Thanks Avnish
The standard recommends testing the system to determine damping. My confusion is that there will be different damping values for each system mode.Â
Maybe a more concrete example would be helful. If there are 3 SDOF mass-spring dampers connected in series, and the leftmost is connected to ground. Say the first body has damping ratio = 10%, the second = 5% and the third 1%.
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If I am trying to find the repsonse of the third body, which damping value would be used for input. Using 1% does not seem correct since this body is isolated from ground motion by 2 highly damped bodies. 
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