I have been working on a subsea project and the client wants the piping to be designed to both ASME B31.8 and DNV-RP-F112. I am currently using AutoPIPE to run all the piping analysis, but its results are only per B31.8 (hoop, longitudinal & combined).However, DNV-RP-F112 gives its allowable in terms of (membrane & membrane + bending....stress linearization)My question; is there a way of obtaining membrane & membrane + bending stress components from B31.8 stress components?Any help or nudge in the right direction is greatly appreciated. DNV-RP-F112 - "Design of duplex stainless steel subsea equipment exposed to cathodic protection"
AutoPIPE calculates membrane (or LONG) and membrane + bending (COMB) for each code combination except for hoop. For example
Load In-Pl. Out-Pl. Shear Axial Bending Code Code
combination Moment Moment Stress Stress Stress type Stress Allow.
--------------- ------- ------ ------ ------ ------ ---- ------ ------
GRT1+W1{1} 7951 1994 2192 3288 11327 COMB 16860 31500
1484 5852 LONG 7336 28000
The stresses are calculated using Tresca stress as per B31.8 and the allowable are set to 0.8 SY (Long) and 0.9 SY (Comb). Hoop is set to 0.5 SY. These allowable stress factors can be adjusted in Tools/Model/Options/Result (F1, F2, F3 factors). DNV-RP-F112 factors are 0.8, 0.8, 0.8 but all based on Von Mises stress instead of Tresca. To cover both codes I would just change F3 to 0.8.
You may edit the code combinations and change the category from Func and Func+Env to Von Mises. To do so you would need to uncheck the AutoUpdate for the combination and then double click to change the category to Von Mises. You may also create a duplicate of the combination and change the category in one of them.
Please note that Tresca stress is larger than Von Mises stress.
Regards,
Karim
Thanks alot. I will look into this and follow up with any questions.