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I did the following linear elastic analysis:

initialize

system BandGeneral

constraints Transformation

numberer RCM

test NormUnbalance 1e-12 20 1

algorithm Linear

integrator LoadControl 1

analysis Static

analyze 1

I guess I can assume that we cannot see the stress results for the quad element? Is this correct?

I am trying to "load" a quad element with prescribed displacements. The command I have tried is: pattern Plain 1 Linear{ sp 2 1 0.1 sp 3 1 0.1 } This of course is intended to displace nodes 2 and 3 by 0.1 inches in the x-direction. All I get are blank output files when I try this. Where is...

I am trying to record the stress in a quad element, or output to a file in some manner. The recorder commands I have used are: recorder Element -file Q4stress.out -ele 1 stress which gives a blank output file recorder Element -file Q4stress.out -ele 1 Stress which also gives a blank output file I al...

I'm not finding much on "arpack". What is the basic method used for calculating eigen values? Power method? Inverse iteration? Subspace method? Other?

I've gotten the series of four commands to give me an output file.
I seem to get the same eigen values for the standard or the generalized eigen command. And I do have mass defined at each node. What's
up with this?

Actually, ya, I think there should be 4 components with 4 free dofs, not 2 like I had indicated. Some times I get 4, other times 8. The biggest dilemma is which vector goes with which eigen value? Also, I am presuming that the list of numbers corresponds to the list of dofs in the "-dof 1"...

I am now getting numbers, but seemingly too many numbers. The numbers of course vary depending on what I put in the recorder command. I am using a quad element with 4 of 8 dofs fixed. My eigen command is: eigen frequency 3 For the recorder I have tried a number of different combinations: recorder No...

I really am not understanding how to record the eigen values or eigen vectors when using a quad element (or any continuum element).

Can you supply me with instructions?

I can't get stresses to record. This si the command I am using, but my output file is empty.


recorder Element -file stress.out -ele 1 stressStrain

I tried that, now I'm not getting any output file.
How can I actually record the eigen values?

I am presuming that the last part of the eigen recorder "eigen 2" should match the eigen command exactly? I notice that when I use the command: eigen 2 and the recorder: recorder Node -file Q4eigen.out -node 2 3 -dof 1 2 "eigen 1" I get different values recorded. Am I correct in ...

I am getting negative eigen values using a quad element. The script is quite basic, it sure looks like the element has nodes defined counterclockwise as required. The element works well when applying pure shear or pure axial loads. But the eigen values are: -9.24198 -0.89034 -9.24198 0.89034 Here's ...

I have the eigen command working now. But it won't record the eigenvalues. I've been looking at the manual (p. 228, 229) and that doesn't record my eigenvalues. It does record the reactions if I put the nodes and dofs into the command. For example: recorder Node -file Q4.out -dof 1 eigen This gives ...

I presume the stresses and strains are calculated at the integration points.
Are they also recorded at the integration points? Or at the nodes?