Reinforcement in a Column

Concrete is strong in compression. Thus, a column can be made up of plain concrete but it is always advisable to use R.С.С. columns instead of plain concrete columns because of following reasons:

1. A plain concrete column requires very large area as compared to R.C.C. columns. We have seen earlier that steel can take load m-times that of concrete of the same area. For a particular load, the section of an R.C.C. column will be much thinner than that of plain concrete. Thus by using R.С.С. columns a lot of space can be saved as the size of the column will be less.
2. A minimum area of steel is always provided in the column whether it is required for carrying load or not. It is done to resist tensile stresses which may be caused due to eccentricity of loads. (It is practically impossible to have a perfectly axially loaded structure).

There are two types of reinforcements provided in a R.C.C. column.

1. Longitudinal reinforcement.
2. Transverse reinforcement.

Longitudinal Reinforcement

The longitudinal reinforcement consist of steel bars placed longitudinally in a column. It is also called as main steel. The functions of longitudinal reinforcement are as follows:

1. To share the compressive loads along with concrete, thus reducing the overall size of the column and leaving more usable area.
2. To resist tensile stresses developed due to any moment or accidental eccentricity.
3. To impart ductility to the column.
4. To reduce the effect of creep and shrinkage due to continuous constant loading applied for a long time.

Transverse Reinforcement

The transverse reinforcement is provided along the lateral direction of the column in the form of ties spirals enclosing the main steel. The function of transverse steel are as following:

1. To hold the longitudinal bars in position.
2. To prevent buckling of the main longitudinal bars.
3. To resist diagonal tension caused due to transverse shear developed because of any moment or load.
4. To impart ductility to the column.
5. To prevent longitudinal splitting or bulging out of concrete by confining it in the core.