What are Columns?

  • Columns are vertical structural elements that transfer the load from the beams to the foundations. They are classified as short (or stocky) columns or long (or slender) columns.

  • When columns carry only axial load they are called axially loaded columns. However, in actual practice, due to the eccentricity of loads, imperfections in their construction, and so forth, there may be secondary moments in the columns.

  • There may be bending moments due to the rigid frame actions or lateral loads. Such columns with large bending moments are called beam columns. Beam columns may carry uniaxial or even biaxial bending moments.

  • Reinforced concrete columns with rectangular or square shapes are often used because of the simplicity of constructing the formwork. Circular shapes are attractive in open spaces. Square and circular shapes are also preferable in high earthquake zones. L-, + -, and T-shaped columns are also used on rare occasions.

  • Reinforcement in the form of longitudinal bars is often provided to increase the load-carrying capacity of plain concrete columns in the form of closely spaced ties and helical spirals, composite compression members or composite columns as shown in Fig

Different types of columns:

Based on size columns are of following types:
(a) Square-tied column 
(b) Circular spirally reinforced column 
(c) Composite columns