Hi,
I created model 4 stories and its symmetric 100% in both directions. I did 2 Seismic Cases
The first one is not with eccentricity (Case 28) the results of reduced torsion on the stories was about 0 which is correct because the building is totally symmetric (i.e the center of gravity and center of rigidity are in same coordinates ).
The second case with eccentricity 2m (Case 30 the results of reduced torsion in the stories came very huge instead of being only the value of (Fx * 2m )
Hi @ mustafahesenow
IMHO that you have two seismic cases (W / WO ) additional eccentricity then (only one Model case ) should be defined instead of two as shown in the picture below .
Once you do that the results will be as you are expected .
The file also attached
Refaat
Hi @Refaat
When we consider the eccentricity from the seismic case the torsion moment will be calculated correctly. but when we choose the eccentricity from the modal it will affect even the modal result to to shift or add more mass . The issue now the torsion should be the eccentricity multiple by the force but the result came very huge .
My point is As you see if we consider the eccentricity from modal the result will change not same if we consider this eccentricity from the seismic force.
Please be noted that also that when the modal will have eccentricity the eccentricity option in the corresponding seismic force will be hidden.
Hi @mustafahesenow and @Refaat
In RSA there are two ways of defining eccentricity for the response spectra analysis. The simplified approach (see Simplified method for defining eccentricities topic) and the more accurate solution based on increase of mass on one side of a structure and decreasing it on the opposite one). For the prior MZ is indeed FX * eccentricity by its principle however I have difficulty due to my limited knowledge of seismic analysis to tell if the results obtained for the later are correct or wrong (too large MZ) as shapes of modes in case 29 are obviously different than these obtained for case 27. 
In both of the 2 ways of defining the eccentricity from the modal parameters the results of MZ are closed to each other but they are very huge than the expected once The resultant eccentricity is about (6m) but the defined one is 2m.
Any news about this topic ?
Hi Mustafa,
It is still under the investigation. My assumption is that this is due to the results of the modal analysis with masses as assigned to the nodes of the model. If I may ask you what in your opinion should be the value of mass in each of these 3 nodes after defining 2 meters mass offset?
Sorry for late reply. I didnt understand your question Can you please explain it more.
