Detailing of reinforced concrete beam as per ACI Code

To make good design and execute the work in the construction site in a perfect manner, the detailing of the reinforced concrete members plays an important role.

The substandard detailing of reinforcement leads to the cracking of structure, extreme deflection, or even falling of the structure.

Reinforcements withstand tensile forces. They are also necessary in the compression zones to enhance the compression strength, improve ductility, decrease long-lasting deflections, or enhance the flexural strength for beams.

Besides, they resist cracking of concrete because of shrinkage and temperature stresses.

Given below, various features of reinforced concrete beam detailing on the basis of ACI Code

Types of reinforcement in a beam

1. Main bars (bottom steels)- handle tension force
2. Top bars (anchor bars)- retain stirrups in their position
3. Cut off bars- take care of tension forces
4. Stirrups with different spacing- deal with vertical and diagonal shear.

Hooked anchors: The act of hooked anchors is the provision of supplementary anchorage when there is insufficient straight length accessible to develop a bar.

Generally, standard hooks mentioned in ACI Code Section 7.1 applied aside from the case where it is particularly stipulated.

The ACI standard hooks are provided as follow: ACI standard hooks for primary reinforcement :-

1. 180-degree bend along with 4db extension, but not below 65 mm at free end of bar.
2. 90-degree bend plus 12db extension at free end of bar.

ACI standard hooks for stirrups

1. 16 bar and smaller, 90-degree bend along with 6db extension at free end of bar.
2. 19, No. 22, and No. 25 bar, 90-degree bend along with 12db extension at free end of bar
3. 25 bar and smaller, 135-degree bend along with 6db extension at free end of bar.

Lowest bend diameters: Standard bends in reinforcing bars are defined regarding the inside diameter of bend since the process is simple to calculate than the radius of bend.

The elementary factors which manage the minimum bend diameter are probability of bending devoid of breakage and evasion of crushing the concrete inside the bend.

Diameter of bend is calculated on the inside of the bar, except for stirrups in sizes No. 10 through No. 16, should not remain under the values provided in Table 1.

Inside diameter of bend for stirrups should not be under 4db for No. 16 bar and smaller. For bars greater than No. 16, diameter of bend should be compliant with Table 1.

Inside diameter of bend in welded wire reinforcement for stirrups should not be under 4db for deformed wire greater than MD40 and 2db for all other wires. Bends with inside diameter of under 8db should not remain below 4db from adjacent welded intersection.

In Table 1 lowest inside diameter of hooks is provided on the basis of the size of the bars.

Article Source: theconstructor.org