The OpenSees Community

Hi, Is there anyway to turn on/off the horizontal gravitational acceleration (i.e. $b1) in quadUP elements? element quadUP $eleTag $Node1 $Node2 $Node3 $Node4 $thick $matTag $bulk $fmass $PermX $PermY <$b1=0 $b2=0 $t=0> I am trying to perform a pseudo static analysis, and I want to first perform the...

Sanazzz, 1) Are your base nodes fixed? I expect them to be free to move. 2) My understanding is that the "Mulit-Support Excitation" command applies external displacements to your system. Accordingly, if your earthquake stops, there will be no external displacements added to the system. But the syste...

Thanks Frank,
We had same problem here too, and it took us lots of time to figure it out. The element/recorder removals are necessities in excavation analyses.

Regards,
Soheil

You can apply displacements to your model by using "Multi-Support Excitation" command. Just be careful, if you are applying the displacements to a fixed node, your displacements will be the average of zero and the input displacement (double check this as I am not sure).

Sanazzz, To define absorbing boundary conditions, you need to follow these steps: 1. Remove all the constraints from your base (i.e. both x and y). 2. Tie all the base nodes to one of them in both x and y directions (i.e. equalDOF Node1 Node2 1 2 - Doesn't matter which one. Take one as the master an...

Hi,

Would you please tell me if the WipeAnalysis command removes all the load patterns defined before it?

Thanks,
Soheil

Dear Frank, Thanks for the comment. The problem was that VT-Cluster server had OpenSees/2.4.5 while I am using the latest version. I checked the displacements and noticed that I am assigning fix boundaries to the base two times during gravity analyses (once before the elastic state and once before t...

Hi, I have a simple 3D model. It applies a ground motion to base of a reinforced soil profile and records the accelerations at its top surface. I run the code on my PC and results are just fine. Then I copy-paste the code to VT-Cluster server (linux machine) and run it there. The results are in orde...

Hi, I faced this problem today, and spent one full day to solve it. Then I said let's add a few lines here for future people. Hopefully, it can save some time for them. The fatal error that we are seeing, is simply because OpenSees cannot solve a 2nd order (quadratic) equation somewhere in the model...

For your recorders to save the outputs, you need to wipe out your results. For that, just add "wipe" to the end of your script.

SK

Why don't you send us your code for defining the material?

SK

Hi Omer, If my understanding is right, the number after the "material" indicates the Gaussian point at which the stresses are calculated. I am not aware of any element with 17 Gauss points. Usually in 2D problems and with quadrilateral elements, we have four Gauss point. Therefore, you recorders wil...

Hi Jhno, It really depends on the material you are using. For example if you are using ND-Material: PDMY for 2D problems you will record: Sigma_XX, Sigma_YY, Sigma_ZZ, Sigma_XY and Eta_r. Where Eta_r is the ratio between the shear (deviatoric) stress and peak shear strength at the current confinemen...

Hi, When you remove an element/node, you need to remove it and its connections (if used, e.g. interface elements) from recorder too. This should happen before performing any subsequent analyses. Note that the tags for recorders start from 0, then 1, 2, 3, ... For an example, please check: http://ope...

Hi - I am not that much familiar with rigidDiaphragm setting, but can't you remove the rotational constraints on your interested node? (i.e. using the command: remove sp $nodeTag $dof)

Regards,
Soheil