Distribution of weld toe stress concentration factors on the central brace in two-planar CHS DKT-connections of steel offshore structures

2011 ◽  
Vol 49 (10) ◽  
pp. 1225-1236 ◽  
Author(s):  
Hamid Ahmadi ◽  
Mohammad Ali Lotfollahi-Yaghin ◽  
Mohammad H. Aminfar
Keyword(s):  
Stress Concentration ◽  
Offshore Structures ◽  
Weld Toe ◽  
Concentration Factors ◽  
Stress Concentration Factors

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 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.

Alternate Design Solutions for Reduced Stress Concentration Factor (SCF) T Joints of Circular Hollow Structures

2014 ◽  
Vol 1029 ◽  
pp. 44-49
Author(s):  
Gabriel Dima ◽  
Teodor Machedon-Pisu ◽  
Ion Balcu
Keyword(s):  
Stress Concentration ◽  
Analytical Calculation ◽  
Tubular Structures ◽  
Element Analysis ◽  
Hollow Structures ◽  
Development Teams ◽  
Practical Design ◽  
Weld Toe ◽  
Concentration Factors ◽  
Stress Concentration Factors

Design for fatigue of lightweight welded tubular structures is a significant concern of development teams. Based on practical design experience, alternate T joint design to usual Circular Hollow Structures (CHS) T joins are proposed. Proposed designs employ formed members within relevant dimensions range. A method based on finite element analysis including weld modelling was used, with analytical calculation of weld toe stress. Stress concentration factors (SCF) are calculated for all proposed designs for all typical load cases. Best placement and dimensions of formed members is given, together with design recommendations.

Stress Distribution Formulas and Comparison of Three Stress Analysis Techniques for Tubular Joints

1985 ◽  
Vol 107 (1) ◽  
pp. 60-67
Author(s):  
S. Dharmavasan ◽  
W. D. Dover
Keyword(s):  
Stress Concentration ◽  
Stress Analysis ◽  
Mixed Mode ◽  
Hot Spot ◽  
Offshore Structures ◽  
Hot Spot Stress ◽  
Analysis Techniques ◽  
Mode Stress ◽  
Concentration Factors ◽  
Stress Concentration Factors

The available data on hot spot stress for tubular welded joints has been reviewed and a database established. Stress analysis techniques in general use for the design of offshore structures and parametric equations have been assessed against this database to determine their accuracy. A set of equations to predict the stress distributions for simple joints has been proposed and has been used to predict mixed mode stress concentration factors. Results obtained from a complex K joint have been examined in detail and the importance of the stress state, when predicting the mixed mode stress concentration factors, is demonstrated.

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.

Stress Concentration Factors at Welded Connections Between Tubular Sections and a Transverse Plate

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Inge Lotsberg
Keyword(s):  
Stress Concentration ◽  
Wind Turbines ◽  
Oil And Gas ◽  
Superposition Principle ◽  
Gas Production ◽  
Oil And Gas Production ◽  
Weld Toe ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Weld Root

Abstract Welded connections between tubulars and transverse plates are used to build together part structures such as support of flare towers and wind turbines and deck structures on foundation structures. They are used in traditional jacket structures for oil and gas production and in support structures for wind turbines. These welded connections are typically made from the outside resulting in a weld root on the inside and a weld toe on the outside. Different S–N curves apply to these positions; therefore, stresses both on the inside and the outside are needed for fatigue assessment. From the actual design, it is noted that the thicknesses of the tubulars being connected can be different. Also, the diameters of the tubulars can be different. In addition, the fabrication is associated with some fabrication tolerances that provide local eccentricity moments to be transferred through these connections. In this paper, analytical expressions for stress concentration factors for these connections are presented based on classical shell theory. The stress concentration is dependent on the radial restraint from the transverse plate and the eccentricity of the neutral axes in the tubular thickness of one tubular relative to the other tubular. The superposition principle is used to derive resulting stress concentration factors for the inside weld root and the outside weld toe.

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