@Anonymous
Maybe I was not clear enough, sorry
Firstly i'm relay interested, if it is necessary to have 60 or more modes for 2-story building?
it is not a matter of number of modes, the goal is to know if the number of mode retained is sufficient to estimate the efforts in the part of the structure which interests you.
In this case, it is the upper part of your structure that is sensitive to earthquakes. In the model (sous-structure) of this part alone, you can see that mobilized mass is almost 100% in X and Y with only with 7 modes.
It would be good if you compare the efforts in some elements of the high part obtained with 7 modes in these models with and without the lower part.
Secondly, i can't find mobilized mass (82%) in mode 2, and which direction we're talking about? Can you show me where is it, please.
The 80% in mode 2 are related flexible structure only without the lower part, see attached file in post 7.
It'd be great if you advice me some manuals about this topic, so that i could read it.
see attached file (in French :0( )
M. Agayr
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