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  1. Crannog

    Weight per inch table for standard welds ?

    If you want a ball-park figure I've found 5% of total structural-steel weight to usually be about right, but that is dependent on fabrication type. On a low welding application I would use 5% to capture weld + paint. If you have prior history of this type of fab you can keep and eye on how much...
  2. Crannog

    Alloy 625 - Norsok M-001

    A quick look on Google has: http://www.diva-portal.org/smash/get/diva2:746556/FULLTEXT01.pdf http://www.twi-global.com/technical-knowledge/published-papers/resistance-of-dissimilar-joints-between-steel-and-nickel-alloys-to-hydrogen-assisted-cracking-march-2008/ Not sure if it's relevant but...
  3. Crannog

    Alloy 625 - Norsok M-001

    I don't know a lot about subsea-HISC outside of steels but typically it is driven by: Exposure to hydrogen, from CP system Loading, residual (eg from welding) or external to material (eg pressure, mass, etc) Hardness Yield/Proof value I'm not sure about the 30°C maximum value, it seems a bit...
  4. Crannog

    Selection of FEA package for offshore structures (Oil & Gas)

    I'm not trying to teach you to suck eggs but I'll give a pretty low-level/general reply: Ansys and Abacus are common enough in the industry, and there are plenty of Ansys users in the Aberdeen area. Typically both their sales reps will tell you both can do the job and both are probably right. At...
  5. Crannog

    [QUESTION] Offshore structure H beam CODE check practice

    Easy answer for this one, yes. There are significant differences between rolled and built H's for fatigue. Having a look through Appendix A of DNV RP-C203 (or similar) will tell you a lot of what you need to know. Disregarding the geometry differences the addition of welds (and weld defects)...
  6. Crannog

    Definition of Knockdown Factor (KDF)

    Never used one but some quick googling shows: http://scholar.lib.vt.edu/theses/available/etd-101198-161441/unrestricted/ch1.pdf http://www.sciencedirect.com/science/article/pii/S002076831000051X It sounds like an empirical method for reducing 'best-case' calculated values to match...
  7. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    True, but the explicit definition of the membrane stress for an axial load (or global bending) is exclusive of the tubular geometry, hence that σ.x remains but σ.y isn't used (instead σ.h is used for the the hoop stress). C201 maintains the σ.xSd terminology but inconveniently doesn't define the...
  8. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    If it's a help RP-C202 defines membrane stress (σ.x) as: σ.x.Sd = σ.a.Sd + σ.m.Sd Where: σ.a.Sd = design membrane stress in the longitudinal direction due to uniform axial force σ.m.Sd = design membrane stress in the longitudinal direction due to global bending D
  9. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    I don't see many cases where global σ.membrane + σ.bending are going to be lower than membrane on it's own? And those that are (eg axial tension & compressive bending and visa versa) would be clear to identify from your loadcase? So long as the sign for your stresses is the same then total...
  10. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    I think the intent of this notation is that σ.x & σ.y contain the global bending induced stresses (i.e. hull bending) but not those from in-plate-thickness effects (such as lateral loading from hydrostatic pressure), that would be checked separately (Section 5). How you approach them would...
  11. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    Typically the FEA equivalent stress would be conservative as it will include σ.x σ.y & σ.z, inclusive of bending. So long as you inside the allowable your design doesn't have any issues unless you are trying to squeeze some additional capacity out of it? Depending on the geometry your only...
  12. Crannog

    DNV - Yield Check Allowable Values - How to include plate bending stress?

    Morning, I might be misunderstanding your problem but I would have thought the easiest answer would be to compare the FEA equivalent stress to the equivalent stress allowable? I believe the check in RP-C201 is a localised yielding check for a plates structure. It's relevance will likely depend...
  13. Crannog

    Grounding of Marine Bollards

    Hi Powerkem, What are you concerned about grounding for, corrosion or electrical safety? In either case for a tied up vessel a mooring line is a pretty bad conductor. You can get issues with stray current from shore charging but I've not seen bollards influencing this. I wouldn't see any...
  14. Crannog

    DNV RP-C203 Fatigue Analysis

    Hello Reitzel, With regard the applicability of the hospot method? If I remember correctly the 1.5t (about 90mm in this case) distance for the extrapolation took the point around a 'corner' of the model into a different region so the loadings couldn't be considered to be representative of an...
  15. Crannog

    Torsion Effect on Tubular Joint design

    Do you have any images of the geometry? Cheers
  16. Crannog

    DNV RP-C203 Fatigue Analysis

    Reitzel, Thanks for the thoughts. Yes, I've got a thick plate in the joint - I think a solid model is needed to accurately capture the localised bending within the joint and welds. For similar designs with thinner plates I have shelled the models. I don't believe the DNV-hotspot method...
  17. Crannog

    DNV RP-C203 Fatigue Analysis

    Hello, I've a small offshore structure, with fatigue design to DNV RP-203 and analysed in FE (solid body). The design was sufficient to meet requirements of 2.11 such that all cyclic ranges well below Fatigue Limit [FL]. However the loads have changed and a single case is showing a design ratio...
  18. Crannog

    Welding Symbol

    Looks like: Spot weld (so no effective side (1x2) spot weld size -20 weld pitch <1> <2> are likely references to specific weld procedures, separate reference. Not sure about the SA & FB, the later might be a finish - it's in the correct place. Those in the key don't make much sense out of context.
  19. Crannog

    Eurocode 3 - compression and bending in beams

    Afternoon, I've got an issue regarding proving the suitability of a PFC section loaded in compression and bending. I've read through 6.3 in EN 1993-1-1 but it seems to give no direction for sections that aren't doubly symmetric (RHS & I?). Tata Blue Books gives sectional resistances for PFC but...

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