Following are the steps to calculate the quantity of steel for RCC slab
1. Prepare a bar bending schedule in order to classify different shapes of bars (bent up bar, straight anchor bar, eos bar, curtail bar, etc) and diameters.
2. List down all the shapes of bars from the drawing.
3. Count the number of bars of each of those shapes.
4. Then calculate the cutting length of each of those bars.
Cutting length of bar = (length of the member – deduction for cover on both sides) + development length.
5. Then calculate the unit weight of each dia bars by the following formula:
W = d^2/162
Where d is the dia in mm and weight (w) in kg.
6. Then calculate the weight of rebar
Weight of rebar= no of bars x cutting length x unit weight
7. Add all the weight to get the total steel quantity.
NOTE – 1. The minimum % of steel as per Indian standards are:
1. Beam (Tension reinforcement):
As = 0.85bd/fy of gross cross-section area.
2. Slab – 0.12% of total area
3. Column – 0.8% of cs area
2. Maximum % steel as per Indian standard are:
Beam – 4 % of cross-section area.
Slab – 4% of cross-section area.
Column — 6% of cross-section area.
3. . Development Length is usually specified in the drawings, but if not then you can calculate it as,
D.L = Depth – 2 times cover
4. Binding wire = 10 grams per kg of reinforcement.
5. No. of stirrups = (length of member – 2 x cover ) / spacing + 1