Reference for 3D-Template Elasto-Plastic Material

[timosidis]

I am trying to use 3D Template Elasto-Plastic Material to model Concrete in a 3-Dimension problem. I don’t know what “tensorial internal variables”, “scalar internal variables” and “initial values for scalar internal variables” in Elasto-Plastic State are. Could anybody please give me a reference (for 3D-template material generally or for elasto-plastic state specifically)?

[Boris Jeremic]

HEllo Timosidis,

Internal variables, are together with the current state of stress
controling the behavior of material. INternal variables are in general tensors of even order. In other words, they can be scalars (for isotropic hardening), second order tensors (for kinematic hardening), fourth order tensors (for distortional hardening) and so on. For example, simple scalar internal variables can be frictions angle (for Drucker Prager yiels surface), or uniaxial strenght for von Mises surface or isotropic confinment (P_0 for Cam Clay models). For kinematic hardening you have second order tensors for internal variables, say a back stress a_ij ... The distortiional hardening uses fourth order tensors to describe hardening process, not much work in that area unfortunately, eventhough there is very strong evidence that this type of hardening is actually omnipresent. This type of hardening (distortional) is also the most general one, and it encompases both kinematic and scalar types... Graphically scalar hardening changes the size of yiels (or potential) surface, kinematic translate or rotates the surface and distortional will change the shape of the yield surface.

Take a look at some of my papers (see my web page) and also look at the lecture notes available throgh the same URL:


http://sokocalo.engr.ucdavis.edu/~jeremic/


There are also a number of example scripts in ExampleScripts subdirectory in OpenSees CVS repository.

Best regards, BOris

[Paolo Franchin]

I have just started trying to use the Templated3Dep material model. I have refreshed my computational mechanics, I have downloaded the examples from Prof.Jeremic website (in particular the single pile embedded in sand example, very well written) and I started by both writing simple scripts and trying to run the downloaded example. Apparently the syntax described in the manual and used in the input files does not work. I was using OS 1.6.0 and switched now to 1.6.1. I keep getting this message (trying to use a Drucker-Parger yield surface):

nDMaterial Templated3Dep - invalid elastic material tag -DP
WARNING count not create nDMaterial: Template3Depexpected integer but got "-YS"

Is it possible that, since the example date back to 2002, the syntax refers to an older OS version and has been changed?

Thank you in advance

[Boris Jeremic]

Hello Paolo,

Yes, the command has changed a tiny bit (but enough that the old interface is broken). What we have done is to attach the elastic model to the EP state. All the basic examples are updated but the big one (the single pile example from that paper) is not. Will do it in next couple of days.

Revised commands are available (among other commands) at:

http://sokocalo.engr.ucdavis.edu/~jerem ... mmands.pdf

We' ve also send the update to the maintainer of main OpenSees manual (Silvia) but it seems that she has not incorporated them in there yet...

We have quite a bit more examples, in all areas, and in particular something that you might be intersted in, new single pile and pile grop examples where we model the pile as inealstic beam-column element (allowing for realistic yielding)... There are some links from my research web page to those examples, but I am working on organizing all the examples in a comprehensive set that will be used as illustrations for lecture notes:
http://sokocalo.engr.ucdavis.edu/~jerem ... eNotes.pdf

(will be part of now empty chapter 8: Applications).

Let me know how it goes with this endeavor!

Best regards, Boris

[Boris Jeremic]

I forgot to mention that any new features we add to OpenSees (or others) will end up in executables we provide for MS Windows at:

http://sokocalo.engr.ucdavis.edu/~jerem ... ECUTABLES/

We had to do this as there were too many emails asking why is certain feature we implemented not available in windows version (there are quite a bit of revisions and additions between major releases, like say between 1.5 and 1.6). Think of this as executables for any minor revisions in OpenSees (and it will be updated again early next week when we update the u-p-U elements.).

Frank: how often do you do MS Win compiles and posts of exec on the web?

Best regards,
Boris

[fmk]

i try and upgrade the windows .exe after some important bug fix or after enough new features have been added .. typically about once a month or so .