SHEAR WALLS IRREGULAR DISTRIBUTION

[SAYATTIA]

GENTLEMEN:
I AM DOING AN ETABS MODEL WITH ( SHEAR WALLS IRREGULAR DISTRIBUTION ) DUE TO ARCH, DESIGN.
A BIG ECCENTRICALLY VALUE BETWEEN CENTER OF RIGIDITY AND CENTER OF MASS IS RESULTED.
DO I HAVE TO CONSIDER THE ECCENTRICALLY VALUE WHILE CALCULATING SEISMIC FORCES ( BY AUTOMATIC SEISMIC FORCE CALCULATION ) OR IT WILL BE CONSIDERED AUTOMATICALLY BY THE PROGARM?

 

[slickdeals]

ETABS automatically calculates the additional torsional shears due to difference in CR and CM. I would define the diaphragm as semi-rigid to make sure proper in-plane diaphragm stiffness is accounted for.

 

[SAYATTIA]

would you explain in more details how etabs calculates the torsion due to eccenercity. do i have to identify any parameters to do that.

 

[slickdeals]

No, you don't have to do anything more than accurately modeling the locations/stiffness of the elements and the applied loads on the building.

Once the analysis is complete, you can see that the program has calculated a diaphragm center of rigidity and center of mass and the associated eccentricities.

 

[SAYATTIA]

GENTLEMEN:
I HAVE APPLIED SEISMIC LOADS ACCORDING TO UBC-97 ( AUTO LATERAL LOADS). WITH DIFFERENT ECCENERCITIES VALUES BY ADDING
AND/OR DELETING WALLS TO CHANGE THE POSITION of center OF RIGIDITY.the results load values ( T ,Mx and My) are still the same. i think that we have to apply manually the eccentercity value at each floor.
would you advise once again

 

[yahiatata]

HI,My probleme's :can i find the code seismic who elimine the first or the second mode the torsion axes Z.