Two type of load acts on column lateral load and axial load. When you will cut cross- section you will find six vertical bars. Out of which 4 is 25Ø and 2 is 16 Ø.
Floor to floor dimension is shown in figure above. Column clear length is 3m.
At top where column ends, there column outer reinforcement will go Ld (development length) distance in roof slab.
Ld= 50d, where d is dia of bar.
Column size= 300mm *600mm
Clear cover in column=40mm
Clear cover in footing=50mm
Clear cover in slab=30mm
Dia of Stirrup= 8mm
Here column we have divided in two zone. Now L/6 from top and bottom of is Zone A. Remaining at center there is Zone B. We always try column Lap always lie in Zone B not in Zone A. Because when load is applied on column moment is more at bottom in Zone A. So we avoid lap in Zone A. Spacing of Stirrup in Zone A is less than Zone B. See in figure above in L/6 portion spacing is 100c/c and in Zone B it is 150c/c.
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Vertical Bar Calculation:
Length of 20 Ø
= 300+ (1500-50-25-25)+600+200+(3000*4)+(175*3)+(50*20)-(2*2*20)+50*20
=16945 mm = 16.945 m>12m
Brief:
Length of 20 Ø = Ld+Footing depth – cover of footing- Main bar of footing- Bar of footing+depth upto ground floor+200+ Floor to Floor height*4+ (Slab thk *3)+ Development length- Two bend+ one lap
where Development length, Ld= 50d, Lap=50d, Bend=2d
Total no. of 20 Ø bar= 4
Total length of 20 Ø bar = 16.945 * 4= 67.78m
Length of 16 Ø
= 300+(1500-50-25)+600+200+(3000*4)+(!75*3)+(50*16)-(2*2*16)+(50*16)
=16586 mm = 16.586 m
Total no. of 16 Ø bar= 2
Total length of 16 Ø bar = 16.586 * 2= 33.172 m
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Cutting Length of Vertical Bars:
Lap distance from center of column is 75 mm. Hence end to end distance of lap is 150mm.
For 20 Ø
Part 1: 300+(1500-50-25-25)+600+200+(3000*2)+(175*2)+(1500-75)-1*2*20
=10235 mm = 10.235 m
where bend= 1*2*20, b’ = 1500-75= 1425mm
Part 2: (1500+75+1000)+175+3000+1000-(1*2*d)
= 6710 mm = 6.71m
where a’ = 1500 +75+Ld= 1500+75+1000= 2575 mm
Ld = 50 * 20 = 1000mm
For 16 Ø
Part 1 : 300+(1500-50-25)+600+200+b-bend
= 300+ (1500-50-25)+600+200+2375-(1*2*16)
=4868 mm or 4.868 m
where b= 1500 + 75 + (50*16) = 2375 mm
Part 2 : a+ (175*3)+ (3000*3)+Ld- (1*2*16)
=11718 mm = 11.718 m
where a= 1500- 75 = 1425 mm
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Cutting Length of Stirrups
a= 600-40*2-8/2-8/2= 512mm
b= 300-40*2-8/2-8/2= 212mm
Cutting length=(2*a)+(2*b)+(2*10*d)-(5*2*d), where hook=2*10d and bend = 5*2d
=(2*512)+(2*212)+(2*10*8)-(5*2*8)
=1528 mm = 1.528 m
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No of Stirrups: = Length/ spacing+1
Part A = 2700/100 +1 =28 nos
Part B = 2000/150 -1=12 Nos*4 = 48 Nos
Part C = 1175/100+1= 13 Nos *3 = 39 Nos
Part D = (650-30)/100+1= 7 Nos
Total Nos = A+B+C+D =122 Nos
