TYPES OF COLUMNS

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Apparently, The featured image above the structural members is meant to be columns. I personally haven’t seen that type of column before. You probably have the same questions like I do but let us analyze this together.

What is the structural integrity of this types of a column?

Can the columns withstand horizontal forces and vertical forces like wind and floods?

Can the columns withstand all the structural failures?

  • The first is that the column might not be strong and tough enough to support the load, due to either its size, shape, or choice of material.
  • The second type of failure is from fatigue or corrosion, caused by instability in the structure’s geometry, design or material properties.
  • The third type of failure is from the use of defective materials. This type of failure is also unpredictable, since the material may have been improperly manufactured or damaged from prior use.
  • The fourth cause of failure is from lack of consideration of unexpected problems. This type of failure can be caused by events such as vandalism, sabotage, or natural disasters. For instance what if vandals hack the blocks which can be easily done because of the joints?

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A column is a vertical structural member intended to transfer a compressive load. For example, a column might transfer loads from a ceiling, floor or roof slab or from a beam, to a floors or foundations.

Columns effective length should be greater than 3 times Its least lateral dimension.

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 can be 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

 

Based on shape   

Columns can be classified according to their cross-sectional shape. Common column shapes include:

  • Rectangular.
  • Square.
  • Circular.
  • Hexagonal
  • Octagonal.
  • Y-shaped column

    Standard gauge railway: Photo credits Nairobi News

In profile, they can be tapered, non-tapered, or ‘barrel’ shaped, their surface can be plain, fluted, twisted, paneled and so on.


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Based on the type of Reinforcement 


Reinforced concrete columns have an embedded steel mesh (known as reinforcement bars ) to provide reinforcement.

The design of reinforcement can be either spiral or tied.

  1. Spiral columns are cylindrical with a continuous helical bar wrapped around the column. This spiral provides support in the transverse direction.
  2. Tied columns have closed lateral ties spaced approximately uniformly across the column. The spacing of the ties is limited in that they must be close enough to prevent failure between them, and far enough apart that they do not interfere with the setting of the concrete.
  3. Composite Columns – 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.

 



Based on type of loading

Here the 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.

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.


Based On Slenderness Ratio 

The slenderness ratio is the effective length of a column in relation to the least radius of gyration of its cross-section. If this ratio is not sufficient then buckling can occur.

Column slenderness is used extensively for finding out the design load as well as in classifying various columns in short/intermediate/long.

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).

The length of the column is less than the critical buckling length. Mechanical failure would typically occur due to compression.

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.

If Length of the column is greater than the critical buckling length. Mechanical failure would typically occur due to buckling.

INTERMEDIATE  COLUMN:
  • In between the long and short columns, and its behaviour is dominated by the strength limit of the material.

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