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

[1584253]

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:

1. Vertical action
2. 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.

[Simau]

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/3...

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

[1584253]

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! 

[Simau]

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?

[1584253]

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!  

[1584253]

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