Multiple Anchors Work As Group for Side
Blowout Check Along Depth Edge

ACI 318-11 D.5.4.2

When s11 <= 6c , edge anchors work as a group.
Nsbg = [1+ s /(6c) ] x Nsb

where    s = s1    s11= s1 / (nbd-1)   
             c = min(c2 , c4)


ACI 318-11 D.5.4.2