1- Maximum and Minimum Reinforcement Ratio
The minimum reinforcement ratio of 1 % is to be used in tied or spirally reinforced columns. This minimum reinforcement is needed to safeguard against any bending, reduce the effect of shrinkage and creep and enhance the ductility of columns.
2- Minimum Number of Reinforcing Bars
Minimum four bars within rectangular or circular sections; or one bar in each corner of the cross-section for other shapes and a minimum of six bars in spirally reinforced columns should be used.
3- Clear Distance between Reinforcing Bars
For tied or spirally reinforced columns, clear distance between bars should not be less than the larger of 150 times bar diameter or 4 cm.
4- Concrete Protection Cover
The clear concrete cover should not be less than 4 cm for columns not exposed to weather or in contact with the ground. It is essential for protecting the reinforcement from corrosion or fire hazards.
5- Minimum Cross-Sectional Dimensions
For practical considerations, column dimensions can be taken as multiples of 5 cm.
6- Lateral Reinforcement
7- Ties
For longitudinal bars, 32 mm or smaller, lateral ties 10 mm in diameter should be used. In some countries, ties of 8 mm dia are used for column construction.
