Opensees Drift calculation

[jonade]

I was trying to record drift for different excitation patterns with the same acceleration time series, uniform excitation and multi-support excitation. I know the recorder uses absolute displacement for multi-support excitation and relative displacement for uniform excitation but shouldn't the drift be the same for the two excitations? I am having different drift results for the two excitations even though I am using the same acceleration time series and I am not sure which one to use.

[jonade]

The multiple support excitation results were way above expected. The uniform excitation though gave reasonable results. After thoroughly checking everything I have found the reason for such a difference. I imported my model from sap2000. In sap2000 mass is assigned to the support and this mass was the reason for the difference between uniform excitation and multiple support excitation. Even though mass is assigned to the supports uniform excitation gives out reasonable results but multiple support excitation doesn't. I am not sure why assigning mass to the support affects multiple support excitation but when i deleted the support mass and compare the two results from uniform and multiple excitations the two results matched.