Damping troubles?

aemmons · Post by **aemmons** » Sun Jan 30, 2005 11:38 am

I have a model with several truss and zero-length elements. I was looking through the message board and discovered that these elements are not affected by the stiffness portion of Rayleigh damping. I think I need to define a value for $eta (damping tangent) in the truss and zero-length material definitions ie::: uniaxialMaterial Elastic 10 $E $eta

However what does this $eta (damping tangent) value phsically represent???, and how would one go about calculating this value?

I have a basic truss element, and using the zero-length for rotational springs (ie: moment-curvature relationship)

thanks

silvia · Post by **silvia** » Mon Jan 31, 2005 9:30 am

why are you using this combination of elements?

aemmons · Post by **aemmons** » Mon Jan 31, 2005 9:57 am

I am modeling the SAC 3-story structure. I am currently comparing the results to a FE model created in MATLAB. The results are very similar. The only difference in the two models that I can find is that there is currently no damping being applied to the zero-length elements or the truss elements. (if I correctly understood the previously posted message on this forum last June)

I am using rotational springs to model the nonlinear behavior of the structure, and truss elements for pin-pin connected members.

The material for the rotational springs is steel01

thanks