Standard Hooks, Seismic Hooks, Crossties, and Minimum Inside Bend Diameters
db = nominal diameter of bar, wire, or prestressing strand, in
Standard hooks for the development of deformed bars in tension should conform to Table 25.3.1.
Minimum inside bend diameters for bars used as transverse reinforcement and standard hooks for bars used to anchor stirrups, ties, hoops, and spirals should conform to Table 25.3.2. Standard hooks are enclosed longitudinal reinforcement.
Welded Wire Reinforcement
Minimum inside bend diameters for welded wire reinforcement used as stirrups or ties is not less than 4db for deformed wire larger than D6 and 2db for all other wires. Bends with inside diameter of less than 8db is not less than 4db from nearest welded intersection according to 25.3
Seismic hooks used to anchor stirrups, ties, hoops, and crossties is in according to 25.3.4
(a) Minimum bend of 90 degrees for circular hoops and 135 degrees for all other hoops
(b) Hook engage longitudinal reinforcement and the extension projects into the interior of the stirrup or hoop
According to 25.3.5
(a) Crosstie is continuous between ends
(b) There is a seismic hook at one end
(c) There is a standard hook at other end with minimum bend of 90 degrees
(d) Hooks engages peripheral longitudinal bars
(e) 90-degree hooks of two successive crossties engaging the same longitudinal bars is alternated end for end, unless crossties satisfy 126.96.36.199 or 188.8.131.52.1