Minimum Reinforcement for Drift

The option to apply two-way shear minimum reinforcement code provisions for seismic drift as found in ACI 318-14 Section 18.14.5.1 is given in the Criteria ribbon Shear Design options window.

Click on image to enlarge

The referenced provision is found in the excerpt below. Note that the provision is conditional upon a check of the inter-story drift ratio at the support location. The program does not check this drift ratio but gives you the option to directly enforce a minimum shear strength of 3.5*√f’c.

From ACI 318-14

Click on image to enlarge

The current expressions used to calculate As for two-way shear are shown below as taken from ADAPT-Technical Note TN504 . If the Apply minimum reinforcement for drift requirement is selected, the program checks this requirement only if reinforcement is required at that critical section. The program checks that the quantity in the parentheses is ≥ 3.5*√f’c for all critical sections within a distance of 4*slab thickness from the face of support.

Additional checks with respect to Av,min still apply as shown below.

Click on image to enlarge