total strain increment

kyonten · Post by **kyonten** » Tue May 26, 2009 8:12 am

It seems the strain that is passed to the material user subroutine/interface is the Total Strains. Is there a way to access the Total Strain Increments? One approach could be to save the previous total strain as state variables, and then subtract it from the current total strain to get the increment. If the total strain increment can be directly passed to the material user interface, I would prefer that option.

Post by **fmk** » Thu May 28, 2009 1:50 pm

OpenSees does not return strain increments .. however you can calculate it in the script using two variables:

set strain1 ...
analyze 1
set strain2 ..
set strainIncrement [$strain2 - $strain1]

kyonten · Post by **kyonten** » Fri May 29, 2009 7:49 am

Thanks, Frank! I needed strain increments for the user material implementation. I don't think I can pass the strain increments to the material model via the script you mentioned.

rjaeger · Post by **rjaeger** » Sat May 30, 2009 8:14 am

Hi,

Depending on which type of material you have, you can do something like this:

strain_incr = input_strain - commit_strain which would be the strain increment from the last committed step.

Robbie

kyonten · Post by **kyonten** » Sat May 30, 2009 8:55 am

Thanks. Actually, that's what I'm doing since I have access to the "committed" strain.