Good morning,
I am wondering if the compliant base at the horizontal base of the model is capable or not to dissipate also downward waves with both horizontal and vertical direction (model with horizontal line displacement for the horizontal component of the ground motion applied at the base and fixed vertical displacement at the base).
Has anyone tried to run a dynamic analysis applying, instead of the fixed vertical displacement for the base, a vertical accelerogram with zero amplitudes?
Thank you in advance,
Andrea Balia
Dear Andrea,
The compliant base will indeed dissipate downward waves. In fact, that is the main reason why the compliant base boundary condition exists since a "regular" boundary conditions with a prescribed displacement cannot disspitate downward waves due to the prescribed displacements.
With respect to part 2 of your question....I have never tried, but I wouldn't immediately see the reason for it. If this is related to your question whether a compliant base will dissipate downward waves: yes it will, always. Independent of whether a vertical acceleration is assigned or not and whether that vertical acceleration is zero or has values.
With kind regards,
Dennis Waterman
Dear @dennis waterman what is the reason for selecting 0.5 for u start with the compliance base?
Dear Jamal,
The waves measured contains both upwards and downward motion waves, but in the project only the upward motion should be applied. We assume that the upward motion is half the total measured signal, hence u = 0.5.
This is very helpful, thank you.
Dear Dennis Waterman,
Thank you for the information. I was wondering if we can select compliant base and set u=1.0m instead of u=0.5 (as far as I understood, the reason to use u=0.5 is for outcropping motions.
For a case where all my input motion has been selected from PEER ground motions database and scaled appropriately to reflect my site conditions, will I be able to use compliant base u=1.0m.
If you have data that is indeed only upward motion data you can use u=1.0. I'm not so sure though that PEER data is upward motion data, so you would have to check that.
Thank you again, Mr. Dennis.