Hi every one i have modelled staad with same number of columns and all the column sizes are same. so as per the staad literature the stiffness of columns calculated as 12EI/L^3. My member sizes are same and the floor heights are same in staad but the story stiffness is not same. It changes from story to story pls help?
There may be other lateral force resisting elements in your structure besides the columns that may be causing this variation.
There are no lateral resisting elements in my structures other than columns no shear walls retaining walls etc. It is purely R.c.c beam column structure