All RCC columns, as per the code IS-456, shall be designed for minimum eccentricity, equal to the unsupported length of column/500 plus lateral dimension/30, subjected to a minimum eccentricity value of .................... mm.

 

 3)All RCC columns, as per the code IS-456, shall be designed for minimum eccentricity, equal to the unsupported length of column/500 plus lateral dimension/30, subjected to a minimum eccentricity value of .................... mm. 

ans - 20 mm

Concept

As per IS 456:2000, for RCC columns, the minimum eccentricity to be considered in the design is given by the following formula:

$$e_{\text{min}} = \frac{l_{\text{u}}}{500} + \frac{d}{30}$$

Where:

• $l_{\text{u}}$ is the unsupported length of the column.
• $d$ is the lateral dimension of the column (the smaller of the two dimensions).

However, IS 456:2000 also specifies a minimum eccentricity value of 20 mm.

This means that, regardless of the result from the above formula, the minimum eccentricity should not be less than 20 mm.

Let me know if you'd like more details!