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Bar bending schedule (BBS) of a Chajja (sunshade). Type-1 / Calculating the cutting length & weight of reinforcement in a window projection (sunshade).

 Let us make BBS of the Chajja or RCC sunshade as shown below.




Given data:

Length of sunshade = 1500mm.

Width of sunshade = 900mm.

Sunshade thickness (front) = 75mm.

Lintel beam width = 230mm.

Lintel beam depth = 350nmm.

Main bar = 10∅ @ 150c/c.

Distribution bar = 8∅ @ 150 c/c.

Sunshade clear cover =20mm.

Lintel beam cover = 25mm.


Calculation:

A. Cutting length:

1. Cutting length of main bar

= [{sunshade thickness - (2nos. × cover)} + (sunshade width - cover) + {2nos.×  (lintel width - cover)} + 100mm. + (100mm. - lintel cover) - (3nos. × 90° bend.) ]

=  [{75mm. - (2nos. × 20mm.)} + (900mm. - 20mm.) + {2nos.×  (230mm. - 20mm.)} +100mm.+ ( 100mm.- 25mm.) - (3nos. × 2 × 10mm.) ]

=  [{75mm. - (40mm.)} + (880mm.) + {2nos.×  (210mm.)} +100mm.+ ( 75mm.) - (60mm.) ]

= [ 35mm. + 880mm. + 420mm. + 115mm.]

= 1450mm.

= 1.45m.


2. Cutting length of distribution bar

= [ sunshade length - (2nos.× sunshade cover)] 

= [ 1500mm. - ( 2nos. × 20mm.)]

= 1460mm.

= 1.46m.


B. No. of bars:

1. No of main bars

= [{sunshade length - (2nos. × cover)} ÷ c/c distance ] +1

= [{1500mm. - (2nos. × 20mm.)} ÷ 150mm. ] +1

= [ {1460mm.}  ÷ 150mm. ] +1

= 9.73 +1

= 10.73

By rounding off = 11 nos.


2.  No of distribution bars

= [{sunshade width - cover - main bar dia} ÷ c/c distance ] +1

= [{900mm. - 20mm. - 10mm} ÷ 150mm. ] +1

= [ {870mm.}  ÷ 150mm. ] +1

= 5.8 +1

= 6.8

By rounding off = 7 nos.


If you want to know how to prepare BBS of lintel beam, Go through the article👇

💁 ° How to calculate the cutting length & make BBS of the Lintel bar.


Now, let us prepare a BBS table for the Chajja or sunshade.

Sl. No.

Type of Bar

Dia.

in mm.

Nos.

Length

in m.

Total length

in m.

Weight

in Kg/m.

Total

 bar wt.

in kg.

1.

Main bar.

10

11

1.45

15.95

0.612

   9.76

2.

Distribution bar.

8

7

1.46

10.22

0.395

   4.04 

3.

       Total weight of steel bars =

 13.80

4.

         Add 3% wastage =

   0.414 

5.

The grand total wt. of rebar's in sunshade =

14.21

 


Go through the article 👇

👀. Bar bending schedule (BBS) of a sunshade. (Type-2) 

Thank you for going through these calculation steps. Have a good day 😄.

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