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Journal ArticleDOI

Development of parametric equations for ultimate capacity of internally ring-stiffened tubular T/Y-joints under axial and moment load

TL;DR: Tubular joints in offshore structures are designed using semi-empirical equations developed based on experimental and numerical studies as discussed by the authors, and same were recommend for use in API-RP-2A and other c...
Abstract: Tubular joints in offshore structures is being designed using semi-empirical equations developed based on experimental and numerical studies and same were recommend for use in API-RP-2A and other c...
Citations
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20 Sep 1993
TL;DR: In this article, the authors present an approach for the analysis and design of tubular structures, based on the A.W.S. code, and propose new rules for tubular connections.
Abstract: 1. Introduction to Tubular Structures. Attributes of Tubes. Architectural and Structural Forms. The Need for an Integrated Approach. Author's Viewpoint for this Monograph. Tubulars as Structural Members. Simple Welded Joints. 2. Conceptual Basis for the Design Rules. Definitions. Failure modes of tubular connections. General procedures for analysis and design. Design simplifications. Stresses in welds. 3. Static Strength of Circular Section Joints. Early work on T-, Y-, and K-connections. Lessons from field failures. Overcoming the beta paradox. Empirical punching shear design equation. Understanding the sources of reserve strength. Further evolution of the A.W.S. code. Final form. Design charts. 4. Fatigue Design. Levels of analysis. Hot spot stress. Stress concentration factors (SCF). S-N curves. Comparisons with international rules and data. 5. Tubular Connections Involving Non-Circular Sections. Box connections - existing A.W.S. rules. Box connections - proposed new rules. Hybrid connections. Special topics. Fatigue box connections. 6. Special Topics for Circular Section Joints. Overlapping connections. Multi-planar connections. Grouted connections. Internally stiffened tubular connections. 7. Fatigue Size and Profile Effects. Fracture toughness. Lamellar tearing. Role of redundancy. Non-destructive inspection criteria. 8. Construction System. Material selection. Tube manufacture. Connection layout. Welded joint design. Welder and procedure qualification. Prefabrication. Assembly. Inspection. Appendices. 1. Symbols and notation. 2. Design revisions, tubular structures. 3. Notch toughness task group, proposed revisions for AWS D1.1. Index.

66 citations

Journal ArticleDOI
TL;DR: In this paper , the results of performing 324 FE analyses on 108 circular hollow section (CHS) X-connections with fiber reinforced polymer (FRP) have been used to derive a probability distribution model for SCFs in the retrofitted joints under axial, IPB, and OPB loads.

5 citations

DOI
17 Oct 2022
TL;DR: In this article , an alternate approach of elemental and cyclical time discretized method is proposed for more realistic fatigue life estimations, which can instrument in avoiding fatigue life underestimation (uneconomic) or overestimation (structural failure).
Abstract: Wave induced hydrodynamic loads among various environmental loads hold prominence while designing offshore structures. The cyclic and non-linear character of such loads eventually generates structural fatigue leading to failure, terming the span as fatigue life. The instances of attaining members’ maximum load substantially differ than the instance of structural global load maxima as represented by aggregating loads on members in traditional method of fatigue life analysis. This paper recommends an alternate approach of elemental and cyclical time discretized method owing to more realistic fatigue life estimations. A MATLAB programme has been developed comprising of wave phase angles and instances corresponding to maximum hydrodynamic load on each member, structural redistributive analysis considering quasi-statics, joint configuration recognition, parametric SCF assessments (globally accepted semi-empirical standard explicit equations), and interpreting SN curves for steel tubular joints (API RP 2A 21st Ed. - WJ), evaluating cumulative damage by Miner’s rule and estimating fatigue life of the joints’ interfaces. The proposed analysis has been simulated using a numerical model example, enabling a better understanding of significant prediction differences than of the conventional method. Its applicability in offshore industry could instrument in avoiding fatigue life underestimation (uneconomic) or overestimation (structural failure) lead towards safe and economic designs.
References
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Journal ArticleDOI
TL;DR: In this paper, an incremental approach to the solution of buckling and snapping problems is explored, where the authors use the length of the equilibrium path as a control parameter, together with the second order iteration method of Newton.

1,821 citations


"Development of parametric equations..." refers methods in this paper

  • ...The numerical procedure is adopted by Modified Riks method (Riks 1979) to monitor the post-peak load shedding behaviour....

    [...]

Proceedings ArticleDOI
01 Jan 1980
TL;DR: In this paper, a total of 137 ultimate strength tests on simple T,Y,DT and K tubular joints are used as a basis for development of new ultimate capacity formulas and the accuracy of these formulas is then studied in a statistical manner.
Abstract: A total of 137 ultimate strength tests on simple T,Y,DT and K tubular joints is used as a basis for development of new ultimate capacity formulas. The data are taken from a variety of sources and only relatively large geometries are considered. Axial tension, axial compression, in-plane bending and out-of plane bending loads are represented. The failure condition is taken as the minimum of either maximum load, first crack load or load at an excessive deformation limit. Several formulas are recommended to predict the capacity of the different joint and load types. The accuracy of these formulas is then studied in a statistical manner. Predictions of past and present API RP 2A formulas are compared to the same data base. It is found that the new equations are more consistent in their level of prediction and result in less scatter. The new equations are also relatively simple in format.

