The OpenSees Community

Is the 3rd DOF constrained in at least one node (e.g. surface nodes should have 0 pore pressure)?

I think OpenSees is perfectly capable of doing both static and dynamic analyses and should be use for both.

Analytically, there should be the capability of using Mohr Coulomb, Modified Cam Clay ,and the hardening soil model (very common in plaxis). The first two exist but their implementation inside the NewTemplate3Dep is too complicated, and, to my opinion, wastes time in too many function calls. The hardening soil model is very useful and should be implemented.

Have a procedure to initialize the state of the model. For example, in the mutliyieldpressure dependent I have to use the elastic mode of the model run one analysis and then the elastoplastic. This is not sufficient since the initial stresses are not represented exactly. In the DM soil model I have to run an independent elastic analysis, store the data in an array and use this as initial conditions withouth running an elastic step. As you can see there is not a unified way to apply the initial geostatic conditions. VERY IMPORTANT PROBLEM.

The DM soil model as implemented does NOT work for low stresses (even after a very important bug i fixed and send you last year). I have a version that uses various algorithms to improve the integration of the model that works for my models, which I could share at some point, but this is definitely an issure!

In soils it is common that some region is saturated (u-p elements 3DOF) and some region is not satureated (normal quad 2dof/node elements). So in a model that i have both elements i have to create double the nodes in the interface and then connect them with equalDOF objects! Very time consuming. I would add a command in OS that would be something like:
map quad quadup 1 2 1 2
which would say that the dof 1 and 2 at every node on the quad element correspond to dof 1 and 2 on the quad up element. This is way the elements will share nodes and OS will know how to create the stiffness matrix.

Partially saturated soils! It would be great to see some sort of model being able to predict the mechanical behavior of these soils.

Fluid solver, to be able to do e.g. dynamic embankement analysis next to the sea level! Very important. If this is too big of a task we can get some people to try and work on an ABAQUS element to connect OS with ABAQUS fluid solver with OpenFresco (I had some correspondence with Andreas some time ago).

Large displacement u-p elements for plane strain. Speaks for itself, very much needed for 2d liquefaction simulation.

Last, a way to automate free field absorbing boundaries similar to Flac. Today this can only be done either with extensive manual input (which I am doing), or with rough simplifications.

Thank you very much,

Please do not hesitate to contact me for more details, I've working with OS for many years and I would like to see the geotechnical modules improve and become useful in so many more cases!

Is there a way to find cumulatively all the changes between distributions? Or give dates and compare all the files that changed between them?

Thanks!

Not a problem, just use the up elements (2D or 3D depending on your problem).

which version of OS are you using?

if you go to the ucsd opensees site they have examples illustrating the use of the updatematerials command
(e.g. cyclic.ucsd.edu/opensees/soil2/soil2.txt)

if they do not work then there might be a problem with your version.

this command works fine with my version I have (latest version through cvs).

how do you initialize your stress conditions? do you match elastic poissons ratio with K0 and then check to see if the stresses of the elastic step are correct?

If you are having problems with stiffness constrast you can choose any stiffness you want to get your elastic initial stresses right and then change the shear and bulk moduli to the right values by using the updateMaterials command. This might be the best option to my opinion.

I am not sure I can see any way to apply the load incrementally the way you define it. Maybe you can write a subroutine similar to the updatematerials command that can update the gravity in the quadup elements.

Is there any use that when the test increment (energy, displ, force) becomes INF or NAN the analysis object does not return a failed analysis?

At least in my analyses (geotechnical eaqrthquake engineering) it is confusing and time-consuming.

Hi,

I remember some years ago it wasn't right to use transformation handler if you have objects that tie to other objects, that tie to other objets.
(e.g.
equalDOF 1 2 1 2
equalDOF 2 3 1 2
)

Is it still a problem? Do we still need to use penalty handlers for this type of problem?

Antonios

Hi all,

I am using MultipleSupport to apply some boundary pore pressure boundary conditions.

The problem is that, in my model, if the imposed motion objects are more than 85 then opensees will stop. (i will get a windows error message - no output concerning problems in my model)

I've tried putting imposed motion in multiple multiplesupport objects, applying them in different nodes, or changing their labels to make sure there is no problems with other labels in my model but it still does not work.

Any insights??

Antonios

For the UC San Diego Soil Elements
> FourNodeQuadUP elements

I haven't tried it on the other three UCSD soil Elements but since for all the four elements the velocity of the third DOF is the pore pressure then it should work for all four.

To set pore pressure to be $p at node $NodeID then one should write:

set Timeseries "Constant -factor $p"
pattern MultipleSupport 1 {
groundMotion $GMID Plain -vel $Timeseries
imposedMotion $NodeID 3 $GMID
}


-------------------------
for "Indicate how can one apply pore pressure conditions conditions in the UCSD quad-up elements:
set Timeseries24 "Constant -factor 134.56"

pattern MultipleSupport 2 {
groundMotion 24 Plain -vel $Timeseries24
imposedMotion 24 3 24
}
"

can you please be specific as to which elements (where should i put it into the manuaL)

thank you!

> in the recorder specify the option to choose a recording timestep:
-dT $dt

> Specify that the zerolength elements can only connect 2DOF nodes.

> indicate how to remove recorders
(e.g.
set a [recorder $arguments]
remove a
)

> Also discuss removing fixities.

>Indicate that the model basicbuilder command can be used many times in our model to define different DOF regions.

>Indicate how can one apply pore pressure conditions conditions in the UCSD quad-up elements:
set Timeseries24 "Constant -factor 134.56"

pattern MultipleSupport 2 {
groundMotion 24 Plain -vel $Timeseries24
imposedMotion 24 3 24
}

>I think there is no documentation on the multiaxialcyclic plasticity model (there is the relevant info in the source files)

>setTime command

>loadconst command

Check this out:

web.mit.edu/avytin/www/site_files/Microsoft%20Word%20-%20Manual%20Centrifuge.pdf

What is the reaction recorder recording in a node that is tied with another one with equalDOF objects? Is it correct to use it to get the internal forces between the two nodes?

try something like that:

# Creating a recorder:
set r_1 [recorder Node -file output_disp_31.txt -nodeRange 1 4204 -time -dT 1. -dof 1 2 disp]

# destroying the recorder:
remove recorder $r_1

yes