Evaluation of torsional moment due to the eccentricity between center of mass and center of stiffness

Step 4) Run the analysis without considering inherent eccentricity.

As shown in Screenshot

Step5) Go to Results tab -> results table-> story-> story eccentricity

Step6 ) Copy the Ecc. Dist. From the tables and paste it into the story data tab. 

Step7) check on the inherent eccentricity option in static seismic cases

Now you will be able to see the results including the inherent eccentricity.

- Could you also highlight the differences respect to the case in which the the floor diaphragm is considered?

When floor diaphragms are considered, the total seismic force is applied at the Center of mass of the floor as shown in the screenshot below

When floor diaphragms are not considered the total seismic force is applied at each node of the floor as shown in screenshot below

(I am supposing in this case the total seismic force applied in the center of mass is equally distributed at each node of the floor

and the torsional moment is distributed at each node according a sort of "equation of rotational equilibrium")

Yes, when we do not consider the floor diaphragm the total seismic force is transmitted to each node of the floor, and the torsional moments are distributed at each node according to the equation of rotational equilibrium. 

I think I was able to answer all the questions, kindly let us know if any further assistance needed.

Regards,
Anmol Saxena
Technical Support Engineer

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