Information of Column Design
The column is an important vertical structural member in the building that helps to transfer the load of the building to the foundation. It creates a framework that withstands all the load of the structure.
The columns are designed to resist the axial loads and the lateral loads and transfer them effectively to the foundation of the structure.
So, as all the loads from beams, slabs are transferred through the columns, it is important to design strong columns.
In this article, we will go through the detailed procedure of design of RCC column as per IS 456:2000. The column is defined as a compression member which has an effective length greater than its least lateral dimension.
Column length is three times the least lateral dimension of the cross-section. The main factors that govern the strength of the columns are their shape, size, and cross-section.
Design of RCC Column
Let us understand the column design procedure with one example
Design RCC column which is subjected to the axial load of 600 KN and the concrete used is of M-20 grade and steel Fe-500. Provide 1% steel and the factor of safety 1.5
Solution:
Fck = 20 N/mm2
FY = 500 N/mm2
Ag = Gross area of the column
Area of steel in concrete (ASC) = (1/100) x Ag
Area of concrete (Ac) = Gross area of column (Ag) – Area of steel (ASC) = Ag -0.01 Ag
Ac = 0.99 Ag
Pu = Axial load on column
Pu = load on column x Factor of safety
Pu = 600 x 1.5 = 900 KN
Following is the formula that is used for the design calculations of the RCC column for the building as per the IS 456:2000
Pu = 0.4 fck x Ac + 0.67 x FY x ASC
where,
Pu = Axial Load on the column
Fck = Characteristics compressive strength of the concrete
Ac = Area of concrete
FY = Characteristics Tensile strength of Steel
ASC = Area of steel reinforcement
Ac = Ag – ASC
ASC= 0.01 Ag
Ac = 0.99 Ag
Ag = Gross Area of Column
Consider 1% of steel in column
Ac = Ag – ASC
900 x 103 = 0.4 x 20 x (0.99Ag) + 0.67 x 500 x 0.01Ag
Ag = 79858 mm2
RCC Column Size Calculation
For the calculation of the RCC Column size it is necessary that we should know essential parameters of the factored load on the column, grade of the steel and concrete used in the column.
The size of the column is calculated as per the load coming on the column from the superstructure.
For the construction of the High Rise buildings, the size of the column is increased. The size of the column is a key factor that is considered for the designing of any structure.
Different sizes of the columns that are used in the designing of the buildings are as follows
- 9” x 9”
- 9” x 12”
- 12” x 12”
- 12″ x 15″
- 15″ x 18″
- 18″ x 18″
- 20″ x 24″
The minimum size of the column should not be less than 230 mm x 230 mm. The more size of the columns can also be used depending upon the structural loads.
For RCC Column size calculation following data is required.
- Grade of Concrete
- Grade of Steel
- Factored Load on Column
Shape of the column = square shape
Size of column = √ 79858 = 282.59 mm
So, providing the size of the column 285mm x 285mm
Gross Area provided = ( 285 mm x 285 mm ) = 81225 mm2
Area of steel provided in concrete (ASC) = 0.01 Ag
ASC = 0.01 x 81225
ASC= 812.25 mm2
Provide 8 nos 12 mm diameter of reinforcement bars having area of steel = 905 mm2
RCC Column Design
Diameter of lateral ties as per the IS 456:2000
- ¼ x Diameter of larger bars = ¼ x 12 = 3 mm
- 8 mm
Provide larger of the above two values that is provide 8 mm diameter of the lateral ties
The pitch of the lateral Ties as per the IS:456
- Least lateral dimension = 285 mm
- 16 x Diameter of the smaller reinforcement bars = 192 mm
- 300 mm
Provide smaller whatever is of the above three values
Provide pitch = 190 mm
Provide 8 mm diameter of lateral ties at the 190 mm of center to center distance.
FAQ: RCC Column Design
What Is an Rcc Column?
An RCC (Reinforced Cement Concrete) column is a vertical structural member designed to transfer the load from the superstructure to the foundation. It is reinforced with steel bars to enhance its strength and load-bearing capacity.
What Does Is 456:2000 Specify for Rcc Column Design?
IS 456:2000 provides guidelines for the design and construction of reinforced concrete structures. It includes criteria for load calculations, material specifications, and reinforcement detailing for RCC columns.
How Do You Determine the Size of an Rcc Column?
The size of an RCC column is determined based on the axial load it will bear, the grade of concrete and steel used, and the dimensions of the column’s cross-section. The column’s gross area is calculated to ensure it can safely carry the applied loads.
What Is the Significance of the Axial Load in Rcc Column Design?
The axial load is the primary load that an RCC column must support. It is crucial in determining the size and reinforcement of the column to ensure it can withstand the applied forces without failure.
How Is the Area of Steel Reinforcement Calculated?
The area of steel reinforcement is calculated as a percentage of the gross area of the column. For example, if 1% steel is required, the area of steel (ASC) is 1% of the gross area of the column.
What Factors Influence the Size of an Rcc Column?
The size of an RCC column is influenced by factors such as the magnitude of the axial load, the grade of concrete and steel, the column’s effective length, and the building’s design requirements.
How Do You Choose the Diameter of Lateral Ties for an Rcc Column?
The diameter of lateral ties is selected based on the diameter of the larger reinforcement bars used in the column. According to IS 456:2000, it should be a quarter of the larger bar’s diameter or a specified minimum size.
What Is the Typical Pitch of Lateral Ties in an Rcc Column?
The pitch of lateral ties is determined based on the column’s least lateral dimension and the diameter of the smaller reinforcement bars. It ensures proper confinement of the column’s core and effective load transfer.
Why Is It Important to Provide Sufficient Reinforcement in Rcc Columns?
Sufficient reinforcement is essential to resist the stresses and strains induced by axial loads, bending moments, and shear forces. It ensures the structural integrity and safety of the column.
What Should Be the Minimum Size of an Rcc Column?
The minimum size of an RCC column, as recommended by design codes, should not be less than 230 mm x 230 mm. Larger sizes may be used depending on the structural loads and design requirements.
