What Is Column?
Column is a vertical member which transfers loads of a structure from beam and slab to the foundation. The effective depth of a column exceeds three times the lateral dimension. Generally, columns carry axial loads in compression. Columns are very important components of a structure. Failure of columns results in the collapse of structure.
Types Of Columns:
There are different types of columns used in structures. Columns can be classified depending upon several conditions, which are
1. Based on the shape.
2. Based on the type of reinforcement.
3. Based on the types of loading.
4. Based on the slenderness ratio.
5. Based on materials.
Based On Shape:
Square Or Rectangular Column:
Square or rectangular columns are mostly used in building construction. These types of columns are economically good and easy to construct because of it’s easy shuttering and reinforcement placement.
Circular columns are mostly used in piling and elevation of the buildings for aesthetic purposes. In circular column, more than 4 steel bars are used as reinforcement and its bending resistance is usually higher than square or rectangular column. Other than buildings, circular columns are also used as bridge pillars due to good deflection resistance.
L Type Column:
L type columns are used in boundary wall construction and in the turning of metro rail or in flyover construction.
T Type Column:
T type column has same feature as square/ rectangular column and mostly used in bridge and retaining wall construction.
Y Type Column:
These types of columns are mostly used in bridge and flyover construction.
Some other types:
Based On The Type Of Reinforcement:
These columns have closed lateral ties spaced approximately and uniformly across the column. The spacing of the ties is limited in that they must be close enough to prevent barrelling failure between them, and far enough apart that they do not interfere with the setting of the concrete. If ties are spaced too far apart, the column will experience shear failure and barrelling in between ties.
When circular columns are reinforced with closely and uniformly spaced spiral reinforcement, they are known as spiral columns. The spiral acts to provide support in the transverse direction and prevent the column from barrelling. Spirally reinforced columns generally consist of 6 bars as longitudinal reinforcement.
These columns consist of structural steel or cast iron column enclosed with concrete, reinforced with longitudinal as well as spiral reinforcement. Composite columns are mostly used in truss structures to avoid the corrosion of steel.
Based On The Type Of Loading:
Axially Loaded Column:
When the resultant of the load coincides with the centroid of the cross-section of a column, it is called axially loaded or concentrically loaded column. These types of columns rarely used in construction.
Eccentrically Loaded Column:
When the resultant of the load does not coincide with the centroid of the cross-section of a column, it is called axially loaded or eccentrically loaded column.
1. Uniaxially Eccentrically Loaded Column:
When the eccentric load acts on either X-axis or Y axis is called uniaxially eccentrically loaded column.
2. Biaxially Eccentrically loaded column:
When the eccentric load does not act on either X-axis or Y-axis it is called biaxially eccentrically loaded column.
Based On Slenderness Ratio:
When the ratio of the effective length of the column to its least lateral dimension is less than 12, it is called short column. In short column mechanical failure mainly occur due to shearing.
When the ratio of the effective length of the column to its least lateral dimension exceeds 12 the column is considered as long column. Such columns are liable to fail due to buckling. Long columns are weaker compared to short columns of same cross-sectional area and not generally preferred.
Based On Materials Used:
1. Reinforced concrete column.
2. Steel column.
3. Timber column.
4. Stone Column.
5. Brick column.
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