Multi-support excitation acceleration input

[naba077]

Hi,
I have a question that why multi-support excitation(sine-wave/earthquake wave) has only displacement input? Can we give multi support acceleration input? ( I'm referring to the Wiki examples; http://opensees.berkeley.edu/wiki/index ... _Sine-Wave). If yes, how can we do it?

[fmk]

you could but i do not reccomend it. the multi-support imposes displacements on the support nodes. if you only supply accelerations, we use a simple trapezoidal integration to come up with what those displacements are. depending on how the acceleration record is processed and filtered, this may not be what you want as it can result in drift over time in the resulting ground displacement.