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Standard Hooks, Seismic Hooks, Crossties, and Minimum Inside Bend Diameters per ACI 318-19 with ideCAD

How does ideCAD define standard hooks, seismic hooks, crossties, and minimum inside bend Diameters according to ACI 318-19?


db = nominal diameter of bar, wire, or prestressing strand, in

Standard hooks for developing 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 an inside diameter of less than 8db are not less than 4db from the nearest welded intersection according to 25.3

Seismic Hooks

Seismic hooks used to anchor stirrups, ties, hoops, and crossties in according to 25.3.4

  • Minimum bend of 90 degrees for circular hoops and 135 degrees for all other hoops

  • Hook engages longitudinal reinforcement, and the extension projects into the interior of the stirrup or hoop


According to 25.3.5

  • Crosstie is continuous between ends

  • There is a seismic hook at one end

  • There is a standard hook at the other end with a minimum bend of 90 degrees

  • Hooks engage peripheral longitudinal bars

  • 90-degree hooks of two successive crossties engaging the same longitudinal bars are alternated end for end unless crossties satisfy or

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