Classification of Columns

  • A Column or strut is defined as a compression member whose effective length exceeds three times the least lateral dimension.

Read in details: What are Columns?

  • A structural element that is predominantly subjected to axial compressive forces is termed a compression member.

  • When a compression member is vertical, it is called a column, and when it is horizontal or inclined, it is called a strut.

Classification of Columns

The Classification of columns can be done on following Basis:

Classification of Columns based on Cross Section

1.Rectangular Columns
2.Square Columns
3.Circular Columns
4.Hexagonal Columns
5.T, L, or + shapes Columns

Classification of Columns based on Type of Reinforcement

1.Tied columns
    Columns reinforced with longitudinal reinforcement and lateral (transverse) ties. Tied columns are applicable to all cross-sectional Shapes.

2.Spiral columns:
    Columns with longitudinal reinforcement tied by continuous spiral reinforcement. Spiral reinforcement is used mainly in columns Of circular cross-section, though they can have hexagonal, octagonal, or even square shapes.

3.Composite columns
     Columns reinforced longitudinally with structural steel sections, such as hollow tubes and I-sections, with or without additional longitudinal reinforcement or transverse reinforcement.

Classification of Columns based on Types of Loading

Classification of columns
Cross section of column with different types of loading (a) Concentric axial loading (b) Loading with one axis eccentricity (c) Loading with biaxial eccentricities

1.Columns with concentrically applied loads: 
   Such columns with zero bending moments are rare. In multi-storey frames, interior columns will be subjected to axial compression and shear, under gravity loads.

2.Columns with uniaxial eccentricity—ex = 0, ey ≠ 0 or ex ≠ 0, ey = 0: 
    Edge columns such as B and D in Fig. 13.3 are subjected to uniaxial bending moments.

3.Columns with biaxial eccentricity—ex ≠ 0 and ey ≠ 0: Corner columns like C in multi-storey buildings are subjected to biaxial bending moments in addition to the compressive force. When subjected to lateral loads, most of the columns will be subjected to uniaxial or biaxial bending moments.

Classification of Columns based on Slenderness Ratio

What is Slenderness Ratio?
The Slenderness ratio of a member is defined as the ratio of the effective length and the radius of gyration of the section.

Columns, struts, beams, and ties are often slender members. 

Based on the slenderness factor, columns can be classified as follows:

1.Short columns: These types of columns generally fail after reaching the ultimate load carrying capacity of columns.

2.Slender columns: These types of columns generally fail suddenly at relatively low compressive loads due to buckling.

Read also: What are Columns?