BUOYANCY Weight.

Dear all,

I am doing a subsea piping stress analysis. i have done the anlysis based on Chapter IX of ASME B 31.4. All the environmental inputs(Wave, Current and water depth) have been applied to the model. Now i am confusing with the BUOYANCY weight. By referring previous descussion regarding BUOYANCY held in the forum i have understood that when we are applying wave load then caesar II will calculate the BUOYANCY weight , ie W=Weight + BUOYANCY weight. but i was not able to find out any thing about this in CAESAR II user guide and Technical Reference manual.I need to explain this in my report because my client is asking for the BUOYANCY weight.

Does anybody knows about how to consider the buoyancy weight in CAESAR II. Also I want to know do there have any option for geting these BUOYANCY values in the Input Report?

Thanking you
Rej..

If you include a WAVx primative in any load case, then the weight primative "W" is actually "W+Buoyancy".

You can prove this by defining a submerged cantilever, with some small generic wave loading. Then make two runs:

1) In Run1, just define a single load case with "W", run the analysis and note the vertical reaction load.

2) In Run2, define a second load case with "Wav1", run the analysis and note the vertical reaction load for 'case 1 - W'.

Richard,
Ok i understood, but what about wave load. Do it possible to get seperate output for wave loading in CAESAR II?

thanking You

Sure, just run a case with only WAVx as the load primative.

Richard

thanks for your reply, i need one more advise from you which i have mentioned below:
Can you please explain the load case for this suggested run, only WAV load is consider or what?
i.e, "W+WAV1" is the load.

Please clarify this one also.

Thanking You
rej

For this set of loads:


1) W (OPE)

"W" will be the usual (air) weight of the system.

For this set of loads:

1) W (OPE) ---------- W will be the buoyant weight of the system (W+BUOY)
2) WAV1 (OPE) ------- WAV1 will be the effects of only the 1st wave vector
3) W + WAV1 (OPE) --- will be the combined effects of (W+BUOY+WAV1)

Thank you Richard.....Now i can fill the clent requirements.
These kind of supports from your's side are always appreciable bcause i am the only man suggesting CAESAR in my company for doing subsea piping and riser analysis.

Richard,

This means that ones i will activate wave for my system, it will take buoyancy in whole system irrespective of load cases.

Yes, any "W" will mean "W+Buoy" if (and only if) "WAVx" is included anywhere in the load sets.