two way slab bbs with reinforcement details

To prepare two way slab bbs we have to calculate cutting length of bars, no. of bars to be provided and the weight of bars as the dia of bar will be known.

weight of bar formula = (d^2/162)*CL

where,

d = diameter of the bar

CL = cutting length of the bar

Slab reinforcement plan

two way slab bbs (reinforcement plan)

Slab Section

Given,

length = 60000mm

width = 2500mm

depth = 150mm

beam depth = 300mm

clear cover(cc) = 25mm

main bar = 20mm@150mm c/c

dist. bar = 16mm@150mm c/c

top extra bar = 10mm@150mm c/c

development length (Ld) = 40d

bends

45°=d

90°=2d

Main cranked bar

No. of bars = ((slab width – (2*cc))/spacing)+1

= ((4000-(2*25))/150)+1 = 27.3 ~ 28 nos.

Cutting Length = slab width+((2*beam depth)-(2*cc))+(0.42*(slab depth-(2*cc)-bar dia))-(2*bends)

= 4000+((2*300)-(2*25))+(0.42*(150-(2*25)-20))-(2*2*20) = 4503.6 ~ 4504mm

weight = ((d^2/162)*CL)/1000= ((20^2/162)*4504)/1000= 11.12 ~ 11.2Kg

Distribution cranked bar

No. of bars = ((slab length – (2*cc))/spacing)+1

= ((6000-(2*25))/150)+1 = 40.6 ~ 41 nos.

Cutting Length = slab length+((2*beam depth)-(2*cc))+(0.42*(slab depth-(2*cc)-bar dia))-(2*bends)

= 6000+((2*300)-(2*25))+(0.42*(150-(2*25)-16))-(2*2*16) = 6521.28 ~ 6522mm

weight = ((d^2/162)*CL)/1000= ((16^2/162)*6522)/1000= 10.30 ~ 10.3Kg

Top dist. & extra bars along longer span

Top distribution bar (longer span)

No. of bars = ((slab width/5/spacing)+1)*2

= ((4000/5/150)+1)*2 = 12.6 ~ 13 nos.

Cutting Length = slab width+2Ld

= 4000+(2*40*10) = 4800mm

weight = ((d^2/162)*CL)/1000= ((10^2/162)*4800)/1000= 2.96 ~ 3Kg

Top Extra bar (longer span)

No. of bars = ((slab width – ((slab width/5)*2))/spacing)+1)*2

= ((4000-((4000/5)*2))/150)+1)*2 = 34 nos.

Cutting Length = (slab width/5)+2Ld

= (4000/5)+(2*40*10) = 1600mm

weight = ((d^2/162)*CL)/1000= ((10^2/162)*1600)/1000= 0.987 ~ 1Kg

Top dist. & extra bars along shorter span

Top distribution bar (shorter span)

No. of bars = ((slab length/5/spacing)+1)*2

= ((6000/5/150)+1)*2 = 18 nos.

Cutting Length = slab length+2Ld

= 6000+(2*40*10) = 6800mm

weight = ((d^2/162)*CL)/1000= ((10^2/162)*6800)/1000= 4.197 ~ 4.2Kg

Top Extra bar (shorter span)

No. of bars = ((slab length – ((slab length/5)*2))/spacing)+1)*2

= ((6000-((6000/5)*2))/150)+1)*2 = 50 nos.

Cutting Length = (slab length/5)+2Ld

= (6000/5)+(2*40*10) = 2000mm

weight = ((d^2/162)*CL)/1000= ((10^2/162)*2000)/1000= 1.23 ~ 1.3Kg

two way slab bbs table

Sl. No.DescriptionBar Dia (mm)Spacing (mm)CL (mm)No. of barsTotal Weight (Kg)
1main cranked bar20150450428313.6
2distribution cranked bar16150652241422.3
3top dist. bar (longer span)1015048001339
4top extra bar (longer span)1015016003434
5top dist. bar (shorter span)1015068001875.6
6top extra bar (shorter span)1015020005065

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