COLUMNS IS 456 2000

S.NoDescriptionReference

1Eff. Length of which exceed 3 times the least lateral dimensions is called Column otherwise it is called pedestalIS 456 - 2000Clause 25.1.1

2Slenderness ratios Lex/D and Ley/b are less than 12 is called Short Column, otherwise it is considered as Slender Column.IS 456 - 2000Clause 25.1.2

3Unsupported length between end restraints shall not exceed 60 times the least lateral dimension of a columnIS 456 - 2000Clause 25.3.1

4Reinforcement - Longitudinal Reinforcement Min. Rein. = 0.8% of gross c/s area of concrete Max. Rein. = 4% of gross c/s area of concrete Min. number of bars = 4 for Rectangular column Min. number of bars = 6 for Circular column Min. Diameter of Longitudinal steel = 12mm Spacing of bars should not exceed 300mm Spacing of bars should not exceed 300mm For Pedestal = 0.15% of c/s area of pedestalIS 456 - 2000Clause 26.5.3.1

5Reinforcement - Transverse ReinforcementLong. Bar spaced at dist. less than 75mm, transverse rein. need only to go round corner and alternate bars for providing eff. lateral support. See Fig. 1IS 456 - 2000Clause 26.5.3.2

6Min. Cover = 40mm or bar dia. (whichever is greater)IS 456 - 2000Clause 26.4.2.1

7Minimum Eccentricity, e = L/500 + D/30 < 20mmIS 456 - 2000Clause 25.4

8Reinforcement - Transverse ReinforcementLong. Bar spaced at a distance less than 48 times the dia., of tie are effectively ties in two directions, additional long., bars in between these bars need to be tied in one direction by open ties. See Fig.2IS 456 - 2000Clause 26.5.3.2

9Pitch and diameter of lateral tiesDiameter - Dia., of lateral ties shall be not less than 1/4 of dia of largest long., bar and in no case less than 5mm [ not less than /4 or 6mm) whichever is greater]

Pitch - Pitch of lateral ties shall not be more than the least following: - Least lateral dimension of the compression member - 16 times the smallest dia., of long. Bar- 300mm(Less than b or 16 or 300 mm )

IS 456 - 2000Clause 26.5.3.2 c

Ductile Details of Reinforced Concrete Structures Subjected to Seismic ForcesAs per IS 13920 1993

1General

Frame members which have a factored axial stress in excess of 0.1fck under the effect earthquake forces. Min. dimension of the member shall not be less than 200mm. In frames, beams with centre to centre span exceeding 5m or columns of unsupported length exceeding 4m, the shortest dimension of the column shall not be less than 300mm. The ration of the shortest cross sectional dimension to the perpendicular dimension shall preferably not be less than 0.4IS 13920 - 1993Clause 7.1

2Longitudinal Reinforcement

Lap splice shall be provided in the center of the member Hoops shall be provided over the entire splice length at spacing not exceeding 150mm c/c. Not more than 50% of the bars shall be spliced at one section.IS 13920 - 1993Clause 7.2

3Transverse Reinforcement

For circular column spiral or circular hoops are provided. In Rec. column rectangular hoops may be used. A rectangular hoop is a closed stirrup, having a 135 hook with a 10 diameter extension (but not < 75 mm) at each end, which is embedded in the confined core. The parallel legs of rectangular hoop shall be spaced not more than 300mm center to centre. If the length of the hoop exceeds 300mm, a crosstie shall be provided. The hooks shall engage peripheral longitudinal bars.

IS 13920 - 1993Clause 7.3

4Special Confining Reinforcement

Special confining reinforcement shall be provided over a length lo from each joint face, towards mid span and on either side of any section. The length lo shall not be less than i. Larger lateral dimension of the member at the section where yielding occurii. 1/6 of clear span of the memberiii. 450mm Column terminates into footing; special confining reinforcement shall extend at least 300mm into the footing. The spacing of hoops as special confining reinforcement shall not exceed of min. member dimension but need not be less than 75mm nor more than 100mm

IS 13920 - 1993Clause 7.4