horizontal distribution of seismic forces

[nrguades]

I usually compute seismic forces manually, and apply it to my model. If I have a rigid diaphragm, I distribute the seismic force at each level based on a rigid diaphragm distribution, where the rigidity of the column or shearwall greatly matters.

In staad, where the program generated seismic forces is used, I observed that the horizontal distribution of the seismic forces, seems like, based on the defined weight on each node. The greater the weight covered by the node the greater the direct shear and torsion at that particular node. Any comments? thanks

 

[shaking]

WHAT YOU SAYiNG SOUNDS LiKE WHAT iT SHOULD BE. tHE GREATER THE MASS AT ANY PARTiCULAR FLOOR, tHE gREATER THE SESiMiC FORCE WiLL BE. i.E. THE ATTRACTED FORCE, AND HENCE THE SHEAR FORCE OF THAT STORY WiLL BE HiGHER.

KAMiL