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ptc-66024011-Visitor
1-Visitor
March 25, 2015
Question

Sort Through Multiple Matrices to Identify Controlling Value v14

  • March 25, 2015
  • 2 replies
  • 1460 views

I have created a sheet and come to the end where I now need some help with a routine I believe. I have a thickness variable titled t.g and the corresponding Performance Ratios shown next to those thicknesses. The columns represent the grades of steel I am using. Now i need a routine to look through all three matrices and find the first instance of when all three have a value of 1.0 or greater. When that occurs I would like it to output what thickness and what grade of steel that corresponds to. Attached is my sheet. Any help would be greatly appreciated.

2 replies

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RichardJ19-Tanzanite
19-Tanzanite
March 25, 2015

Mu/Mr is never greater than 1. The first instance of Pu/Pr or CSR being greater than 1 is simply the first element in each matrix.

I guess I'm missing something here

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ptc-66024011-VisitorAuthor
1-Visitor
March 25, 2015

Richard -

Sorry ... I now realize how confusing my original post was. Let me see if I can do better this time.

The 3 different ratios can be called performance ratios. The idea is that the closest you can get to 1 without exceeding 1 is the most economical design. The thing is that all 3 ratios must satisfy this requirement for it to work. For the example I posted if I look at thickness of t.g = 0.375 in and using Grade 55 ksi steel (row 3, column 2 in the performance ratios) I can see the requirement is satisfied for Mu/Mr = 0.002 and CSR = 0.944 however for Pu/Pr = 1.077. So this would not work. My goal is to write a routine that can find the first one that satisfies this requirement for all three as this would be the most economical. And then the ultimate goal would be for the routine to return the thickness and grade to me. For my example that would be t.g= 0.438in using 50 ksi steel (row 4, column 1. All of the performance ratios are less than 1.0).

PS ... The example that I posted is poor because I forgot to input a value for Mu.that has any significance. In most instances this will be approx. 500 kip-ft or more.

Thanks for taking the time to respond to me. I really appreciate it.

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AndyWesterman12-Amethyst
12-Amethyst
March 26, 2015

Attached shows one method.

1.create local copies of the arrays.

2.eliminate the values >1 (change to -100)

3.form a composite of the 3 arrays (I chose min(...) - selection of this function dictated the -100 in step 2)

4.find the maximum value that remains.

step 3 is the one that you will need to be most careful of especially if you want to adjust the weighting of the various parameters

Regards

Andy

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