The points to be considered for reinforcement estimate
Computation of steel reinforcement quantity is necessary for working out cost of RCC structure together with other building materials with adherence to construction drawing. Precise quantities of the concrete and brickwork are computed from the layout drawings.
If working drawings and schedules for the reinforcement are unavailable it is required to formulate an estimate concerning the projected quantities. The quantities are generally defined according to the needs of the Standard method of measurement of building works.
Now as soon as you estimate the bar size, length and quantity, paste the data in a spreadsheet. Multiply every sort of bar by it's diameter and length to obtain the volume. And perform this for each entry in your excel column. Multiply the total volume by density of steel and you can obtain the weight of rebar too.
If you want to make perfect estimates for reinforcement, consider the following points :-
1. For beam hook= (beam depth - both side covers)/2.
As for instance, if the depth of the beam is 450mm, then hook will be (450-50)/2=200, here cover for beam is considered as 25 mm
2. For stirrups the hook=4d in accordance with codes but as per site conditions it should be 50 mm per hook at the time of carrying out bar bending schedule.
3. For slab the rod, the crank length is l/5.
4. For beam, the bottom extra is at l/6.
5. For slab the top extra expands upto l/3.
6. For beam the top extra bar expands upto l/3.
7. The column capitals expand upto l/4.
8. Where l denotes actual length of the beam. It is considered as center to center of the beam.
9. The crank length is 1.41d, where d denotes depth of slab or beam – two side cover.