PARAM VISIONS

All about civil construction knowledge- PARAM VISIONS

Bar bending schedule (BBS) of a retaining wall. / Calculating the cutting length & weight of reinforcement in a retaining wall.

Let us make BBS of the retaining wall as shown below.

Given data:

Retaining wall length = 9000mm.= 9m.

Raft width = 2150mm.

Raft depth = 400mm.

Wall height = 2500mm.

Wall width = 300mm

Clear cover = 50mm.

Calculation:

A. Cutting length:

1. Main bar of raft:

Given data:

Reinforcement = T16 @ 150 c/c.

Overlap = 150mm.

Cutting length of raft main bar

= [{2nos.×( a +  b + overlap)} - (5nos. × 90° bend)]

Where, a

= [raft width - (2nos. × cover)]

= [ 2150mm. - (2nos. × 50mm.)]

a = 2050mm.

b  = [raft depth - (2nos. × cover)]

= [ 400mm. - (2nos. × 50mm.)]

b = 300mm.

Cutting length of raft main bar

= [{2nos.×( 2050mm. +  300mm.+ 150mm.)} - (5nos. × 2d)]

= [ {2nos.× 2500mm} - (5nos. × 2 × 16mm)]

= [ 5000mm - 160mm.]

= 4840mm.

= 4.84m.

2. Distribution bar of raft:

Cutting length of distribution bar of the raft

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

= [ 9000mm. - (2nos. × 50mm.)]

= 8900mm.

= 8.90m.

3. Main bar of RCC wall:

3a. Inner vertical bar:

Given data:

Reinforcement = T16 @ 150 c/c.

Cutting length of the inner vertical bar

= [(300mm.+ a + 150mm.)- (2nos. × 90° bend)]

Where

a = [(wall height - cover) + (raft depth - cover)]

=  [(2500mm. - 50mm.) + (400mm. - 50mm.)]

= [2450mm. + 350mm.]

a = 2100mm.

Cutting length of the inner vertical bar

= [(300mm.+ 2100mm. + 150mm.) - (2nos. × 2d)]

= [ 2550mm- (2nos. × 2 × 16mm.)]

= [2550mm. - 64mm.]

= 2486 mm.

= 2.486m.

3b. Outer vertical bar:

Given data:

Reinforcement = T12 @ 150 c/c.

Cutting length of the outer vertical bar

= [(300mm.+ a + 150mm.)- (2nos. × 90° bend)]

Where

a = [(wall height - cover) + (raft depth - cover)]

=  [(2500mm. - 50mm.) + (400mm. - 50mm.)]

= [2450mm. + 350mm.]

a = 2100mm.

Cutting length of the outer vertical bar

= [(300mm.+ 2100mm. + 150mm.) - (2nos. × 2d)]

= [ 2550mm- (2nos. × 2 × 12mm.)]

= [2550mm. - 48mm.]

= 2502 mm.

= 2.5m.

4. Distribution bar of wall:

Cutting length of distribution bar of the wall

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

= [ 9000mm. - (2nos. × 50mm.)]

= 8900mm.

= 8.90m.

Cutting length of the link bar

= [a + (2nos. × 75mm.) - (2nos. × 90° bend)]

Where

a = [ wall width - (2nos.× cover)]

= [300mm.- (2nos.× 50mm.)]

a = 200mm.

Cutting length of the link bar

= [200mm + (2nos. × 75mm.) - (2nos. × 2 × 8mm.)]

= [200mm. + 150mm. - 32mm.]

= 318mm.

= 0.318m.

B. No of bars:

1. Main bars of the raft:

No. of main bars in the raft

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

= [{9000mm. - (2nos. × 50mm.)}÷ 150mm.] + 1

= [8900mm. ÷ 150mm.] + 1

= 59.33 +1

= 60.33

By rounding off = 61nos.

2. Distribution bars of the raft:

No. of  distribution bars in the raft

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

= [{2150mm. - (2nos. × 50mm.)}÷ 150mm.] + 1

= [2050mm. ÷ 150mm.] + 1

= 13.66 +1

= 14.66

By rounding off = 15nos.

The distribution bars are provided at the top & bottom sides of the raft.

So, the total no. of distribution bars in the raft

= [2sides × 15nos.]

= 30 nos.

3a. Inner vertical bar

No. of inner vertical bars in the wall

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

= [{9000mm. - (2nos. × 50mm.)}÷ 150mm.] + 1

= [8900mm. ÷ 150mm.] + 1

= 59.33 +1

= 60.33

By rounding off = 61nos.

3b. Outer vertical bar

No. of outer vertical bars is the same as inner vertical bars

= 61 nos.

4. Distribution bars of wall:

No. of  distribution bars in the wall

= [{wall depth - cover}÷ c/c distance] + 1

= [{2500mm. - 50mm.}÷ 150mm.] + 1

= [2450mm. ÷ 150mm.] + 1

= 16.33 +1

= 17.33

By rounding off = 18nos.

The distribution bars are provided at the inner & outer sides of the wall.

So, the total no. of distribution bars in the wall

= [2sides × 18nos.]

= 36 nos.

Link bars are provided along the length side & height of the wall as shown in the above drawing.

No. of link bars along the length side

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

= [{9000mm. - (2nos. × 50mm.)}÷ 300mm.] + 1

= [8900mm. ÷ 300mm.] + 1

= 29.67 +1

= 30.67

By rounding off = 31nos.

No. of link bars along the height side

= [{wall height - cover}÷ c/c distance] + 1

= [{2500mm. - 50mm.}÷ 300mm.] + 1

= [2450mm. ÷ 300mm.] + 1

= 8.16 +1

= 9.16

By rounding off = 10nos.

Total no. of link bars required for retaining wall

= [along length side  × along height side]

= [ 31nos.× 10nos.]

= 310nos.

To know, how to calculate the concrete volume, Go through the article ðŸ‘‡

Now, let us prepare a BBS table for the retaining wall.

 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 of raft 16 61 4.84 295.24 1.578 465.89 2. Distribution bar of raft. 10 30 8.90 267 0.617 164.74 3. Main bar of wall 3a. Inner vertical bar. 16 61 2.486 151.65 1.578 239.30 3b. Outer vertical bar. 12 61 2.50 152.50 0.888 135.42 4. Distribution bar of wall. 10 36 8.90 320.40 0.617 197.69 5. Link bar 8 310 0.318 98.58 0.395 38.94 6. Total weight of bars = 1241.98 7. Add 3% wastage = 37.26 8. The grand total wt. of rebar's = 1279.24

Thank you for going through these calculation steps. Have a good day ðŸ˜„.