asdeasoft.net

Dear STKO team,

I found a document in FLAC3D talking about the input acceleration at the base of soil model.
It said that EQ motion is generated by tau=2*Vs*rho*v. the factor of 2 accounts for the fact that the applied stress must be double that which is observed in an infinite medium, since half the input energy is absorbed by the viscous boundary.
(Reference: http://docs.itascacg.com/flac3d700/flac ... tions.html)

But when I read some example in Opensees webpage, they set tau=Vs*rho*v.

I have 2 questions:
1/ I am wondering what you did in ASDAborsing boundary condition? tau=2*Vs*rho*v or tau=Vs*rho*v
Because in my model, I used deconvolution process to obtain bedrock motion, then apply 0.5velocity to my 3D model. some motions give a matching between record and simualation, while others give a bad matching (simulation is a half of record).

2/ What velocity should I use to apply at the base of soil domain? 1*velocity or 0.5*velocity?

thank for support.
Buu

Regardless of which method you use to obtain the input at the base, you need to apply exactly the velocity you want to see there.
The ASDAbsorbing element takes care of multiplying the input by 2, to account for the half of it being absorbed by the dashpots: Then it depends on what the software for deconvolution gives you.