique

A parametric stress analysis of T/Y and K square-to-square and square-to-round tubular joints subjected to axial loads, in-plane and out-of-plane bending moments has been performed using the finite element technique in order to provide a sound basis for using such sections in the design of complex structures. The results of this analysis are presented as a set of 42 equations expressing the stress concentration factor as a function of the relevant geometric parameters for various loading conditions. A comparison is made between the results obtained for square-to-square and square-to-round tubular joints and those obtained for round-to-round tubular joints by other researchers. In general, the stress concentration factors obtained from round-to-round and square-to-round tubular joints are closer as compared with those of the corresponding square-to-square tubular joints. Moreover, the stress concentration factors for square-to-square tubular joints are generally lower than those of the corresponding round-to-round and square-to-round tubular joints when the joints are subject to axial loads; but the reverse is true when the joints are subject to in-plane bending moments. However, the stress concentration factors for the three types of joint are comparable when they are subject to out-of-plane bending moments.

scholarly journals The Influence of Longitudinal Stiffeners on Weld Toe Stress Concentrations in Multi Planar Tubular KK Joints

2007 ◽  
Vol 348-349 ◽  
pp. 409-412
Author(s):  
Charles O. Woghiren ◽  
F.P. Brennan
Keyword(s):  
Stress Concentration ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Stress Concentrations ◽  
Out Of Plane ◽  
Invaluable Tool ◽  
Weld Toe ◽  
Dimensional Parameters ◽  
Stress Concentration Factors ◽  
Jack Up

This paper reports a parametric stress analysis of various configurations of rack plate stiffened multi-planar welded KK joints using the finite element method. The KK joint finds application in the leg structure of offshore Oil & Gas jack-up platforms. The rack plate is a dual purpose element of the joint because it firstly functions as a stiffener which reduces the stress concentration at the brace/chord intersection. This could be an immense contribution to the increase in fatigue life of the joint but other hot spot sites are introduced to the joint. The rack is also used for raising and lowering of the jack-up hull which gives the jack-up platform its jacking capability. Over 120 models using a combination of shell and solid elements were built and analysed within ABAQUS. Non-dimensional joint geometric parameters; β, γ and . were employed in the study with . being defined as the ratio of rack thickness to chord diameter. Stress Concentration Factors (SCFs) were calculated under applied axial and OPB (out-of-plane-bending) loading. Three critical SCF locations were identified for each load case, with each location becoming the most critical based on the combination of the non-dimensional parameters selected for the joint. This is important as careful design can shift the critical SCF from an area inaccessible to NDT to one that can be easily inspected. The SCF values extracted from the models were used to derive six parametric equations through multiple regression analysis performed using MINITAB. The equations describe the SCF at the different locations as a function of the non-dimensional ratios. The equations not only allow the rapid optimisation of multi-planar joints but also can be used to quickly identify the location of maximum stress concentration and hence the likely position of fatigue cracks. This in itself is an invaluable tool for planning NDT procedures and schedules.

Probabilistic analysis of stress concentration factors in unstiffened gap tubular KT-joints of jacket structures under the out-of-plane bending moment loads

2016 ◽  
Vol 20 (4) ◽  
pp. 595-615 ◽  
Author(s):  
Hamid Ahmadi ◽  
Mir Amin Mousavi Nezhad Benam
Keyword(s):  
Stress Concentration ◽  
Probability Density ◽  
Bending Moment ◽  
Probability Density Functions ◽  
Density Functions ◽  
Out Of Plane ◽  
Jacket Structures ◽  
Concentration Factors ◽  
Plane Bending ◽  
Stress Concentration Factors

The stress concentration factor, which is one of the primary input parameters for the fatigue reliability analysis of tubular joints commonly found in offshore jacket structures, shows substantial scatter that highlights the importance of accurate derivation of its governing probability function. In this article, results of 144 finite element stress analyses, validated using experimental data, were used to derive the probability density functions for the stress concentration factors in unstiffened gap tubular KT-joints under four types of out-of-plane bending moment loadings. Based on a parametric finite element study, a sample database was prepared for the maximum chord-side stress concentration factors of central and outer braces, and density histograms were generated for these samples. Nine different probability density functions were fitted to these histograms. The maximum likelihood method was used to estimate the parameters of fitted distributions. In each case, Kolmogorov–Smirnov test was applied to assess the goodness-of-fit. Finally, the inverse Gaussian model was selected as the best-fitted distribution, and after substituting the values of estimated parameters, six fully defined probability density functions were proposed for the maximum chord-side stress concentration factors of central and outer braces in unstiffened gap KT-joints under four types of out-of-plane bending loading.

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