a lot of load cases

[beastgod]

Hello everybody.

I have a column vessel. It has the loads: D, P, W.
Let L and T equal 0.

So, I would like to evaluate the column according ASME BPVC VIII div2.
I use elastic-plastic analysis, so I use load combinations from table 5.5.
1) 2,4(P+D)
2) 2,1(P+D)+1,7W

As you know, W has different directions, so I choose 4 - North , South (s), West (w) and East (e).
My combinations now become:
1) 2,4(P+D)
2) 2,1(P+D)+1,7W
3) 2,1(P+D)+1,7W(s)
4) 2,1(P+D)+1,7W(w)
5) 2,1(P+D)+1,7W(e)

It needs more efforts, but I can do it. However...
when I try to evaluate protection from ratcheting it appears a lot of load cases. Examples in attachment.

http://files.engineering.com/getfil...9eba-88bd2f363450&file=Load_combinations.xlsx

Of course some of them I can delete (some highlighted in red), but there are still enough combinations.(about 50).
Can anybody give me advice what I should do? What do you usually do in such cases - use your experience and delete most of combinations or directly solve all cases?

Sincerely, Alexis

 

[JStephen]

On completely different work:
If it is obvious that certain load cases will not govern, then say so and don't evaluate them.
If it is possible to combine different load cases with a single envelope, it may simplify things.
If necessary, make 50 columns on your spreadsheet and evaluate 50 load cases, etc.
Note that some cases may not govern your design, but might govern foundation design.

 

[TGS4]

In my opinion, you need to be applying your engineering judgement much more in these situations. Whether your wind is from one particular cardinal direction or even if you have a quartering wind really ought not to matter for your calculations. If it does, then determine the worst direction and run with that.

In the consideration of pressure being zero or design, note that the terminology in the Code is that such a situation must be "considered", which is not to say that it has to be "evaluated". Does that make sense?

Now, as far as the ratcheting check goes, the directions in the Code are very clear - it is for the evaluation of operating load cycles. If you will normally operate from zero pressure with full wind in any one of the four cardinal directions, to full pressure with any of the other wind directions, then I guess you will have to evaluate ALL of the conditions that you listed. However, the intent of the ratcheting check is that the actual operating situations are examined. Generally speaking, for example, that is not going to include wind.

 

[beastgod]

Thaks for your answers!
So I think in my case the only way is using my engineering knowledge.
Thus I don`t want to consider the wind load while I evaluate ratcheting. And I try to choose the worst direction of the wind to delete the most of cases while I evaluate protection from plastic collapse.

"make 50 columns on your spreadsheet and evaluate 50 load cases, etc."
-One model takes a lot of time to computate, 50 will take much more...My computer can`t do this