As per IS 456:2000, when the depth of the web in a RCC beam exceeds 750 mm, the side face reinforcement will NOT be less than_______ of the web area
0.1%
IS 456:2000 Side Face Reinforcement in RCC Beams
As per the Indian Standard code IS 456:2000, which provides the plain and reinforced concrete code of practice for general building construction, specific rules apply to the design of RCC beams, especially concerning their dimensions and the required reinforcement. One such important provision deals with side face reinforcement in deep beams.
RCC Beam Web Depth Requirement
When an RCC beam has a large depth, specifically when the depth of its web (the vertical part of the beam) exceeds 750 mm, it becomes more susceptible to certain types of cracking. To control these cracks, the code mandates the inclusion of additional steel reinforcement on the side faces of the web.
Side Face Reinforcement Requirement as per IS 456:2000
Clause 26.5.1.3 of IS 456:2000 specifies the requirement for side face reinforcement.
- If the depth of the web in a beam exceeds 750 mm, side face reinforcement must be provided.
- The total area of this side face reinforcement should not be less than \(0.1\%\) of the web area.
- This reinforcement should be distributed equally on both faces (sides) of the web. This means \(0.05\%\) of the web area on each side.
- The spacing of this reinforcement should not exceed 300 mm or the web thickness, whichever is less.
Minimum Reinforcement for Cracking Control
The primary purpose of providing this minimum reinforcement on the side faces is to control the formation of cracks. These cracks can occur due to factors like shrinkage of concrete (as it dries and hardens) and temperature variations, especially in large volumes of concrete found in deep beams. Without adequate side face reinforcement, these cracks could become wide and affect the durability and aesthetic appearance of the structure. The \(0.1\%\) provision ensures sufficient steel to counteract these tensile stresses.
Conclusion
Therefore, as per IS 456:2000, when the depth of the web in an RCC beam exceeds 750 mm, the side face reinforcement must be not less than \(0.1\%\) of the web area.
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