Dynamic analysis doesn't run
Dynamic analysis doesn't run
Hi STKO team,
I'm new to STKO and I'm trying to model a deposit of 7 layers of soil with different properties and weight.
I built the geometry of the 2D model importing it from an AutoCAD drawing. Then I drew construction lines to get the quadrilateral mesh and I did the merge operation on the entire geometry.
I ran successfully the gravity analysis and now I'm trying to run the dynamic one adding ASDabsorbing Boundaries(2Dauto). I used as imput motion a Ricker Wavelet.
STKO doesn't run the analysis and shows the error window below: I don't understand how to solve it. I attached the files of the whole model so you can understand what I've done. Can you help me realize what's wrong?
Therefore I'm in doubt about the necessity of extending the sides of the geometry in order to avoid the reflection of incoming waves. Are the ASDAbsorbingBoundaries2Dauto an alternative to the extension or it is still convenient to do it?
Wait for your reply.
Thank you for your time and help.
I'm new to STKO and I'm trying to model a deposit of 7 layers of soil with different properties and weight.
I built the geometry of the 2D model importing it from an AutoCAD drawing. Then I drew construction lines to get the quadrilateral mesh and I did the merge operation on the entire geometry.
I ran successfully the gravity analysis and now I'm trying to run the dynamic one adding ASDabsorbing Boundaries(2Dauto). I used as imput motion a Ricker Wavelet.
STKO doesn't run the analysis and shows the error window below: I don't understand how to solve it. I attached the files of the whole model so you can understand what I've done. Can you help me realize what's wrong?
Therefore I'm in doubt about the necessity of extending the sides of the geometry in order to avoid the reflection of incoming waves. Are the ASDAbsorbingBoundaries2Dauto an alternative to the extension or it is still convenient to do it?
Wait for your reply.
Thank you for your time and help.
 Attachments

 sezione trasversale.zip
 (265.97 KiB) Downloaded 32 times
Re: Dynamic analysis doesn't run
The drawing you did in AutoCAD is not precise.
For example, the left vertical side is not strictly vertical, you can see it by zooming, or by doing a query of the bottom and top vertex position: The Automatic absorbing boundary assumes the sides to be perfectly horizontal or vertical.
For example, the left vertical side is not strictly vertical, you can see it by zooming, or by doing a query of the bottom and top vertex position: The Automatic absorbing boundary assumes the sides to be perfectly horizontal or vertical.
Re: Dynamic analysis doesn't run
Thank you for your prompt reply and the assistance in solving the analysis problem. I fix the problem and it is working fine.
What about the matter of expansion of geometry mentioned above?
What about the matter of expansion of geometry mentioned above?
Re: Dynamic analysis doesn't run
The absorbing boundaries should be able to absorb outgoing waves. Of course, how far you should place your boundaries depends on your problem. Looking at your model it seems reasonable what you did.
Re: Dynamic analysis doesn't run
Hi again,
I'm Martina and I'm working together with Fabiola in this project. We are modeling a 2D site response of a multilayered deposit, as mentioned above. In order to model the degradation of soil’s secant shear modulus with the change of shear strain we used the PIMY (PressureIndependMultiYield) material.
We have experimental G/Gmax curve for every soil type so we added that in the $r, $Gs section.
Should shear deformation data be entered in %?
Secondly, we have some issues with damping modeling.
It has been said in other posts that this material inherently accounts for damping so you should not add additional damping to the model. We have some trouble understanding how the material works and how the damping is taken into account.
Many nonlinear soil models to describe the hysteretic behavior for unloading and reloading follow Masing’s rule, is this the case?
If masing rule is adopted, zero damping is implemented at small strain level, where the modulus reduction
curve is linear and it contradicts laboratory test observations. So should we model an additional damping? in which case, should we use a Rayleigh damping for each soil type?
Thank you in advance for your help,
Martina
I'm Martina and I'm working together with Fabiola in this project. We are modeling a 2D site response of a multilayered deposit, as mentioned above. In order to model the degradation of soil’s secant shear modulus with the change of shear strain we used the PIMY (PressureIndependMultiYield) material.
We have experimental G/Gmax curve for every soil type so we added that in the $r, $Gs section.
Should shear deformation data be entered in %?
Secondly, we have some issues with damping modeling.
It has been said in other posts that this material inherently accounts for damping so you should not add additional damping to the model. We have some trouble understanding how the material works and how the damping is taken into account.
Many nonlinear soil models to describe the hysteretic behavior for unloading and reloading follow Masing’s rule, is this the case?
If masing rule is adopted, zero damping is implemented at small strain level, where the modulus reduction
curve is linear and it contradicts laboratory test observations. So should we model an additional damping? in which case, should we use a Rayleigh damping for each soil type?
Thank you in advance for your help,
Martina
Re: Dynamic analysis doesn't run
This is the description of the userdefined surface type:We have experimental G/Gmax curve for every soil type so we added that in the $r, $Gs section.
Should shear deformation data be entered in %?
you can define yield surfaces directly based on desired shear modulus reduction curve. To do so, provide noYieldSurf pairs of shear strain (γ) and modulus ratio (Gs) values.
The number of columns must be 2 and will be considered up to 39 rows
That is, you can enter a Nx2 matrix, where N is at most = 39. The first column is the strain, the second is the modulus ratio
No in that sense... In the sense that a nonlinear material model already introduces nonlinearity. While rayleigh damping is used to introduce all the non linear behavior that are not physically introduced in the model.It has been said in other posts that this material inherently accounts for damping so you should not add additional damping to the model. We have some trouble understanding how the material works and how the damping is taken into account.
But no material model is so accurate to include every nonlinear effect.
Re: Dynamic analysis doesn't run
Hello Team,
I'm here asking again for your help. I have some issues with the convergence of the analysis in my model.
I'm using a PIMY material so I set a static analysis (Analysis 1) at first using elastic stage material. Then I updated the plastic stage and set a transient analysis (Analysis 2). I also set an additional analysis after Analysis 2 (Dummy analysis) in order to relax any spurious oscillation. Once this is done, I activated the absorbing boundaries and ran the dynamic analysis, but it shows a very high acceleration. I tried to change the analysis parameters but I couldn't be able to solve the problem.
I attached the file below. Could you please have a look at it?
Thanks in advance for your help and your support again.
Fabiola
I'm here asking again for your help. I have some issues with the convergence of the analysis in my model.
I'm using a PIMY material so I set a static analysis (Analysis 1) at first using elastic stage material. Then I updated the plastic stage and set a transient analysis (Analysis 2). I also set an additional analysis after Analysis 2 (Dummy analysis) in order to relax any spurious oscillation. Once this is done, I activated the absorbing boundaries and ran the dynamic analysis, but it shows a very high acceleration. I tried to change the analysis parameters but I couldn't be able to solve the problem.
I attached the file below. Could you please have a look at it?
Thanks in advance for your help and your support again.
Fabiola
 Attachments

