API TANK vs. Wind using Algor
API TANK vs. Wind using Algor
(OP)
I've been trying to model wind effects on an API 650 above ground storage tank. The model is simple enough and runs fine, however the results I'm getting are way off the mark. Has someone done this successfully before?
I've got modeled a 60' diameter x 60' tall open top tank. I've got the bottom of the shell fixed representing about 3ft of water in the tank. I have no stiffening rings anywhere. I've used thicknesses 1/4" and 3/8". The deflections I'm getting are of the order x10^-2 (0.001). I know this is incorrect, otherwise API wouldn't have us use stiffening rings, aside from what I've seen in person. The wind pressure in this case 35 psf, just above 100mph.
I think the problem with my model is trying to buckle inward a perfect cylinder. Any advice? I think that adding a dummy load to get the buckling started may work, or adding imperfections to the shell may work, but at this point how confident can I be in my results if I'm guessing and adding non-real initial loads?
I've got modeled a 60' diameter x 60' tall open top tank. I've got the bottom of the shell fixed representing about 3ft of water in the tank. I have no stiffening rings anywhere. I've used thicknesses 1/4" and 3/8". The deflections I'm getting are of the order x10^-2 (0.001). I know this is incorrect, otherwise API wouldn't have us use stiffening rings, aside from what I've seen in person. The wind pressure in this case 35 psf, just above 100mph.
I think the problem with my model is trying to buckle inward a perfect cylinder. Any advice? I think that adding a dummy load to get the buckling started may work, or adding imperfections to the shell may work, but at this point how confident can I be in my results if I'm guessing and adding non-real initial loads?





RE: API TANK vs. Wind using Algor
RE: API TANK vs. Wind using Algor
Are you using feet for all of your units?
Are you applying your pressure as a traction so that it acts more like wind with a global direction? (adding "pressure" makes the vector perpendicular to the shell element)
If you input 0.25 for the thickness, but modeled the tank in feet, you have 3" thick walls, which may not deflect quite as much as you expect.
RE: API TANK vs. Wind using Algor
I have not done a mesh sensitivity study.
I have tried non-linear with much of the same results.
I have only used fixed bottom conditions so far. I will try pinned, non-linear as soon as I can get back on it.
I have been using tractions in psi. The main wind force is about 35 psf = 0.243 psi. If my understanding is correct for an open top tank I should have a windward pressure, about the same pressure, same direction on leeward side, and pressures acting perpendicular the windward wind, pulling the middle away from the tank. I tried to mimic this roughly having 4 different surfaces.
jcoots
RE: API TANK vs. Wind using Algor
If you get a chance, upload an archive of your model without results and I'll look for any other issues.
Oh, and when you look at your results and show the load vectors, are they all pointing the correct direction?
Not sure I completely understand what you are saying about the leeward vs. windward side. What I think you are saying doesn't sound right to me, but you seem to understand your problem statement, so I'm assuming I'm just not picturing your statement correctly. If you can upload a picture of the results screen (no displacement or stress...just the FEA objects turned on) that would probably be helpful as well.
RE: API TANK vs. Wind using Algor
I do think all the load vectors are in the correct direction.
RE: API TANK vs. Wind using Algor