96 citations


"Development of parametric equations..." refers background or methods in this paper

  • ...The ultimate axial and moment capacity was calculated based on the deformation and rotation limit proposed by Yura et al. (1980)....

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  • ...So the ultimate moment capacity could be selected based on the rotation limit (θyura) proposed by Yura et al. (1980)....

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  • ...For those cases, the ultimate axial capacity can be assessed by the deformation limit (δyura) proposed by Yura et al. (1980) which is widely used in the offshore design code of API (2014) and calculated by Equation (2). dyura = 60Fybd E (2) In cases, where the load-displacement relationship do not…...

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  • ...So the ultimate moment capacity could be selected based on the rotation limit (θyura) proposed by Yura et al. (1980). The rotation limit at the brace end as calculated by Equation (3),...

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  • ...However, the crack initiation could not be ascertained in the numerical model and hence the ultimate axial capacity is based on the deformation limit proposed by Yura et al. (1980)....

    [...]

20 Sep 1993
TL;DR: In this article, the authors present an approach for the analysis and design of tubular structures, based on the A.W.S. code, and propose new rules for tubular connections.
Abstract: 1. Introduction to Tubular Structures. Attributes of Tubes. Architectural and Structural Forms. The Need for an Integrated Approach. Author's Viewpoint for this Monograph. Tubulars as Structural Members. Simple Welded Joints. 2. Conceptual Basis for the Design Rules. Definitions. Failure modes of tubular connections. General procedures for analysis and design. Design simplifications. Stresses in welds. 3. Static Strength of Circular Section Joints. Early work on T-, Y-, and K-connections. Lessons from field failures. Overcoming the beta paradox. Empirical punching shear design equation. Understanding the sources of reserve strength. Further evolution of the A.W.S. code. Final form. Design charts. 4. Fatigue Design. Levels of analysis. Hot spot stress. Stress concentration factors (SCF). S-N curves. Comparisons with international rules and data. 5. Tubular Connections Involving Non-Circular Sections. Box connections - existing A.W.S. rules. Box connections - proposed new rules. Hybrid connections. Special topics. Fatigue box connections. 6. Special Topics for Circular Section Joints. Overlapping connections. Multi-planar connections. Grouted connections. Internally stiffened tubular connections. 7. Fatigue Size and Profile Effects. Fracture toughness. Lamellar tearing. Role of redundancy. Non-destructive inspection criteria. 8. Construction System. Material selection. Tube manufacture. Connection layout. Welded joint design. Welder and procedure qualification. Prefabrication. Assembly. Inspection. Appendices. 1. Symbols and notation. 2. Design revisions, tubular structures. 3. Notch toughness task group, proposed revisions for AWS D1.1. Index.

66 citations


"Development of parametric equations..." refers methods in this paper

  • ...The recommendation adopted in the 3rd edition was based on the punching shear concept as proposed by Marshall (1992) and subsequently adopted by American Welding Society (AWS D 1.1 2015)....

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  • ...…specimens with single ring-stiffener located at the saddle position under axial compressive load and it was observed that the capacity increases by 50–150% and the unstiffened and stiffened joint and used cut and try method (Marshall 1992) for calculating the capacity of the stiffened joint....

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Journal ArticleDOI
TL;DR: In this article, the effect of geometrical parameters on the chord-side stress concentration factors (SCFs) along the weld toe of the intersection between the outer (inclined) brace and the chord in internally ring-stiffened tubular KT-joints subjected to balanced axial loads was investigated.

64 citations


"Development of parametric equations..." refers background in this paper

  • ...…ring-stiffeners (Nassiraei et al. 2016; Nassiraei et al. 2016a, 2016b, 2016d; Nassiraei et al. 2016c; Nassiraei et al. 2017) to reduce the stresses (Ahmadi et al. 2012; Ahmadi et al. 2013, 2015; Ahmadi and Zavvar 2015; Ahmadi 2016; Nassiraei et al. 2019) though unstiffened joints are preferred for…...

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  • ...2017) to reduce the stresses (Ahmadi et al. 2012; Ahmadi et al. 2013, 2015; Ahmadi and Zavvar 2015; Ahmadi 2016; Nassiraei et al. 2019) though unstiffened joints are preferred for fabrication....

    [...]

Journal ArticleDOI
TL;DR: In this article, a finite element study on tubular DT-joints with internal ring stiffeners subjected to axial brace compression is presented. And a theoretical model based on the observed failure mechanism in the stiffener is then presented, with a postulated six-hinge collapse mechanism.

61 citations


"Development of parametric equations..." refers methods in this paper

  • ...An upper bound solution was proposed based on theoretical model of six hinge failure mechanism (Lee and Llewelyn-Parry 2005)....

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Trending Questions (1)
How is the displacement limit (3%d) determined to determine the ultimate capacity of tubular joints?

The paper does not provide information on how the displacement limit is determined for determining the ultimate capacity of tubular joints.