What Is Column?


 A compression member, i.e., column, is an important element of every reinforced concrete structure. These are used to transfer a load of superstructure to the foundation safely.
 Mainly columns, struts, and pedestals are used as compression members in buildings, bridges, supporting systems of tanks, factories, and many more such structures.
 A column is defined as a vertical compression member who is mainly subjected to the effective length and axial loads of which exceeds three times its least lateral dimension.
 The compression member whose effective length is less than three times its least lateral dimension is called Pedestal
 The compression member who is inclined or horizontal and is subjected to axial loads is called Strut. Struts are used in trusses.
 The function of columns is to transfer the load of the structure vertically downwards to transfer it to a foundation. Apart from the wall performs the following functions also:
(a) It encloses building areas into different compartments and provides privacy.
(b) It provides safety from burglary and insects.
(c) It keeps the building warm in cools in summer and winter.

Also, read: What is CBR Test in Civil
Classification of Columns
A columns are classified based on different criteria such as:


 Shapes of CrossSection
 Material of Construction
 Type of Loading
 Slenderness Ratio
 Type of Lateral Reinforcement

Shapes of CrossSection
 Square
 Rectangular
 Circular
 Pentagonal
 Hexagonal
 Octagonal
 TShape or LShape etc.

Material of Construction

Type of Loading
 Axially Loaded Column
 Eccentrically Loaded Column

Slenderness Ratio
 Long Column
 Short Column
 Intermediate Column

Long Column


 When this ratio of effective length to the least radius of gyration is greater than 45, then it is called a long column.
 A long column is subjected to a bending moment in addition to direct compressive stress.
 The loadcarrying capacity of a long column is less than a short column.
 The loadcarrying capacity of a long column depends upon slenderness ratio (slenderness ratio increases then the capacity of the column decreases)
 When the length of a column is more as compared to its c/s dimension, it is called a long column.
 Le/r min > 50
 Where,
 Le. = Effective Length of Column
 r min = Minimum radius of gyration

Also, read: Difference Between Lap Length and Development Length
Short Column


 When this ratio of effective length to the least lateral dimensions of this column is less than 12, then it is knowns a short column.

(or)


 When this ratio of effective length to the least radius of gyration is less than 45, then it is called a short column
 When the length of the column is less as compared to its c/s dimension, it is called the Short column.
 Short Column
 Le/r main < 50

Or,



 Le/d < 15
 Crushing Load: The load at which a short column fails by crushing is called a crushing load.


Intermediate Column


 Column is Intermediate

 30d > L > 4d
 and
 100 > Le / r min > 30or Critical slenderness ratio.

 Column is Intermediate

Also, read: What Is Guniting, Set Guniting Systems , Advantage, Disadvantage
Difference Between Short Column and Long Column
Sr.No.  Long Column  Short Column 

1  This column is considered to be long if the ratio of effective length of column to its least lateral dimension is greater than 12.  This column is considered to be short if the ratio of effective length to its least lateral dimension is less than or equal to 12. 
2  The column, whose lateral dimension is very small when compared to its length (or height), is called as long column.  The column, whose lateral dimension is very large when compared to its length (or height), is called a short column. 
3  It is generally fails by buckling.  It generally fails by crushing. 
4  The slenderness ratio is greater than 45.  The slenderness ratio is less than 45. 
5  As the height of column increases the load carrying capacity is less.  As the height of the column decreases the loadcarrying capacity is more. 
6  The Radius of gyration is less.  The radius of gyration is more. 
7  Load carrying capacity is less.  Loadcarrying capacity is more. 
8  Long column is subjected to buckling stress  The short column is subjected to compressive stress. 
9  Long and slender columns buckle easily.  The buckling tendency is very low. 
10  The ratio of effective length of a long column to its least radius of gyration is greater than 40.  The ratio of the effective length of a short column to its least radius of gyration is less than or equal to 40. 
11  The failure of the short column is by crushing.  The column generally fails in buckling. 
Also, read: What Is Lap Length  Lap Length of Column  Lap Length of Slab  Lap Length of Beam


Type of Lateral Reinforcement
 A column with Lateral Ties
 A column with Helical Ties

Also, read: Difference Between Footing and Foundation  What is Footing and Foundation
Failure Mode of Column


 A column can fail in one of three condition
 Compression failure of concrete or steel reinforcement
 Buckling
 Combination of compression and buckling failure
 Compression failure is likely to occur with columns that are short and stocky.
 Buckling is probable with a column which is long and slender

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