Tips to design hooks with ACI codes & different sizes of hooks

This is a short video tutorial for civil engineering students presented by the renowned engineer S.L. Khan.

In this construction tutorial, you will be familiar with the standard sizes of the rebar hooks as well as the method required for designing hooks with ACI codes.

The hooks are arranged in beams and columns for the following purposes :-

1. To protect from buckling
2. To avoid from spreading.
3. To protect concrete from parting outside
4. To retain longitudinal steel bars in proper location

It is known that the required tensile stress can’t be developed with the bond separately.

To get rid of the issue, the special anchorage is arranged at the ends of the bar in the form of a 90 degree , a 180 degree or a headed bar.

The bend radii and dimensions for hooks are organized in ACI code 7.1

The considerations should be given on the following points :-

1) With adherence to ACI A 180 degree bend along with an extension of minimum 4 bar diameters, but not under 2 ½ inches at the free end of the bar.

2) A 90 degree bend along with an extension of minimum 12 bar diameters at the free end of the bar.

According to ACI

For No.5 (No 16) bars and smaller, a 90 degree bend along with an extension of minimum 6 bar diameters at the free end of the bar should be arranged.

For Nos. 6, 7 and 8 (No. 19,22 and 25) bars, a 90 degree along with an extension of minimum 12 bar diameters at the free end of the bar should be arranged.

For No,8 (No 25) bars or smaller a 135 degree bend along with an extension of minimum 6 bar diameters at the free end of the bar should be arranged.

Keep in mind that the minimum diameter of bend calculated on the inside of the bar, for standard hooks except for stirrups or ties in sizes Nos.3 through 5 (Nos 10 through 16) should not be under the values demonstrated in the following table.

The table is extracted from a nice book “ design of concrete structures” written by Nilson. With adherence to ACI code for ties and stirrup hooks, the inside diameter of bend should not be under 4 bar diameters for bar size No 5 (No16) and smaller.

When welded wire reinforcement is employed for stirrups or ties, the inside diameter of bend should not be under 4 wire diameters for deformed wire greater than D6 and 2 wire diameters for all other wires. Bends containing an inside diameter of below 8 wire diameters should not remain under 4 bar wire diameters from the adjoining welded intersection.

To get more detail, watch the following video tutorial.

Video Source: SL Khan