padeye calcs DNV 2.7-1 and 2.7-3

[dstrueng19]

Can someone please clarify/explain the difference between the contact stress/bearing pressure formula for the padeye calculations between appendix D of DNV 2.7-1 and appendix A of DNV 2.7-3. I am a bit confused with the numbers i'm getting. Thanks

 

[dhengr]

Could you post the two pertinent DNV sections, as pdf files, so we don’t have to go looking for them? I assume you’re talking about shackle pin bearing in the padeye hole?

 

[dstrueng19]

please see attached dhengr. thanks

 

[dhengr]

Dstrueng19:
First of all, those are two different codes, with a five or six year difference in their publishing dates, so in part, one hasn’t caught up with the other, more than likely. Secondly, those are empirical equations for the pin/hole bearing stress, based on research and testing, so its pretty tough to know exactly where all the values and mathematical machinations came from without going directly to the committee people who wrote the code. That is basically a Hertz bearing stress problem for a pin in a hole. It is highly dependant upon the relative dia. of the pin and the hole. The tighter the fit, the bigger the bearing area is, before any yielding even starts to take place btwn. the two parts. Thus Dpin & Dh are prominent in the equations. And, of course, the relative material properties come into play also. Maybe if you showed your actual problem we could make more sense out of it. And, while I looked at that you should click on the eye glasses at the end of the title to you thread on the main forum page. This will bring up some other similar threads, which might enlighten you. Then come back with a slightly more detailed question. Finally, we frown on double posting here at E-Tips, so red flag the post on the Struct. forum and ask the management to remove it for the double posting.

 

[Ussuri]

One thing to note is that the 2.7-1 standard you are referencing is the April 2006 revision. There was a June 2006 revision of 2.7-3 that went alongside it. In the June 2006 revision Appendix A does not exist. 2.7-1 was amended in 2008. So what dhengr talks about is possibly correct.

One standard is for Offshore Containers, the other is for Portable Offshore Units, which is basically everything else.

You need to be careful with the stresses also. 2.7-1 calculation is based on the yield stress of the material, whereas 2.7-3 is based on the allowable stress.

 

[jbeckhou]

See attached file, pad eye done to DNV 2.7-1, example only. Let me know if you have any questions.

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