db = nominal diameter of bar, wire, or prestressing strand,
Standard hooks for the development of deformed bars in tension should conform to TSC 22.214.171.124.
Seismic Hooks and Crossties
Minimum inside bend diameters for bars used as transverse reinforcement and seismic hooks for bars used to anchor stirrups, ties, hoops, and spirals should conform to TSC 126.96.36.199. Standard hooks are enclosed longitudinal reinforcement.
Special seismic hooks should have 135 degree curved hooks at both ends.
For seismic crossties, 90 degree curved hook can be made at one end. In this case, on one face of the column or shear-wall, crossties with hook bends of 135 degrees and 90 degrees will be arranged in staggered horizontal and vertical directions.
Inside bend diameter of 135 degree curved hooks should be at least 5db.