Column size for 2 storey and 3 storey building | civil engineering | building design

Column size is the dimensions of the members considered in the structure. Basically column is the major component in the structure and it is the vertical member used to transfer the vertical loads from the beam to foundation. In this article you will able to learn about what are the dimensions of the column are considered for two storey and three storey building structures with different cross sections like square column shape, rectangular column shape and circular column shapes .

Factors effecting on the column sizes in the structure

The below specified are the major factors to be considered in the column design

1. Number of floors
2. Loading condition
3. Center to center distance between the columns

If the number of the floors increases for the structure then we have to provide higher dimensions of the columns in order to resist the load. Loading condition is the important factor we have to consider in the structure. In the structural design the loading condition is directly proportional to the column size.  For some building cases we will apply only gravity loads (Dead load and Live load) and for some buildings we will apply loads which are the combination of gravity (Dead load and Live load) and lateral loads (Seismic load and wind load). If the loading increases the column size is also increases and in the same process if the loading decreases then the column size is decreases. And lastly the main important factor is center to center distance between the columns. As per is code provisions the minimum center to center distance is 3m and maximum is 5m. If the value of center to center increases then the dimensions of the columns are also increases.

Basic parameters considered in the designing of columns

The following are the basic considerations assumed before column design

1. Minimum of 4 bars are considered in the column section.
2. Mostly give initial priority to the square column section, if not give second priority for the rectangular or polygon or circular sections.
3. The least dimensions of the columns are considered as 9”X9” (230mmX230mm).
4. The least diameter of the reinforcing bar is taken as 12mm.
5. Try to use same dimensions of the columns from the bottom storey to top storey.
6. The value of the concrete cover should be considered in between 25-50mm.
7. The concrete grade should be used as at least M20 grade.
8. The minimum value of center to center distance between the columns is taken as 3m and the maximum of 5m.
9. Lateral ties should be placed at the distance of 100mm distance.

Major Column Shapes of the columns used in the structures

According to IS code provisions it was suggested that for the structure we have to give initial priority for the square column section.  Majorly in most of the cases the below specified shape columns are used.

1. Square column
2. Rectangular column
3. Circular columns
4. Polygon columns (Example : Pentagonal shape, hexagonal shape)

Square columns

The columns which are having same dimensions for the all four sides we can call it as square columns.  For the square column section the value of eccentricity will be less because the load will be acts at the center of the section in square column. The minimum number of reinforced bars required for square columns are considered as 4 as per the IS code standards.

Rectangular columns

The columns which are having different dimensions for the opposite sides we can call it as rectangular columns.  For the rectangular column section the value of eccentricity will be high because the loading will not acts at the center of the section. The minimum number of reinforcing bars required for square columns are considered as 4 as per the IS code standards.

Circular column              

The minimum number of reinforcing bars required for circular columns are considered as 6 as per the IS code standards.

Polygon columns

In the polygon section mostly we will use pentagonal and hexagonal cross sections. The minimum number of reinforcing bars required for the polygon columns are equal to the number of sided considered for the polygon section.

Column Size for 2 Storey and 3 Storey Buildings

Note: Use the below specified dimensions of the column for understanding the concept not applicable for real time projects. Use them only in education purpose.

Column size for 2 storey building

1. For square columns we have to consider 12”X12” (300mmX300mm) dimensions
2. For rectangular columns we have to consider 9”X12” (230mmX300mm) dimensions
3. For circular columns we have to consider 12” Diameter (300mm dimensions)

Column size for 3 storey building

1. For square columns we have to consider 12”X12” (300mmX300mm) dimensions or 14”X14” (380mmX380mm)
2. For rectangular columns we have to consider 12”X14” (300mmX380mm) dimensions
3. For circular columns we have to consider 14” Diameter (380mm dimensions)

Summary of Column Size for 2 Storey and 3 Storey Buildings

The below table shows the complete summary of column sizes we consider for the 2 Storey and 3 Storey Buildings

S. No	Shape of Columns	Two Storey Building	Three Storey Building
1	Square column	12”X12” 300mmX300mm	14”X14” (or) 12”X12” 380mmX380mm (or) 300mmX300mm
2	Rectangular column	9”X12” 230mmX300mm	12”X14” 300mmX380mm
3	Circular column	12” Diameter 300mm Diameter	14” Diameter 380mm Diameter

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Conclusions on column sizes for two storey and three storey building structures

Well now the above explained concepts are related to the dimensions of the columns considered for the two storey buildings and three storey buildings. Here in this article I was taken the shapes related to square, rectangular and circular sections. For the two storey buildings we will take 12”X12” (300mmX300mm) dimensions for square columns, 9”X12” (230mmX300mm) dimensions and 12” diameter (300mm dimensions) for circular cross section columns.

In the same process for the three storey buildings we will take 12”X12” (300mmX300mm) or 14”X14” (380mmX380mm) dimensions for square columns, 12”X14” (300mmX380mm) dimensions and 14” diameter (380mm dimensions) for circular cross section columns.

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