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
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