 SL_PIMY V2.zip
 (360.3 KiB) Downloaded 21 times
Re: Dynamic analysis doesn't run
The postelastic analyses have a very large error tolerance:
a tolerance of 0.01 in NormDispIncr means that you are accepting an error of 1 centimeter (since you are modeling in meters).
Also, the plastic gravity analysis is made transient with a duration of 1 second. It may induce too large accelerations since the change from elastic to plastic happens suddenly.
I tried to change the parameters but it will take a lot to converge. It looks like all the upper layers in your model entered a deep nonlinear state already from gravity. Here is the last component of the stress tensor which gives an idea of the level of nonlinearity:
This is the strain localization band, which also shows the level of nonlinearity you are having:
Of course, this sudden change from elastic to plastic generates some spurious accelerations. However, as you increase the time of the gravity analysis (I used 100 seconds), the inertia effects will be lower
Here is my file. play with it and let us know:
a tolerance of 0.01 in NormDispIncr means that you are accepting an error of 1 centimeter (since you are modeling in meters).
Also, the plastic gravity analysis is made transient with a duration of 1 second. It may induce too large accelerations since the change from elastic to plastic happens suddenly.
I tried to change the parameters but it will take a lot to converge. It looks like all the upper layers in your model entered a deep nonlinear state already from gravity. Here is the last component of the stress tensor which gives an idea of the level of nonlinearity:
This is the strain localization band, which also shows the level of nonlinearity you are having:
Of course, this sudden change from elastic to plastic generates some spurious accelerations. However, as you increase the time of the gravity analysis (I used 100 seconds), the inertia effects will be lower
Here is my file. play with it and let us know:
Re: Dynamic analysis doesn't run
Thanks for your help.
As recommended, i have reduced the tolerance to 1*107 and I decided to change the algorithm type (BFGS) because I saw that it takes less time.
For the deep nonlinearity I tried to change the alpha (0.6) and beta (0.3025) values in the integration Newmark method. The model works with some tolerance errors on the displacement but i think i can accept it. I attached the file below.
I also have a question, is it possible to get the response and fourier spectrum in the outputs?
Thanks again,
Fabiola
As recommended, i have reduced the tolerance to 1*107 and I decided to change the algorithm type (BFGS) because I saw that it takes less time.
For the deep nonlinearity I tried to change the alpha (0.6) and beta (0.3025) values in the integration Newmark method. The model works with some tolerance errors on the displacement but i think i can accept it. I attached the file below.
I also have a question, is it possible to get the response and fourier spectrum in the outputs?
Thanks again,
Fabiola
 Attachments

 SL_PIMY V1.rar
 (270.66 KiB) Downloaded 23 times
Re: Dynamic analysis doesn't run
It's fine because 1.0E7 in meters is pretty small as an absolute error.The model works with some tolerance errors on the displacement but i think i can accept it.
Not as a builtin command, but you can use the PythonAPI to post process any response provided by OpenSees.I also have a question, is it possible to get the response and fourier spectrum in the outputs?
Have a look at the webinar "Intro to PythonAPI"