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quadratic plate of similar size with rounded comers. The stress concentration factor increases with the
size of the doubling plates.
2.3.6 Hopper knuckle

The effect of fabrication tolerances for a hopper knuckle was investigated in analyses performed by
Lloyd's Register, see Figure 6. The analysis results are presented by Polezhaeva and Chung (2001). A
load case with motion induced pressure acting inside the ballast tank was analysed. Based on this
analyses it was found that a nominal eccentricity of 0.25 t would result in the lowest stress
concentration factor and the longest fatigue life.
2.3.7 Experiencefiomjnite element analyses of the full scale tests

All the full scale test specimens were analysed by shell elements. (Bureau Veri-, Umoe and DNV
performed these analyses). In general there is a very good correspondence between these analyses and
the measured stress for specimens 3-5. There is less good correspondence for specimen I. It is
observed that it is difficult to model the connection between the bulb and the buckling stiffener
including brackets properly by use of shell elements only. Specimen 4 was also analysed by three-
dimensional finite elements and there is a very good correspondence with the measured stress, see
Figure 7. Some selected analysis results are presented by Rucho et al. (2001).

3 EXTENSION OF THE PROJECT

A number of participants have shown interest in planning an extension of the project (Phase 11).
An extension of the project is planned to contain:
9 Further work to achieve a reliable link between calculated stress from FE analyses and S-N data for
fatigue cracks initiating 6rom weld toes and from the roots of fillet welds that is numerical accurate,
robust and efficient to use by engineers.
9 Further fatigue testing to achieve S-N data for other typical FPSO details that can be used for
calibration of analysis technology.
9 Verification of analysis procedure on full scale test specimens tested in Phase I.
9 Methodology for fatigue assessment of the transverse structure of FPSOs. This includes
determination of local pressure around the mean water leve1, linearised frequency analyses for wet and
dry areas (non-linear problem), and fatigue testing of capacity of connections subjected to pressure
loading.
P Procedure for inspection and repair of fatigue cracks in FPSOs on the field.
An extension is planned carried out in the time period 2001-2003.

References
Chen W. and Landet E. (2001). Stress Analysis of Cut-outs with and without Reinforcement. OMAE
Rio ddaneiro.
Doc. No. FFC-S910-RP-O002/Rev. C SCFs for Topside Support Stools. Bluewater 2000.
DNV (2000) Recommended Practice Rp - C203 Fatigue Strength Analysis of Offshore Structures.
Fricke W. (2001). Recommended Hot Spot Analysis Procedure for Structural Details of FPSO's and
Ships Based on Round-Robin FE Analyses. ISOPE Stavanger.
Hobbacher A. (1996). Fatigue Design of Welded Joints and Components. IIW. XIII-1539-96/ XV-845-
96.
HSE (1995). Guidance on Design, Constmction and Certification.
Kim, W. S. (2000). Fatigue Test of Typical Weld Joints. Hyundai Heavy Industries Co., Ltd.