In an RCC beam, side face reinforcement is provided if its depth exceeds:
750 mm
RCC Beam Side Face Reinforcement Explained
In reinforced concrete (RCC) beams, providing adequate reinforcement is crucial for structural integrity and durability. One specific type of reinforcement is "side face reinforcement," which is particularly important for deep beams. The primary purpose of side face reinforcement is to control the formation of cracks caused by shrinkage and temperature variations, especially in the web (or side faces) of a deep beam. These cracks can occur when the concrete dries and shrinks, or when it experiences significant temperature changes, leading to tensile stresses.
Reinforcement Requirements as per IS 456:2000
The Indian Standard Code of Practice for Plain and Reinforced Concrete, IS 456:2000, provides clear guidelines on when and how side face reinforcement should be provided.
- Depth Criterion: As per Clause 26.5.1.3 of IS 456:2000, side face reinforcement must be provided in the web of a beam if its depth (d) exceeds 750 mm. This means for beams deeper than 750 mm, side face reinforcement becomes mandatory.
- Purpose: This reinforcement helps in controlling the width of cracks that might otherwise form due to shrinkage and temperature effects in such deep sections.
- Minimum Area: The total area of side face reinforcement should not be less than 0.1% of the web area. This reinforcement is distributed equally on both faces of the beam.
- Placement: This reinforcement should be distributed uniformly between the main tension reinforcement and the compression reinforcement (or top reinforcement, if present).
Calculation of Side Face Reinforcement Area
Let's consider a beam with web width \(b_w\) and overall depth \(D\). The total area of side face reinforcement (\(A_{sf}\)) is calculated as follows:
Total area of side face reinforcement,
\(A_{sf} = 0.1\% \text{ of web area}\)
\(A_{sf} = \frac{0.1}{100} \times b_w \times D\)
This total area \(A_{sf}\) is then divided equally between the two side faces of the beam. So, the area of reinforcement on each face would be \(\frac{A_{sf}}{2}\).
| Beam Depth Criterion | Side Face Reinforcement Requirement | Minimum Area Provided |
|---|---|---|
| Depth (d) > 750 mm | Mandatory | 0.1% of web area, distributed equally on both faces |
Importance of Side Face Reinforcement
- Crack Control: It primarily controls cracking due to drying shrinkage and thermal stresses, which are more pronounced in deep sections.
- Structural Integrity: By controlling crack widths, it helps maintain the long-term durability and serviceability of the beam. Excessive crack widths can lead to corrosion of main reinforcement and aesthetic issues.
- Shear Capacity: While its primary role is crack control, it also contributes marginally to the shear capacity of the beam.
Therefore, when the depth of an RCC beam exceeds 750 mm, providing side face reinforcement as per IS 456:2000 is a mandatory design consideration to ensure the beam performs adequately under various environmental and loading conditions.
Important Questions from Torsion
Additional longitudinal reinforcement is provided at faces if depth of member subjected to torsion exceeds _______ mm.
As per IS:456-2000, the side face reinforcement should be provided along the two faces of a beam, when the depth of the web in a beam exceeds
Determine the equivalent nominal shear stress in a rectangular RCC beam of 200 mm width and 400 mm effective depth if the shear force is 8 kN and torsional moment is 2 kN-m at factored loads.
