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?
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