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:
- It encloses building areas into different compartments and provides privacy.
- It provides safety from burglary and insects.
- It keeps the building warm in cools in summer and winter.
Classification of Columns
A columns are classified based on different criteria such as:
- Shapes of Cross-Section
- Material of Construction
- Types of Loading
- Slenderness Ratio
- Â Types of Lateral Reinforcement
Shapes of Cross-Section
- SquareÂ
- Rectangular
- Circular
- Pentagonal
- Hexagonal
- Octagonal
- T-Shape or L-Shape etc.
Material of Construction
- Timber Column
- Masonry Column
- R.C.C Column
- Steel Column
- Composite Column
Types of Loading
- Axially Loaded Column
- Eccentrically Loaded Column
Slenderness Ratio
- Long Column
- Short Column
- Intermediate Column
What Is Short Column?Â
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
A short column is the one whose ratio of effective length to its least lateral dimension is less than or equal to 12. Then it is termed as a short column.
 lef / b ≤ 12
lef = effective length
b = least lateral dimension of column
What Is Intermediate Column? | Intermediate Column
Column is Intermediate
30d > L > 4d
and
100 > Le / r min > 30or Critical slenderness ratio.
What Is Long Column?
A long or slender column is the one whose ratio of effective length to its least lateral dimension is not less than 12. Then it is termed as a long column.
 lef / b ≤ 12
lef = effective length
b = least lateral dimension of 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 load-carrying capacity of a long column is less than a short column.
The load-carrying capacity of a long column depends upon slenderness ratio (slenderness ratio increases then the capacity of the column decreases).
Difference Between Short Column and Long Column
| Sr.No. | Long Column | Short Column |
| 1 | Long column is considered to be long if the ratio of effective length of column to its least lateral dimension is greater than 12. | Short 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 | Long column is weaker than a short column and generally, it is not preferred. | The short column is stronger than a long column and it is highly preferable. |
| 3 | Â Long column, whose lateral dimension is very small when compared to its length (or height), is called as long column. | Short column, whose lateral dimension is very large when compared to its length (or height), is called a short column. |
| 4 | It is generally fails by buckling. | It generally fails by crushing. |
| 5 | The slenderness ratio is greater than 45. | The slenderness ratio is less than 45. |
| 6 | As the height of column increases the load carrying capacity is less. | As the height of the column decreases the load-carrying capacity is more. |
| 7 | Long Column Radius of gyration is less. | Short column radius of gyration is more. |
| 8 | Load carrying capacity is less. | Load-carrying capacity is more. |
| 9 | Long column is subjected to buckling stress | The short column is subjected to compressive stress. |
| 10 | Long and slender columns buckle easily. | The buckling tendency is very low. |
| 11 | 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. |
| 12 | The failure of the short column is by crushing. | The column generally fails in buckling. |
Types of Lateral ReinforcementÂ
- A column with Lateral Ties.
- A column with Helical Ties.
Failure Mode of Column
- A column can fail in one of three conditions.
- 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.
FAQ
What Is a Column in Structural Engineering?
A column is a vertical compression member that transfers the load from the superstructure to the foundation. It is primarily used to support and distribute loads vertically downward.
What Are the Different Types of Compression Members?
Compression members include columns, struts, and pedestals. Columns are vertical, struts are inclined or horizontal, and pedestals have a short height compared to their cross-sectional dimensions.
How Is a Column Classified Based on Its Shape?
Columns can have various cross-sectional shapes, including square, rectangular, circular, pentagonal, hexagonal, octagonal, and T- or L-shaped.
What Materials Are Commonly Used for Constructing Columns?
Columns can be constructed from timber, masonry, reinforced concrete (R.C.C), steel, or composite materials.
What Is the Difference Between a Short Column and a Long Column?
A short column has a ratio of its effective length to the least lateral dimension of 12 or less, while a long column has this ratio greater than 12. Short columns typically fail by crushing, while long columns are more likely to fail by buckling.
What Is an Intermediate Column?
An intermediate column has a ratio of effective length to its least lateral dimension between the limits of short and long columns. It typically falls into a range where specific slenderness ratios apply.
How Does the Slenderness Ratio Affect a Column’s Performance?
The slenderness ratio influences the column’s load-carrying capacity and its tendency to buckle. A higher slenderness ratio generally results in reduced load capacity and increased susceptibility to buckling.
What Are Lateral Reinforcements in Columns, and Why Are They Important?
Lateral reinforcements include lateral ties and helical ties. They are crucial for enhancing the stability and load-carrying capacity of columns, preventing buckling, and ensuring structural integrity.
What Are the Common Failure Modes of Columns?
Columns can fail due to compression failure of the concrete or steel reinforcement, buckling, or a combination of both. Short columns typically experience compression failure, while long columns are prone to buckling.
How Is the Load-Carrying Capacity of a Column Determined?
The load-carrying capacity depends on factors like the column’s material, cross-sectional shape, slenderness ratio, and the type of loading. The capacity is generally higher for short columns compared to long columns.
