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Hello Frank, By aligning the acceleration calculation to newmark's method (also my integration method),the code worked pretty well. I just have two more questions regarding Opensees: (1) For the above to work, I need to set GetDampedTangent method to return a value proportional to the inverse of dt,...

Dear fmk, Thanks for your reply. I think this method works well, but there is something I do not quite understand. In implementing a mass damper material, here is my main code, where C is the mass of the mass damper, and I left getTangent, getInitialTangent, and getDampedTangeng methods to return 0;...

I guess for now my primary concern is accessing ops_Dt with a dll

For some reason I believe ops_Dt is giving me 0 all the time. Is there a way around this?

Hello fmk, Here is what I have done so far, I tried to create a viscous material using the strains and the global delta T, but it seems ops_Dt is 0 as my displacements and velocity are either #IND or #QNAN. Also, if I replace ops_Dt with a finite number (e.g. 0.05), it gives reasonable results, but ...

Hello fmk, thanks for the reply. This is from the code I presume. What I am trying to to do is to basically create a damping material that provide damping force proportional to the acceleration. In the source code for uniaxial viscous material, where the damping force is proportional to the velocity...

I found a simple solution. You would just record the element force for that material (in my case it is an uni-axial viscous material).

Hello Everyone,

Is there a way to measure viscous damping forces? I tried using node recorder - rayleighForces but everything is 0, so i suspect it does not apply to viscous damping.

Hello Everyone,

I was wondering if there is a build-in function that can get trail accelerations?

For instance, in elastic material, we use get strain
in viscous material, we use get strain rate
I'm trying to find if there is anything that can get the "rate of strain rate"

Appreciate your help!