**How to calculate cutting length of reinforcement (steel) used in column,****bar bending schedule of column,**in this topic we know about how to calculate cutting length of reinforcement (rebar) used in column and bar bending schedule of column.

We know that column is RCC structure and important structural part of any project which transfer load acting on it by different structure to the the bed of soil. Let us discuss about bar bending schedule of column in which we find cutting length of reinforcement used in column and estimate the requirement of reinforcement in column.

Column is vertical structural component which is stand on mesh bar of footing in ground soil.

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** how to calculate cutting length of reinforcement (steel) used in column and BBS of column**

**Cutting length of reinforcement used in column = longitudinal length of column + development length of column in Roof of slab and in footing + lapping length+parapet wall _ bend elongation**

**1) longitudinal length of column**

In given diagram we have following

Thickness of footing = 300mm

Length to plinth beam= 1000 mm

Thickness p.beam = 300 mm

P.beam to roof = 3000 mm

Thickness of slab = 120 mm

Total H = 300+1000+300+3000+120 mm

Total height = 4720 mm

Total deduction of clear cover

A) clear cover in footing

Clear cover = Fc = 40 mm

Two dia of mesh bar =8+8 =16mm

Total clear cover = 40+16=56mm

B) clear cover in roof slab

Which is Rc = 25 mm

Total clear cover = Fc +Rf +16

Total clear cover = 40+25+16 mm

Total clear cover = 81 mm

Longitudinal bar = total height _ total clear cover

Longitudinal bar = 4720_81 mm

Length of one longitudinal bar = 4639 mm

**calculate development length of reinforcement in column**

A) Development length in roof slab is

Ld = 40d where d is dia of reinforcement used in column that is 12 mm

Ld = 40×12 = 480 mm

B) development length in footing

Development length in footing that is Ld is equal to 300 mm which is given

Ld in footing = 300 mm

Total development length in roof slab and in footing

Ld = 480+300=780 mm

**3) calculation of lapping length**

In given diagram that is BBS of column only for ground floor building, we know that lapping is provided in middle part of column. 1 reinforcement length is about 12 metre so there is no needs of lapping length provided for ground floor building

**4) calculation of parapet wall length**

In given diagram that is BBS of column only for ground floor building so column is not provided in upper part of roof slab so length of parapet wall for column is equal to zero in this BBS of column.

**5) bend elongation calculation**

We know that when reinforcement it is bend then it will stretch and increase in length for calculating BBS of column and cutting length of reinforcement used in column, bend elongation is deducted, in given diagram reinforcement in column bend position 1 in roof slab and second one in footing at the 90 degree angle.

For bend 90° we have 2d

Bend elongation= 2×2d

Bend elongation=2×2×12=48mm

** cutting length of reinforcement used in column**

Cutting length of reinforcement used in column = longitudinal length of column + development length of column in Roof of slab and in footing + lapping length+parapet wall _ bend elongation

Where longitudinal length =4639 mm

Total development length = 780 mm

Lapping length = 00 mm

Parapet wall length =00 mm

Bend elongation = 48mm

CL = (4639 +780+0+0)_(48) mm

Cutting length of 1 steel = 5371 mm

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**BBS of column and bar bending schedule**

If we provide 6 number of bar of 12 mm dia of reinforcement used in column

**1) total cutting length (Tcl) for 6 nos**

Tcl = 6×5371 mm

Total cutting length = 32226mm

Now we convert millimetre into metre

Total cutting length= 32.226 meter

** Total weight of Steel required for one column**

We have one formula for approx calculation for estimate and quantity of reinforcement

Weight=( D^2/162) length kg

Weight = (12×12)/162 (32.226) kg

Weight = 28.645 kg for one column

If we have 10 column than

Total weight = 286.45 kg

** calculate total number of stirrups in rectangular column**

The Ring used in column provide lateral support to the the main bar against buckling it is used at proper interval to beam and column to prevent them from buckling. Also they protect RCC structure from collapsing during seismic activity like earthquake. It is used to resist lateral shear stress and diagonal tension stress in RCC structure and provide stability to the reinforcement of Steel bar.

No. of stirrups = (longitudinal length/spacing)+1

We have longitudinal length=4639 mm

Spacing of stirrup = 150 mm

No. of stirrups= (4639/150)+1

No. of stirrup = 30.92 +1 =31.92

We rounded off 31.92 as 32

So we have required 32 number of stirrup for tie reinforcement used in rectangular column

Md. Ali Akbar says

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