Modal analysis for unanchored tank

Question

Modal analysis for unanchored tank

alishst (Structural)

(OP)

15 May 19 22:14

Hi

I'm trying to model an unanchored storage tank using FE software Abaqus. I wanna run a modal analysis and find out the frequencies for main impulsive and convective modes. However, I need some analytical equations for these two in order to verify my results. Is there any design code or scientific paper which could help me check my analysis?

JStephen (Mechanical) · Answer 1 · 2019-05-16 05:05:45

Try this for starters:
https://pdfs.semanticscholar.org/9351/cd259d0ae432...
He references a paper by Veletsos which is the main reference for the impulsive period.
If you have a current API-650, it includes formulas for both impulsive and convective periods as well.

alishst (Structural) · Answer 2 · 2019-05-16 19:21:33

I had previously checked API 650 for 2007 but it only has impulsive/convective periods for anchored tanks and doesn't give any separate equation for unanchored (or self-anchored in their own words) tanks. Which edition are you referring to?

JStephen (Mechanical) · Answer 3 · 2019-05-17 14:56:50

For normal design purposes, the periods are assumed the same whether anchored or not.
I don't recall seeing anything on change in period with significant uplift. I would think somebody has looked into that, but not a standard design consideration.

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Modal analysis for unanchored tank