Anchorage of Tension Bars By Hook

Standard Dimension:

The desire tensile stress in a bar cannot be developed by bond alone.so it is important to provide a special anchorage of a bar at the end of the bar. Normally it is 90° or a 180° hook or a headed bar. According to ACI code 7.1, the dimensions and bend radii for hooks have to determine. The ACI code 7.1 is as follows

1. A 180° bend plus an extension of at least 4 bar diameters, but not less than 2.5in. At the free end of the bar Or
2. A 90° bend plus an extension of at least 12 bar diameters, but not less than 2.5in. At the free end of the bar
3. For stirrup and tie anchorage only

(i) for #5 (16mm) bars and smaller, a 90° bend plus an extension of at least 6 bar diameters at the free end of the bar or

(ii) for #6,#7,#8 (19mm,22mm,25mm) bars, a 90° bend plus an extension of at least 12 bar diameters at the free end of the bar or

(iii) For #8 (25mm) bars and smaller, a 135° bend plus an extension of at least 6 bar diameters at the free end of the bar.

The Minimum diameter of a bend, measured on the inside of the bar.

Standard hooks other than for stirrups or ties in sizes between #3 through #5 (10mm through 16mm) should be not less than the values from the below Table (Table-1).

Table-01

Minimum diameters of Bend for Standard Hooks

Bar Size	Minimum Diameter
#3 to #8 (10mm to 25mm)	6 bar diameter
#9 ,#10,#11 (29mm , 32mm,36mm)	8 bar diameter
#14 & #18(43mm,57mm)	10 bar diameter

For stirrup and tie hook, for bar sizes, #5 (16mm) and smaller the inside diameter of the bend should not be less than 4 bar diameters, According to ACI code.

Figure: Standard Bar Hooks For Main reinforcement

Figure: Standard Bar Hooks For Stirrups and ties reinforcement

Source: Design of Concrete Structures by Arthur H. Nilson, David Darwin, Charles W. Dolan (14 Edition)