Side face reinforcement – IS 456:2000 (Indian Standard)

The side face reinforcement in structural elements, particularly beams, is required to control crack widths due to lateral shear forces and to prevent the sides from cracking under load. The provision of side face reinforcement is mandatory when the depth of the beam exceeds a certain limit, as specified by the relevant design codes, such as IS 456:2000 (Indian Standard) or other international standards.

Here’s a general procedure for calculating side face reinforcement based on IS 456:2000.

Step-by-Step Procedure for Side Face Reinforcement Calculation:

1. Check the Depth of the Beam:

• As per Clause 26.5.1.3 of IS 456:2000, side face reinforcement is provided when the depth of the web (effective depth d) exceeds 750 mm.
• If the effective depth (d) is less than 750 mm, side face reinforcement is not required.

2. Determine the Percentage of Side Face Reinforcement:

• According to IS 456:2000, when the effective depth d > 750 mm, the area of side face reinforcement on each side should not be less than 0.1% of the web area.
• The web area is calculated as:

Aweb​=D×b

Where:

• D = Effective depth of the beam
• b = Width of the beam

3. Calculate the Minimum Area of Side Face Reinforcement (A_s):

The total area of reinforcement on each side will be:

As=0.001×Aweb

As​=0.001×D×b

4. Distribution of Reinforcement:

• The side face reinforcement should be uniformly distributed along the height of the beam.
• Bars of diameter between 8 mm to 12 mm are typically used for side face reinforcement.
• The spacing of the side face reinforcement bars should not exceed 300 mm.

Example Calculation:

Let’s assume the following dimensions for a beam:

• Width (b) = 300 mm
• Effective depth (D) = 1000 mm (which is > 750 mm, so side face reinforcement is required)

1. Web Area:

Aweb=D×b=1000 mm×300 mm=300,000 mm2

Minimum Area of Side Face Reinforcement:

As=0.001×300,000=300 mm2

This means that a minimum of 300 mm² of reinforcement should be provided on each side of the beam.

5. Selection of Bars and Spacing:

• If you use 10 mm diameter bars (cross-sectional area of each bar = 78.5 mm²): Number of bars=300 / 78.5≈4 bars
• The bars should be spaced equally along the height of the beam, ensuring a maximum spacing of 300 mm between them.

Summary:

• For beams with effective depth > 750 mm, side face reinforcement is required.
• The minimum reinforcement on each side should be 0.1% of the web area.
• The reinforcement should be distributed evenly, typically using 8-12 mm diameter bars with a maximum spacing of 300 mm.

This ensures that the side face of deep beams is adequately reinforced to control cracking.

Side face reinforcement – American Concrete Institute (ACI) Code (ACI 318)

In the American Concrete Institute (ACI) Code (ACI 318), side face reinforcement is addressed for beams that have significant depth, primarily to control cracking on the side faces due to shrinkage, temperature variations, or lateral pressure. Here’s a detailed procedure for side face reinforcement calculation as per ACI 318-19.

ACI 318-19 Code Reference for Side Face Reinforcement:

• ACI 318-19 specifies side face reinforcement requirements in Section 9.7.2 for deep beams.
• Side face reinforcement is required when the overall depth (h) of the beam exceeds 36 inches (914 mm).

Procedure for Side Face Reinforcement Calculation:

1. Check Beam Depth:

• Side face reinforcement is required if the overall depth (h) of the beam exceeds 36 inches (914 mm).
• If h ≤ 36 inches (914 mm), side face reinforcement is not mandatory.

2. Area of Side Face Reinforcement:

• If h > 36 inches (914 mm), side face reinforcement is required and must not be less than 0.1% of the web area on each side of the beam.

The web area is calculated as:

Aweb=d×b

Where:

• d = Effective depth of the beam (distance from top to tension steel)
• b = Width of the beam

3. Minimum Area of Side Face Reinforcement (A_s):

• The minimum area of side face reinforcement is given by:

As=0.001×Aweb

As​=0.001×d×b

Where:

• A_s = Area of reinforcement on each side of the beam
• d = Effective depth of the beam
• b = Width of the beam

4. Distribution of Side Face Reinforcement:

• Side face reinforcement must be uniformly distributed over the depth of the beam.
• The spacing of the reinforcement must not exceed 12 inches (300 mm).

Example Calculation:

Assume you have a beam with the following dimensions:

• Width (b) = 400 mm (15.75 inches)
• Effective depth (d) = 1000 mm (39.37 inches) (greater than 914 mm, so side face reinforcement is required)

1. Web Area:

Aweb=d×b=1000 mm×400 mm=400,000 mm2

2. Minimum Area of Side Face Reinforcement:

As=0.001×400,000=400 mm2

This means that a minimum of 400 mm² of reinforcement should be provided on each side of the beam.

5. Selection of Bars and Spacing:

• If you choose 10 mm diameter bars (cross-sectional area of each bar = 78.5 mm²): Number of bars=400/ 78.5≈5 bars
• The bars should be spaced uniformly, and the spacing should not exceed 300 mm (12 inches).

Summary of Requirements (as per ACI 318-19):

• Side face reinforcement is mandatory when the beam depth exceeds 36 inches (914 mm).
• The minimum reinforcement on each side is 0.1% of the web area.
• Reinforcement should be distributed uniformly with a maximum spacing of 12 inches (300 mm).
• Bar diameters of 8 to 12 mm are typically used, depending on the design requirements.

This ensures that the side face of deep beams is sufficiently reinforced to control cracking and maintain structural integrity.