REINFORCEMENT DETAILING – BEAM, SLAB, COLUMN
The minimum area of tension reinforcement shall be not less than that given by the following-
As / bd =0.85 / fy
As = minimum area of tension reinforcement
b = breadth of beam or the breadth of the web of T-Beam
d = effective depth, and
fy = characteristic strength of reinforcement in N/mm2
The maximum area of tension reinforcement shall not exceed 0.04bD.
Where, D = Total Depth of the section
The maximum area of compression reinforcement shall not exceed 0.04bD.
Side Face Reinforcement
Where the depth of the web in a beam exceed 750mm, side face reinforcement shall be provided along the two faces.
The total area of such reinforcement shall not be less than 0.1 percent of the web area and shall be distributed equally on two faces at a spacing not exceeding 300mm or web thickness whichever is less.
Maximum Spacing of shear reinforcement
The Maximum spacing of shear reinforcement measured along the axis of the member shall not exceed,
- 0.75d for vertical stirrups
- d for inclined stirrups at 45deg
- In no case shall the spacing exceed 300m
Minimum Shear Reinforcement
Maximum shear reinforcement in the form of stirrups shall be provided such that-
Asv / bsv >= 0.4 / 0.87fy
Asv = total cross-sectional area of stirrup legs effective in shear,
sv = stirrup spacing along the length of the member
b = breadth of the beam
fy = characteristic strength of the stirrup reinforcement in N/mm2, which shall not be taken greater than 415 N/mm2.
Distribution of Torsion reinforcement
The transverse reinforcement for torsion shall be rectangular closed stirrups placed perpendicular to the axis of the member. The spacing of the stirrups shall not exceed the least of x1, (x1+y1)/4, and 300mm.
Where, x1 and y1 are respectively the short and long dimensions of stirrup.
When the cross-sectional dimensions of the member exceed 450mm, additional longitudinal bars shall be provided to satisfy the requirements of minimum reinforcement.
All the specification is like beam reinforcement and other detailing is given below.
The mild steel reinforcement in the either direction in slabs shall not be less than 0.15 % of the total cross-sectional area.
However, this value can be reduced to 0.12% when high strength deformed bars or welded wire fabric are used.
The diameter of reinforcing bars shall not exceed 1/8th of the total thickness of the slab.
- The cross-sectional area of longitudinal reinforcement shall not be less than 0.8% nor more than 6% of the gross-sectional area of the column.
- The minimum number of longitudinal bars provided in a column shall be 4 in rectangular columns and 6 in circular columns.
- The bars shall not be less than 12mm in diameter.
- A reinforced concrete column having helical reinforcement shall have at least six bars of the longitudinal reinforcement within the helical reinforcement.
- Spacing of longitudinal bars measured along the periphery of the column shall not exceed 300mm.
- In case of Pedestals, in which the longitudinal reinforcement is not taken in account in strength calculations, nominal longitudinal reinforcement not less than 0.15% of the cross-sectional area shall be provided.
- If the longitudinal bars are not spaced more than 75mm on either side, transverse reinforcement need only to go round corner and alternate bars for the purpose of providing effective lateral supports.
- In the longitudinal bars spaced at a distance of not exceeding 48 times the diameter of the tie is effectively tied in two directions, additional longitudinal bars in between these bars need to be tied in one direction by open ties.
- The diameter of such transverse reinforcement need not, however, exceed 20mm.
Pitch and Diameter of Lateral Ties
The pitch of transverse reinforcement shall not be more than the least of the following-
1. The least lateral dimension of the compression members
2. 16 times the smallest diameter of the longitudinal reinforcement bar to be tied
The diameter of the polygonal links or lateral ties shall not be less than 1/4th of the diameter of the largest longitudinal bar, and in no case less than 16mm.
Pitch-Helical reinforcement shall be of regular formation with the turns of the helix spaced evenly and its ends shall be anchored properly by providing one and a half extra turns of the spiral bar. Where an increased load on the column on the strength of the helical reinforcement is allowed for, the pitch of helical turns shall be not more than 7.5 mm, nor more than 1/6th of the core diameter of the column, nor less than 25 mm, nor less than 3 times the diameter of the steel bar forming the helix.