energy dissipated through Rayleigh damping

[GiuseppeDelGobbo]

Hello,

Is there a straightforward way to calculate the energy dissipated through Rayleigh damping in OpenSees? The methods I can think of would require the stiffness matrix to be output at every timestep of the analysis if damping proportional to tangent stiffness is used. This ends up being too resource intensive. Thanks,

[selimgunay]

That seems to be the only way at the moment. I checked the code and could not find a recorder that outputs the energy.

Printing the stiffness matrix, adding the mass component on that and computing the energy by integration of damping matrix multiplied by the displacement increment may not be that difficult with a Matlab postprocessing code. You only need to be careful in match the dofs to those of the stiffness matrix. If you are using RCM numbering, they would be re-numbered.

[sb1966]

Hi,
This might not be an exact response to the question.

However, it is possible to determine the Damping ratio by measuring the area within a particular hysteretic loop. For this, (a) one may use an element recorder to record the (shear) stress and (shear) strain and (b) then calculate the area within the loop by numerical integration. (c) Then the damping ratio can be calculated for that loop by using standard procedure (e.g. Kramer, Geotechnical Earthquake Engineering).

By recording the dT used in analysis, the duration of the loop can be checked and thus, any particular loop can be selected which is relevant in the analysis.

The whole process can be automated using MATLAB or SCILAB script or any other language of choice for post processing.