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Maximize function - Multiple output issue.

MikeArmstrong
4-Participant

Maximize function - Multiple output issue.

I am working through a simplified Pipe Stress calculation and having an issue with the Maximize function. I have tried to use the Maximize function to calculate the allowable free span of the pipeline, without success.

I am looking at the stresses in two pipelines and therefore require two results from the function. I have set up a Given/Find solve block without any issues. Can anybody explain if that a limitation of the Minimize function?

Cheers

Mike

1 ACCEPTED SOLUTION

Accepted Solutions

How about the attached? Surely, sigma.s should be vectorised?

Alan

View solution in original post

16 REPLIES 16

Mike,

From the Help file: "If you are solving for n variables, the solve block must have n equations"

Alan

I appreciate that Alan, but still this issue is driving me mad.

I have two values for sigma.c and sigma.t and I'm trying to find the maximum length that x can be (x is used for calculating the free span), so the combined longitudinal stressed do not exceed 95% yield.

M11 worksheet included.

Mike

How about the attached? Surely, sigma.s should be vectorised?

Alan

View solution in original post

Cheers for taking the time Alan, but the calculated lengths should be 59.3m & 57.9m

Mike

Mike Armstrong wrote:

Cheers for taking the time Alan, but the calculated lengths should be 59.3m & 57.9m

Mike

Are you sure? These are the results you obtain without vectorising sigma.s. I've vectorised sigma.s. Without vectorising the sigma.s function just returns a single value. Is that what you intended?

Alan

Positive Alan,

Using the calculated spans in your example, the spanning stress would be above the specified yield with the other expected stresses.

Clipboard01.jpg

Mike

Sorry for the mulitple replies, the website is giving me grief.

I get the following.

Clipboard01.jpg

Mike

Ok, in that case, the attached should do it!

(Actually, my previous file was wrong also because I forgot to put subscripts on sigma.c and sigma.t!)

Alan

Cheers Alan, nice work.

You have to admit that it looks horrible though. Maybe I'll stick with the Given/Find solve block for this issue.

Cheers

Mike

I think you should compare Wp_sub.Z^-1 with Wp_sub/Z. They're not the same!

Alan

Good spot Wayne, because I had brought the Z up, the formula required the vectorize operator.

Clipboard01.jpg

Mike

I have changed this to be correct Alan.

Cheers to both you and Wayne for looking.

Mike

Hi Mike,

Your much too bright, try dimming it down to my level.

tmp.gif

MikeArmstrong
4-Participant
(To:wayne)

Hahahahahah, stop being modest Wayne.

I am actually solving for x, I'm looking for the maximum allowable span, which I have found using a Given/Find solve block, but I can't get the Maximize solve block to work.

Mike

tmp.gifMIke,

(Thanks Alan, for how to use the solve block

My original comment was in error because I did not take the sq root to get xmax, but the point is that is easy to solve for directly. Why use a solve block?

Anyway, I get these lengths (Maybe I goofed)?

MikeArmstrong
4-Participant
(To:wayne)

Wayne Reid wrote:

tmp.gifMIke,

(Thanks Alan, for how to use the solve block

My original comment was in error because I did not take the sq root to get xmax, but the point is that is easy to solve for directly. Why use a solve block?

Anyway, I get these lengths (Maybe I goofed)?

I goofed, not you Wayne.

When I submit the calculation I will transpose the formula as you have done. I was simply playing around with the Maximize function.

Cheers

Mike

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