Types of Reinforced Concrete Columns
Columns support primarily axial load but usually also some bending moments.The combination of axial load and bending moment defines the characteristic of column and calculation method. A column subjected to large axial force and minor moment is design mainly for axial load and the moment has little effect. A column subjected to significant bending moment is designed for the combined effect. The ACI Code assumes a minimal bending moment in its design procedure, although the column is subjected to compression force only. Compression force may cause lateral bursting because of the low-tension stress resistance. To resist shear, ties or spirals are used as column reinforcement to confine vertical bars. The complexity and many variables make hand calculations tedious which makes the computer-aided design very useful.
Types of Columns
Reinforced concrete columns are categorized into five main types; rectangular tied column, rectangular spiral column, round tied column, round spiral column, and columns of other geometry (Hexagonal, L-shaped, T-Shaped, etc).
shows the rectangular tied and round spiral concrete column. Tied columns have horizontal ties to enclose and hold in place longitudinal bars. Ties are commonly No. 3 or No.4 steel bars. Tie spacing should be calculated with ACI Code.
Spiral columns have reinforced longitudinal bars that are enclosed by continuous steel spiral. The spiral is made up of either large diameter steel wire or steel rod and formed in the shape of helix. The spiral columns are slightly stronger than tied columns.
The columns are also categorized into three types by the applied load types; The column with small eccentricity, the column with large eccentricity (also called eccentric column) and biaxial bending column.shows the different column types depending on applied load.
The column types depending on applied load.
Eccentricity is usually defined by location:
• Interior columns usually have
• Exterior columns usually have large eccentricity
• Corner column usually has biaxial eccentricity.
But eccentricity is not always decided by location of columns. Even interior columns can be subjected by biaxial bending moment under some load conditions shows some examples of eccentric load conditions.