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Columns are defined as long slender member load axially in compression and having lateral dimensions very small as compared to their lengths.
A vertical compression member is called a column. If load passes through the longitudinal axis coinciding with the CG of the column, it is called the axially loaded column, otherwise eccentrically loaded column.
Columns are the building structures connected to different footings to transfer the load of the building to the footings of the buildings.
1. Types of Columns
There are different types of columns, which are listed below depending on various factors:
a. Based on Loading
Types of Columns based on loading are as follows:
a. Axially Loaded Columns
When the compressive vertical loads lie along the centroidal axis of the column, it is known as an axially loaded column. This type of column without bending is not available in the real world so much.
b. Eccentrically Loaded Column: Uniaxial
When the loads on the column are lying at a distance ‘e’ from the centroid of the column cross-section, the column is known as an eccentrically loaded column. In a uniaxial eccentrically loaded column this distance ‘e’ could be along the x-axis or y-axis. The eccentric loads result in moments along the x-axis or y-axis at the same time.
c. Eccentrically Loaded Column: Biaxial
In this type of column, loads are loaded at any point of cross-section but not on the axis. The eccentric loads result in moments about both the x- and y-axes at the same time.
b. Based On Column Ties
Types of Columns based on column ties are as follows:
a. Tied Column
The longitudinal bars are bound together with smaller bars are the tied column. These smaller bars are placed at uniform gaps up the column. Steel ties in columns enclose the main longitudinal bars.
Over 95 % of all columns in structure in non-seismic regions are bounded columns.
b. Spiral Column
Spiral columns include spirals to support the main longitudinal reinforcement. Spiral is spring-type reinforcement used in the buildings. The main bars are kept in a circle and ties are removed by spirals.
Spiral columns are utilized when high strength and/or high ductility are needed. Because the spiral acts to withstand the lateral expansion of the column bars under high axial loads. The main bars are kept in a circle and ties are removed by spirals. Spiral columns are utilized more highly in seismic regions.
c. Based On Slenderness
Types of Columns based on slenderness are as follows:
a. Short Compression Block or Pedestals
A pedestal is a compression member containing a height lower than three times its least lateral dimension. Pedestals require not to be reinforced and may be prepared with plain concrete.
b. Short Reinforced Column
The slenderness ratio is the ratio of effective length to the least lateral dimension. It is less than 12 in the short reinforced column. Short columns collapse because of the crushing or yielding of the steel bars. The loads that a short column may hold are based on the dimension of the cross-section and the strength of materials. The short columns provide low flexibility.
c. Long Reinforced Column
The slenderness ratio is more than 12 long columns and this type of column is also termed the slender column. As the slenderness raise, bending deformation raises. The long column collapse due to the buckling effect which decreases load-bearing capacity.
d. Based On the Shape of the Cross Section
Types of Columns based on the shape of the cross-section are as follows:
Column segments can be rectangular, round, square, octagonal, or hexagonal as per need.
Tied columns can be square and rectangular while spiral columns are made of circular shapes. Circular columns are utilized when higher elevation is required like in piles, and bridge pillars. Circular columns give a smooth and aesthetic finish. On the other hand, rectangular columns are available in residential and official buildings. They are easy and less costly to mold.
This type of column isn’t very popular. The L-shaped column can be utilized as a corner column in a framed structure. This design of the column can be the best replacement to withstand both axial compression and biaxial bending of corners.
In the trapezoidal structure, this type of column can be utilized. V-shaped columns require more materials relatively.
T-shaped columns are utilized in bridge pillars depending on design criteria.
e. Based on Construction Materials
Types of Columns based on construction material are as follows:
a. Reinforced Concrete Column
Reinforced concrete columns are the most widely used columns for framed structures. The reinforced concrete column is made of concrete as a matrix. The steel frame is attached to the concrete.
Concrete support the compressive load and reinforcement withstand the tensile load. The reinforcing materials can be prepared of steel, polymers, or other composite materials.
For a strong, ductile, and durable work the reinforcement requires to have features like thermal compatibility, high resistance to tensile stress, good bond to concrete, anti-corrosive, etc.
b. Composite Column
Composite columns are prepared to utilize a different combination of structural steel and concrete. The interactive and integral behavior of concrete and the structural steel elements constructed the composite column into a very stiff, more ductile, cost-effective, and so a structurally systematic member of building and bridge construction. The composite type of column has the best capacity to withstand fire and corrosion resistance.
c. Steel, Timber, Brick Column
Steel columns are made of steel entirely. Steel, Timber, and Brick columns are utilized in aircraft constructing warehouses, indoor shipyards, etc. Timber columns are prepared of wood timber. They give an aesthetic appearance giving a feeling of space and openness.
Timber columns are prepared for housebuilders, reception areas, and refurbishment features. Brick columns are available in masonry structures. They can be reinforced with concrete to expand strength or can be unreinforced.
The brick columns can be round-shaped, rectangle, square, or elliptical in cross-section.
f. Based on Frame Bracing
Types of Columns based on frame bracing are as follows:
a. Braced Column
Columns can be components of a frame that is braced or unbraced sideways. Lateral stability to a structure as a whole is given by bracing. Bracing can be done by utilizing shear walls or bracings in the building frame. In braced frames, comparative transverse movement of the upper and lower ends of a column is saved. Braced columns safe gravity loads and shear walls safe lateral loads and wind loads.
b. Unbraced Column
Unbraced columns can withstand both gravity load and lateral load. As a result, the load capacity of the column decreases.
g. Other Types of Columns
a. Prestressed Concrete Column
Prestressed columns can be used as an extension of the reinforced concrete columns when bending moments due to wind and earthwork forces, eccentric loads, or frame action are utilized to columns. Prestressing transforms a cracked section into a non-cracked one and withstands notable bending. This type can be available useful when the column is a high slender column and precast column.
b. Greek And Roman Columns
Greek and Roman architecture made use of four major styles of columns for their buildings and temples.
These four types of columns were Doric, Ionic, Corinthian, and Tuscan. These columns look straight and uniform from a distance. But up close, they might actually tilt a bit, or lean left or right.
2. Dimensions of Columns in Different Countries
|Country||Column Size (MM X MM)|
|USA||225 x 225|
|India||229 x 305|
|UK||254 x 254|
|Philippines||225 x 300|
|Nepal||305 x 305|
|Japan||400 x 280|
3. Uses of Columns
Here are the following uses of columns:
✔ It is used to support arches and beams.
✔ It is used to increase the aesthetic beauty of buildings.
✔ It is used to transfer the load to the foundation.
4. Advantages of Columns
✔ It adds visual appeal or polish.
✔ It transfers the superstructure load to the ground.
✔ It is durable.
✔ Number of floors can be constructed.
5. Disadvantages of Columns
The disadvantages of columns are as follows:
✔ Cracks are formed.
✔ Excavation of soil is needed which will increase construction cost.
✔ Columns get weaker with time.
✔ It can’t resist weather agencies and fire.
|Read Also: Lap Length|
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