I have a 6-story braced frame building with offset floors. When analyzed, a few frame shears decrease in force from 3rd floor to 2nd floor which causes a negative change in frame shear. What causes the decrease in force to happen? Do other frames attract more load due to stiffness? Is the decrease in force a result of higher modes?
If this shear reversal is acceptable, how is the diaphragm analyzed? Is there a large spike in shear at the reversal location?
Please see the attached PDF for clarification.
[View:/cfs-file/__key/communityserver-discussions-components-files/5932/Negative-Change-in-Frame-Shear.pdf:940:0]