REQUIREMENTS GOVERNING REINFORCEMENT (COLUMNS-LONGITUDIONAL REINFORCEMENT)

Code of practice for plain and reinforced concrete,the Indian standard was adopted by the Indian Standard institution on 3-10-1978 after the draft finalised by the cement and concrete sectional Committee had been approved by the civil engineering division council. The present revision was taken up with a view to keeping abreast with the rapid development in the field of Concrete technology and also to bring it in further clarifications and required modifications in the light of experience gained while applying the provisions of the earlier versions of the code to practical approach and situation. An attempt has too been made to unify the approach for the design of reinforced concrete and prestressed concrete structures and the code of practice for prestressed concrete (IS :1343 ) is being revised simultaneously with this in view .Further it is mentioned in the case of Columns that the longitudinal reinforcement ,the cross sectional area of longitudinal reinforcement shall be not less than 0.8 percent nor more than 6 percent of the gross cross sectional area of the column.(2) In any column that has a larger  cross sectional area than that required to support the load , the minimum percentage of steel shall be based upon the area of concrete required to resist the direct stress and not upon the actual area .(3) The minimum number of longitudinal bars provided in a column shall be four in the rectangular Columns and six in the circular Columns.(4) The bars shall not be less than 12 mm in diameter.(5) A reinforced concrete Column having helical reinforcement shall have atleast six bars of longitudinal reinforcement with in the helical reinforcement.(6) In a helically reinforced Column the longitudinal bars shall be in contact with the helical reinforcement and equidistant around its inner circumfrence . Spacing of longitudinal bars measured along the periphery of the Column shall not exceed 300 mm.(8) In case of pedestals in which the longitudinal reinforcement is not taken into account in strength calculations, nominal longitudinal reinforcement not less than 0.15 percent of the cross sectional area shall be provided. NOTE :-- Pedestal is a compression member, the effective length of which does not exceed three times the least lateral dimensions.