The Damping values are defined at two different locations i.e., i) Definition of Response Spectrum Function, and ii) Definition of Response Spectrum Cases. How these damping values are used?
The response-spectrum curve chosen should reflect the damping that is present in the structure being modeled. Note that the damping is inherent in the shape of the response-spectrum curve itself. As part of the Response Spectrum Case definition, you must specify the damping value that was used to generate the response-spectrum curve. During the analysis, the response-spectrum curve will automatically be adjusted from this damping value to the actual damping present in the model.
Damping in the structure has two effects on response-spectrum analysis:
- It affects the shape of the response-spectrum input curve when modal damping in the system is different than response spectrum curve. This generally occurs when dampers are present in the modal.
- It affects the amount of statistical coupling between the modes for certain methods of response-spectrum modal combination (CQC, GMC).