How To Calculate Steel Quantity From Drawing

How to Calculate Steel Quantity From Drawing?

Data requires for steel quantity calculation

1) Plan of Section or Element. (Slab, Beam, Column & Foundation)

2) Section and Elevation Details.

3) All dimensions must be clear and co-related.

General Guidelines To Be Followed In Preparing BBS

• The bars are required to be grouped together for each of the structural units, For e.g. beam, etc.
• In a building structure, the Listing of bars should be done floor to floor.
• For cutting and bending operations, schedules should be provided separately in the form of A4 sheets and should not be a part of the detailed reinforcement drawings.
• The form of the bar, fabric schedule, and the shapes of the bar used should be according to BS 8666.
• It is always preferable that bars should be listed in numerical order in the schedule for better understanding.
• The bar mark reference on the label which is attached to a bundle of bars refers separately and uniquely to a specific group of defined length, size, shape, and type used on the job.
• This is very crucial as a bar mark reference can then state a class of bar characteristics. Similarly, it is also helpful in the case of steel fixers and laborers can keep track of the type and number of bars needed to complete a specific work.

Steel Quantity Calculation

Let, we take one example of a slab for steel quantity calculation.

Following Steel Quantity, we have to calculate from the drawing.

• Cement Concrete for Slab.
• Centering and Shuttering for Slab.
• Weight of 12mm dia. Bars.
• Weight of 8mm dia. Bars.
• Prepare Bar Bending Schedule.

(Note:  Weight of Steel bars 12mm – @ 0.9 kg / m

                                              8 mm – @ 0.4 kg/m,

Slab Steel Quantity Calculation Estimation Sheet

Sr. No.	Item Description	No.	Length (m)	Width	Height	Quantity
1	Cement Concrete for Slab (1:1.5:3):
	L = 4 + 0.23 + 0.23 = 4.46 m	1	4.46	3.46	0.12	1.85 cu m
	B = 3 + 0.23 + 0.23 = 3.46

(See drawing in to in dimension (without the wall) of the slab is given 3 m x 4 m. For calculating the Quantity of slab concrete we have to calculate the dimension of the slab.)

2	Centering & Shuttering for Slab:
	Bottom	1	4.00	3.00	–	12.00	cu m
	Sides	2	4.46	–	0.15	1.34	cu m
	( Take 30mm Extra Above Slab Thickness)	2	3.46	–	0.15	1.04	cu m
					Total	14.38	cu m

(Formwork Quantity is calculated in a square meter. There is one bottom portion and 4 sides shuttering. For the bottom, we have a dimension of slab 3m x 4m. For Side formwork, there are 2 different dimensions, 2 with 4 m wide and 2 with 3 m sides. For the total length we have to add the wall width of both sides to get the total length.)

Read More: Estimation of a Building with Plan

Steel Quantity Formula

3	12 mm dia main Steel bars @ 150 mm c/c Alternate bent up.
	L = 3 + 0.23 + 0.23 + (2 x 9 x 0.012) – (2 x 0.05)
	L = 3.58 (Straight Length) (For finding out nos. of the bar we have to calculate the straight length of the main bar without adding extra length due to bent up)
	Span = 4 + 0.23 + 0.23 – (2 x 0.05)           = 4.36 m
	No. of Bars = (4.36/0.15) + 1                      = 30 nos.
	Extra Length of Bent up:

	Extra Length = 0.45 X
	X = 0.12(Slab Thickness) – 2 x 0.02 (Top & Bottom Cover) – 0.012/2(Harf dia top) – 0.012/2( Half dia bottom)
	X = 0.12- 2 x 0.02 – 0.012/2 – 0.012/2 = 0.068 m
	L = 3.58 + 0.45X L = 3.58 + 0.45 x 0.068 3.61	30	3.61	@	0.90	97.47	kg

(In case of bent bars are provided on both sides, we have to add 0.45 X twice in length)

4	8 mm dia. Distribution steel @ 180 mm  c/c
	Bars at Bottom:
	Hook Length = 9d                          = 9 x 0.008                          = 0.072 < 0.075 ( Mini. Hook length = 0.075)
	L = 4 + 0.23 + 0.23 + 2 x 0.075(Both side hook(9d)
	L = 4.51 m
	Width of Slab = 3 + 0.23 + 0.23 – 2 x 0.05 (Both Side Cover) = 3.36 m
	No. of Bars = (3.36 / 0.18) + 1 = 20 nos.
	Bars at Top:
	Width of Slab at one end for bent up at the Top
	L= 0.23 +  0.45 – 0.068 – 0.05(cover)
	(When the bent-up bar is bent to the top at the end of the bar, there is also distribution steel is provided. we have to add these bars to the total distribution steel bar nos.)
	L = 0.562 m
	Nos. of Bars at one End: = (0.562/0.18) + 1 = 5 nos.
	Nos. of bars on both sides  = 2 x 5 = 10
	Total Bars = 20 + 10 + 30	30	4.51	@	0.40	54.12	kg

BBS for Slab

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