COLUMN

What is Column?

• We knew that in a framed structure A vertical structural member which can transmit the load from the slab, beam along with its self-weight to the foundation is called column.
• vertical member whose effective length is greater than 3 times Its least lateral dimension carrying compressive loads is called as a column. Columns transfer the loads from the beams or slabs to the footings or foundations. The inclined member carrying compressive loads as In the case of frames and trusses is called as struts. The pedestal is a vertical compression member whose effective length Is less than 3 times Its least lateral dimension. (different types columns)

Why we provide column?

• Columns carry axial loads and therefore are designed for compression.
• Other loads from snow, wind or other horizontal forces can cause bending in the columns.
• We shall build up a small size structure by RR masonry at a certain height but the multi-story building cannot be constructed by RR masonry because the structure can able to transmit the heavy load to the foundation.
• Basically, a column designed to distribute the compressive axial load & additional forces like snow, wind to the foundation eventually & it could be sustained the structure even in the earthquake or any other force majeure.
• Primarily, Columns carry  Axial Loads and therefore are designed for compression. Other loads from snow, wind or other horizontal forces can cause bending in the columns. Columns then need to be designed for Axial Load and Bending

Columns are classified into four types:-

1. Based on Shape
2. Based on a type of reinforcement
3. Based on type of loading
4. Based on slenderness ratio

Column- Based on Shape & Reinforcement

1. Square/Rectangular Column
2. Composite/Encased Column
3. Circular Column
4. Y Type Column
5. T Type Column
6. L Type Column

Square/Rectangular Column

• Most of the building structure was constructed by square or rectangular column. Significantly both are having same components and it is differ based on its architect view.
• These type of column was economically good and easy to do shuttering, placing reinforcement & Concrete.
  
  
  

Composite/Encased Column

• A vertical structural element, with a combination of steel section & concrete it is called as encased or composite column.
• The composite column mostly provided for truss structure to avoid the steel corroded by any type of chemical.
  

Circular Column

• The bending resistant is higher than square/rectangular column.
• It occupies the lesser area.
• Square/rectangular column reinforcement minimum 4 nos of steel will be places in the corner but in a circular column provide more than 4 nos.
• Mostly in building circular column provided for the aesthetic purpose.
• Economically it is little high to compare to square or rectangular column.

they are also provided in sit out areas, auditoriums or fire assembly zones, where you have enough space for them not to hinder any movement of people or look bad with flat surfaces

Y-type Column

• These type of column mostly using for bridges construction.
• The design of bridges to sustain the dead load of the structure & live load of the vehicle motion, the load was eventually distributed to the column.
• These types of columns are generally used in the construction of bridges, flyovers, etc
  

T-type Column

• These type of column having same features like square/Rectangular type column.
• Mostly it was provided along with retaining wall or boundary wall based on design requirement.
• This kind of columns is used depending on design requirements and in the construction of bridges, etc. This has same features of a rectangular or square column
  

L-type Column

• The L type column has used in boundary wall construction and heavy type L column was used in the turning of metro rail or bridges construction.
• They are generally used in the corners of the boundary wall and has same features of a rectangular or square column. These kind of columns are very less used
  

V- Type Column:-

As a name itself, it showcasing the column is in V shape and generally used if the shape of the room is in trapezoidal. As it requires more amount of concrete when compared to the other columns

Y type Column with Arch:

As it is same as Y-type Column but it has curved edges or sides. These are generally provided below the bridges and flyovers where there is a  congestion of building more columns to withstand heavy loads on top

Arch type columns:

These type of columns are used when the room has a shape of an arch. It is adopted where there is a no chance of building square or rectangular or circular type of column. it is rarely used as it possess very difficulty in casting

Hexagon Column:-

Hexagon columns are generally modified columns. It has six sides and it gives good pictorial view generally used in elevation.  It is adopted to give a good look to the column. It is generally provided in open verandahs, Auditoriums, Cinema halls etc

Based on Type of Reinforcement:-

Depending upon the type of reinforcement used, reinforced columns are classified into following types:-

1. Tied Column:

   When the main longitudinal bars of the column are confined within closely spaced lateral ties, it is called as tied column.

2. Spiral Column:

   When the main longitudinal bars of the column are enclosed with in closely spaced and continuously wound spiral reinforcement, it is called as a spiral column.

3. Composite Column:  

   When the longitudinal reinforcement is in the form of structural steel section or pipe with or without longitudinal bars, it is called as a composite column
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1. Base on the type of loading:-

Depending on the type of loading on columns are classified into three types:

Axially loaded Column: –

When the line of action of the compressive force coincides with the center of gravity of the cross-section of the column, it is called axially loaded column. (The total load from top is acted on the centroid of the column.)

Eccentrically loaded column (Uniaxial or Biaxial):

When the line of action of compressive force doesn’t coincide with the center of gravity of the cross-section of the column, it is called as the eccentrically loaded column.

Uniaxial:

We know the X-Axis and Y-axis if load is acted eccentrically either on X or Y axis (anyone) then it is called as Eccentrically loaded column (uniaxial)

Biaxial:

If load is not acting eccentrically on both the axis, that mean load won’t act on either X or Y axis is called Eccentrically loaded column (Biaxial)

Based on Slenderness Ratio:-

Depending upon the Slenderness ratio (ratio of effective length to least lateral dimension of the column), the columns are classified as (most important)It is used extensively for finding out the design load as well as in classifying various columns in short/intermediate/long.

1. Short Column:

   If the ratio effective length of the column to the least lateral dimension is less than 12, the column is called as the short column. A short column fails by crushing (pure compression failure).

2. Long Column:

   If the ratio effective length of the column to the least lateral dimension exceeds 12, it is called as long column. A long column fails by bending or buckling.