topic Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs. in Robot Structural Analysis Forum

First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

1584253 — Sun, 25 Aug 2019 17:11:32 GMT

Hi , I’m Italian student and this is my first model in this amazing software. Sorry for my english. I've lot of question, and glad to have your help.

Seismic analysis (i don't count eccentricy in analysis to avoid an increase of analysis time): Modes: much modes with low participating mass, so i can use 300 modes to reach 85% partecipating mass, because of:

Vertical action
Mixt structure reinforced concrete wall + column steel

Is this observations right? is it possible that a lumped mass matrix it's a wrong model in this case?

Cases: I create my SLE (SLS) and SLU (ULS) cases. But when i created Seismic Analysis, they appeared a lot of case that i don't know and im not able to delete: SLE:CHR; SLE:FRE; SLE:QPR what's that?
Load to mass conversion: I converted load into mass. I didn't pin Disregard Density, and i dont' convert into dynamic mass DL (Dead Load) is it correct?
Plate Foundation on winkler springs: I try to create a model with springs, but it too slow to work on it. So i prefered to use a fixed model, and analyze and rebar plate apart.
Now, how can i carry out stress and forces from column and Wall to my plate in another file to analyize my plate?
Plate Foundation Support: when i applied Springs, i noticed that i can define and applied elastic coefficent (Kz) in two different screens, first: in Thickness definition i can apply my elastic coefficent. Then in Support i can define my springs with Kz coefficent. Should insert Kz in all of this?
Thanks in advance.

Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

Simau — Mon, 26 Aug 2019 11:24:24 GMT

Hi @1584253

Each of the questions asked need a thread.

1) The vertical earthquake is mandotary only under certain conditions (according to the regulations). In average building Z direction is not taken into consideration and it is difficult to reach 85% for this direction.
Difficult to give an opinion on this point without a view of the structure.

2) Case: how did you generate the combinations, manual, automatic?

3) Load to mass conversion: Correct

4) Plate foundation: This thread may be useful
https://forums.autodesk.com/t5/robot-structural-analysis-forum/only-reaction-for-new-model-api/m-p/3659242

5) Plate foundations: use one of both, not both at the same time

Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

1584253 — Mon, 26 Aug 2019 12:51:38 GMT

Sorry for a unique message, it's for me important have a check about correct analysis and modelling. Next time i try to be more selective.

1) It's a mandatory for me, because of long cantilever and structure hanged a trusses.
I've attach my model.

2) I created manually ULS,SLS (SLE in my country). Then i've generated Seismic Analysis and it generate: Spectrum SLV,SLD in X,Y,Z Direction ecc.. and also it generate automatically Newmark combinations (Ex,Ey,Ez) but also generate strange combination like SLE:CHR SLE:FRE ecc..

4) thanks!

5) Thanks!

Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

Simau — Mon, 26 Aug 2019 18:57:53 GMT

I don't know really why you need 60cm thickness for walls. I reduce it down to 25 cm, and reach 85% with only 118 modes. Model attached

Could you send your model with sismique calculation?

Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

1584253 — Mon, 26 Aug 2019 19:38:02 GMT

So, greater difference between stiffness more modes I have to counting to reach 85%? Probably is it a matter of stiffness matrix size?

The wall was sized with some hand calculation with static lateral equivalent forces. Is only a pre-sized.

Ps: I'm exported forces on raft with API which you introduced. Thanks a lot!

Re: First Seismic Analysis. Chek result. Slab foundation on winkler Springs.

1584253 — Mon, 26 Aug 2019 20:56:31 GMT

Italy law is: DM2008.
the analysis sized 3.5Gb, so i can't attach it.