**Iron rod/steel size for 9″×9″(230mm×230mm) rcc column | Rainforcement details of 9″×9″(230mm×230mm) size rcc column | which diameter of iron rod is suitable for 9″×9″(230mm×230mm) size rcc column | How to find out number of 12mm dia of iron rod in a 9″×9″ rcc column | How to find out dia of 4nos of iron rod in a 9″×9″ rcc column.**

**IS 456:2000 recommendation for designing of column**

1) minimum clear cover for column 40mm is provided, if size of column is less than 200mm then clear cover is 25mm is provided.

2) minimum diameter of bar 4 nos of 12mm should be taken

3) minimum area of Steel =0.8%of Ag

Maximum area of Steel=6%of Ag ( Steel should not overlap) 4%of Ag if steel is overlap

4) maximum spacing between two longitudes renforcement shall not greater than 300 mm

5) minimum dia of Stirrup 1/4×16 greater

6) maximum spacing of stirrup 16D, B and 300mm whichever is minimum.

**Iron rod/steel size for 9″×9″(230mm×230mm) rcc column**

Iron rod or steel size used for RCC column depending on load acting on column, Lateral forces, number of floor, alignment of column, span between two column and size of column.

The minimum iron rod/ steel in a 9″ x 9″ rcc column is 4 bars of 12mm with stirrups of 8mm steel rings at a distance of 150mm (6″) centre to centre of Fe500 grade of Steel and M20 grade of concrete ratio 1:1.5:3 are used and providing clear cover of 40mm.

**How to find out number of 12mm dia of iron rod in a 9″×9″ rcc column**

Generally, we provide steel reinforcement 1 to 2% of gross area of concrete inside RCC column for residential building.

We have given Gross area of concrete Ag=100%, suppose minimum 0.8% of steel is provided in a 9″×9″ rcc column for ground floor residential building, so steel area Asc=0.8%of Ag =0.008Ag, and concrete area Ac = 99.2% of Ag=0.992Ag.

Total Gross area Ag =230mm×230mm=52900mm2,

Suppose we are using 12mm dia of rebar in 9″×9″ size rectangular column, then how many dia of 12mm rebar required in a 9″×9″ size rectangular column?.

Formula we used, Ag = Ac +Asc, Asc=Ag-Ac,

Asc = 52900 – 0.992×52900, Asc = 52900 – 52476.8, Area of steel Asc =423.2mm2,

To find out number of 12mm dia of iron rod in a 9″×9″ rcc column, we used the formula, Area of steel Asc = n×πD2/4, Where n= number of iron rod, D = dia of rebar, π =3.14, putting all value in above mentioned formula, we get,

423.2mm2 = n ×πD2/4, 423.2mm2 = n ×3.14×12×12/4, 423.2mm2 = n ×113.04, Number of required iron rod n = 423.2/113.04 =3.74, taking in round figure 4nos of T12 rebar, so minimum 4nos of 12mm dia of rebar/iron rod is used in a 9″×9″ rcc column.

**How to find out dia/size of 4nos of iron rod in a 9″×9″ rcc column**

We use the formula, to find out dia of 4nos of iron rod in a 9″×9″ rcc column,

Area of steel Asc = n×πD2/4, where Asc= 423.2mm2, number of rebar =4nos and π=3.14, putting all value we get, Asc = n×πD2/4, 423.2 = 4 ×3.14×D2/4, D^2 = 423.2/3.14, Diameter of rebar D =√134.78mm2, Diameter of rebar D =11.60mm, taking in round figure as 12mm, so 12mm dia of 4nos of rebar/iron rod is used in a 9″×9″ rcc column.

**Rainforcement details of 9″×9″(230mm×230mm) size rcc column**

Generally, we provide steel reinforcement 1 to 2% of gross area of concrete inside RCC column for residential building.

We have given Gross area of concrete Ag=100%, suppose minimum 0.8% of steel is provided in a 9″×9″ rcc column for ground floor residential building, so steel area Asc=0.8%of Ag =0.008Ag, and concrete area Ac = 99.2% of Ag=0.992Ag.

Rainforcement details of 9″×9″(230mm×230mm) size rcc column:- The minimum iron rod/ steel reinforcement in a 9″ x 9″ rcc column is 4 bars of 12mm with stirrups of 8mm steel rings at a distance of 150mm (6″) centre to centre of Fe500 grade of Steel and M20 grade of concrete ratio 1:1.5:3 and providing clear cover of 40mm.