Why the Diameter of Reinforced Concrete Should Not Be Reduced from Structural Drawings

In reinforced concrete construction, structural drawings are not merely guidelines, but the result of precise technical calculations. One mistake that is still frequently made in the field is reducing the diameter of the rebar from that specified in the structural drawings due to efficiency or material limitations.

However, changing the diameter of the rebar can seriously impact the strength, safety, and lifespan of the building. Here's an explanation of why this practice should not be done.

1. Rebar Diameter Determines the Tensile Strength of the Structure
Rebar functions to withstand tensile forces that concrete cannot withstand. The larger the diameter of the rebar, the greater the:

• Reinforcement Cross-sectional area
• Tensile force capacity
• Reducing the diameter directly reduces the structure's load-bearing capacity, which is invisible to the naked eye.

2. Structural Calculations Have Been Adjusted to the Load
Each rebar diameter in the structural drawings has been calculated based on:

• Dead load
• Live load
• Seismic and wind loads
• Safety factor

Changing from Ø13 mm to Ø10 mm, for example, would render the structure inconsistent with the initial calculations and risk failing to meet safety standards.

3. Increased Risk of Cracking and Deflection
Smaller diameter rebar will cause:

• Concrete cracks more easily
• Beam and slab deflection increases
• Load distribution is suboptimal

In the long term, this condition can reduce the comfort and function of the building.

4. Decreased Bonding Strength of Concrete and Reinforcement
The diameter of the rebar also affects the bonding strength between the concrete and the rebar. If the diameter is reduced:

• Tensile forces are not properly transferred
• Slippage occurs between the rebar and concrete
• Structural performance decreases

As a result, the structure does not function as a solid unit.

5. Eliminating the Structural Safety Factor
Structural drawings are always designed with a certain safety factor. Reducing the diameter of the rebar means eliminating the reserve strength that should protect the structure from extreme conditions.

In situations of excessive loads or earthquakes, the risk of damage will increase drastically.

6. Cannot Be Replaced by Increasing the Number of Rebars Without Calculation
The assumption that a small diameter can be compensated for by increasing the number of rebars is also wrong if it is not recalculated. These changes can:

• Disrupt the spacing of the reinforcement bars
• Complicate casting
• Decrease the quality of the concrete

All changes to the reinforcement bars must be recalculated by the engineer.

Conclusion
The diameter of the rebar in the structural drawings must not be reduced because it:

• Reduces the tensile strength of the structure
• Eliminates the safety factor
• Increases the risk of cracking and failure
• Under-calculated material efficiency can actually result in significantly higher repair costs.

Use Rebar According to Structural Specifications
PT Intisumber Bajasakti provides quality rebar, meeting SNI standards, with complete sizes to support the structural requirements as per the working drawings.

📞 Phone: 021-66675999
🌐 Web: intisumberbajasakti.com
✉️ Email: info@intisumberbajasakti.com

Contact our team now to obtain rebar according to your specifications and consult on your project's material needs.

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