pseudo- vs relative velocity

[jiao]

I have problem understanding the difference between pseudo-velocity and relative velocity response in seismic response.
Can anyone give me a hint?
Thanks

 

[tomirvine]

The most direct response parameter in seismic response calculations is relative displacement between the mass and the moving base. Note that the relative displacement is also the spring strain displacement.

Pseudo-velocity is the maximum relative displacement multiplied by omega, where omega is the natural frequency in (radians/time).

The pseudo velocity is nearly equal to the maximum relative velocity for systems with moderate or high frequencies (short periods) but may differ considerably from the maximum relative velocity for very low frequency systems (long periods).

Reference: Harris, Shock and Vibration Handbook

Sincerely, Tom Irvine

http://www.vibrationdata.com