Internal ring-stiffeners do not significantly affect the ductility of tubular joints as stiffened joints reach their peak strengths at about the same deformation level as their unstiffened counterparts
Strength of ring-stiffened tubular T-joints in offshore structures—
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, no. 3 (1999): 239.0-264
Although not commonly used in modern design, ring-stiffeners were extensively used to enhance the strength of tubular joints found in older offshore steel jacket structures. No detailed guidance on the determination of strength of ring-stiffened joints can be found in any major offshore code. There is therefore a need for research for the...更多
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- Tubular joints in circular hollow sections are major structural components in offshore jacket structures.
- None of the major offshore design codes, such as API  and HSE , provides any substantial quantitative recommendations on static strength requirements.
- This is due partly to the vast variety of possible stiffening arrangements and partly to the dearth of information avail-
- Tubular joints in circular hollow sections are major structural components in offshore jacket structures
- Guidance on strength estimation is still needed for the purposes of structural assessment of older platforms and it is estimated that there are at least 2000 ring-stiffened joints in the North Sea alone 
- For the stiffened joint R-1-1, Table 2 shows that changing the number of rings of elements down the depth of the stiffener has no noticeable effect on strength
- A database of some 40 stiffened joints has been generated from the numerical study
- Internal ring-stiffeners do not significantly affect the ductility of tubular joints as stiffened joints reach their peak strengths at about the same deformation level as their unstiffened counterparts
- The joint ratios ␤ and ␥ have a significant influence on the strength enhancement provided by the stiffeners
- Results of convergence and validation study
The results of the convergence study for the unstiffened joint R-0-2, shown in Table 1, illustrate that convergence was more or less achieved with a mesh density of 1452 elements, as a significant increase in the number of elements to 1808, mesh R-0-2/5, which more than doubled the cpu time required for analysis, produced almost no change in strength.
- The load–displacement history for each analysis, stiffened or unstiffened, was plotted and the strength of the joints, as well as the stiffeners, were determined from these plots.
- A database of some 40 stiffened joints has been generated from the numerical study.
- The numerical procedure can provide accurate and valid strength predictions of both unstiffened and stiffened T-joints.
- 3. The development of discrete plastic zones in the stiffeners suggests that they fail by the formation of plastic hinges from bending, rather than fail by shear yielding.
- 4. The joint ratios ␤ and ␥ have a significant influence on the strength enhancement provided by the stiffeners
- Table1: Results of convergence study for unstiffened joint R-0-2
- Table2: Results of convergence study for stiffened joint R-1-1
- Table3: Results of validation study
- Table4: Notation for stiffened joint reference
- Table5: Details of joints/stiffeners for investigating the influence of tw and dw
- Table6: Details of joints/stiffeners for investigating the influence of tf
- Table7: Details of joints/stiffeners for investigating the influence of bf
- Table8: Details of joint/stiffeners for investigation the influence of ␤
- Table9: Details of joint/stiffeners for investigation the influence of ␥
- Table10: Comparison of joints with single, double and triple stiffeners
- Financial support from both the University of Wales Swansea and MSL Engineering are gratefully acknowledged
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