Guidelines on the Numerical Detern1ination of Stress Concentration Factors of Tubular Joints

2004 ◽  
pp. 640-640
Keyword(s):  
Stress Concentration ◽  
Tubular Joints ◽  
Concentration Factors ◽  
Stress Concentration Factors

Stress Concentration Factors Calculation: Analytical and Numerical Approaches for Welded Tubular Joints

2020 ◽  
Author(s):  
Nathalia Paruolo ◽  
Thalita Mello ◽  
Paula Teixeira ◽  
Marco Pérez
Keyword(s):  
Stress Concentration ◽  
Oil And Gas ◽  
Hot Spot ◽  
Experimental Tests ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Gas Industry ◽  
Tubular Joints ◽  
Concentration Factors ◽  
Stress Concentration Factors

Abstract In the oil and gas industry, fixed platforms are commonly applied in shallow water production. In-place environmental conditions generates cyclic loads on the structure that might lead to structural degradation due to fatigue damage. Fatigue is one of the most common failure modes of offshore structures and is typically estimated when dimensioning of the structure during design phase. However, in times when life extension of existing offshore structures is being a topic in high demand by industry, mature fields may represent an interesting investment, especially for small companies. Concerning fixed platforms, composed mainly by welded tubular joints, the assessment of hot spot stresses is considered to predict structure fatigue. The estimation of welded joint hot spot stresses is based on the stress concentration factors (SCFs), which are given by parametric formulae, finite element analysis (FEA) or experimental tests. Parametric formulae may be defined as a fast and low-cost method, meanwhile finite elements analysis may be time consuming and experimental tests associated with higher costs. Given these different characteristics, each method is applied according to the study case, which will rely on the joint geometry and associated loads. Considering simple joint geometries several sets of parametric equations found in the literature may be applied. On the other hand, the SCFs calculation of non-studied yet complex joints consider known formulae adapted according to the under load joint behavior and geometry. Previous analysis shows that this adaptation may furnish different results compared to those obtained by FEA. Furthermore, it is observed that even for simple joints the results derived from the different methods may differ. Given their importance for the oil and gas industry, since they are the basis for the assessment of the fatigue life of welded tubular joints which may impact on additional costs related to maintenance and inspection campaigns, the estimation of SCFs must be the most accurate as possible. Therefore, this paper intends to investigate the differences between results derived from parametric formulae and different FEA studies.

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.

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 Concentration Factors of DK Square-to-Square Tubular Joints

1995 ◽  
Vol 117 (4) ◽  
pp. 265-275 ◽  
Author(s):  
A.-K. Soh ◽  
C.-K. Soh
Keyword(s):  
Stress Concentration ◽  
American Petroleum Institute ◽  
Axial Loads ◽  
Classification Approach ◽  
Tubular Joints ◽  
Out Of Plane ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Element Technique ◽  
Joint Classification

The fatigue life of tubular joints with many braces, e.g., DK and DTK joints, are commonly determined by treating them as tubular joints with less braces, e.g., T/Y, K, and X joints, based on the joint classification approach recommended by the American Petroleum Institute. The DK square-to-square tubular joint type was selected to verify the reliability and accuracy of such an approach. A parametric stress analysis of DK square-to-square tubular joints subjected to axial loads, in-plane and out-of-plane bending moments has been performed using the finite element technique. The results of this analysis are presented as a set of formulas 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 DK square-to-square tubular joints and those obtained for X and K square-to-square tubular joints, which are commonly employed to simulate the former when the joint classification approach is adopted. In general, the stress concentration factors for DK joints are significantly higher, which shows that the recommended approach may not be reliable and accurate in dealing with DK joints.

Stress Concentration Factors in T and K-T Tubular Joints Using Finite Element Analysis

1988 ◽  
Vol 110 (4) ◽  
pp. 246-254 ◽  
Author(s):  
O. D. Dijkstra ◽  
R. S. Puthli ◽  
H. H. Snijder
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Axial Load ◽  
Bending Moment ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Tubular Joints ◽  
Tubular Joint ◽  
Concentration Factors ◽  
Stress Concentration Factors

Stress concentration factors (SCFs) in a T and a K-T tubular joint have been determined using the finite element method (FEM). The SCFs are determined for basic load cases (axial load or bending moment) in one of the braces or in the chord. The results of the FEM are compared with available experimental data and with parametric formulas. The T-joint results for brace loadings agree reasonably with the parametric formulas. The K-T joint results for in-plane bending agree reasonably with the parametric formulas.

Computation of Stress Concentration Factors for Tubular Joints

2013 ◽  
Author(s):  
Philippe Thibaux ◽  
Steven Cooreman
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Tubular Joints ◽  
Element Size ◽  
Out Of Plane ◽  
Weld Toe ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Bending Modes

Stress concentration factors for tubular joints were computed using solid quadratic elements. The results of the computations are compared with experiments reported in the literature and with expressions reported in the literature and in design codes. An influence of element size and element type was observed, which leads to recommendations regarding element size of four quadratic elements in thickness, which is finer than in different published recommendations. A parametric study was performed, showing that stress concentration factors from the literature are not always conservative, particularly at the crown toe of the chord, while they tend to be overconservative at the chord saddle. The stress concentration factor for the inside of the member was also computed; it is found that it can be close to the stress concentration factor at the weld toe for both the in plane or out of plane bending modes.

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