A 105 M Wide Continuous Footing is Designed to Support an Axial Column Load of 200kn Chegg
How to calculate axial load carrying capacity of column, u ltimate load carrying capacity of column, in this topic we know about how to calculate axial load carrying capacity of column. Axial load depends on type of reinforcement used in column and size of column.
Axial load is structural load that is beam slab and brick wall that's acts on longitudinal axis on column. Axial loading of column means load is acting on longitudinal axis of column this produces no any moment.
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When load is not acting on longitudinal axis of column it will produce bending moment. If bending moment is takes place in only one axis on column than it will be unaxial load and if bending moment is takes along two axis acting on column than it will be biaxial load.
But in this calculation we only calculate axial load carrying capacity of column.
- determine axial load carrying capacity of rectangular column having size 300× 400 mm and reinforced with 6 nos of Steel bar of 20 mm dia and grade of concrete is M20 and steel is Fe415.
How to calculate axial load carrying capacity of column
◆Given :-
Size of rectangular column = 300mm×400 mm
Grade of concrete = M20
fck = characteristics of comprehensive strength of concrete = 20 N/mm2
Grade of steel = Fe415
fy = yield strength or ultimate tensile strength of Steel = 415 N/mm2
Number of steel bar = 6 nos
Diameter of Steel bar = 20 mm
axial load carrying capacity of column formula
Pu = 0.4fck.Ac + 0.67fy.Asc
as per IS code 456 2000
Where Pu = ultimate axial load carrying capacity of column
fck = characteristics of comprehensive strength of concrete which is given
Ac = area of concrete in column which will be calculated
Asc = area of Steel in column which will be calculated
So we have to following find the value
1) Ac = ? Area of concrete
2) Asc = ? Area of steel
3) Pu = ? Axial load carrying capacity
◆ Solve
1) first we have to calculate gross cross sectional area of column
Ag = gross cross sectional area of column
Size of column = 300×400 mm
Ag = 300×400 mm2
Ag = 120000 mm2
2) second we have to calculate area of Steel in column
Asc = area of Steel in column
No. of steel bar = 6 nos
Diameter of Steel bar D = 20 mm
Area of bar = 6×π/4× D2
Where π = 3.14
Asc = 6× (3.14/4) 20×20 mm2
Asc = 1884 mm2
3) now we calculate area of concrete in column
Ac = area of concrete in column
We know that gross cross sectional area of column is equal to area of concrete in column and area of Steel in column
Ag = Ac + Asc
Ac = Ag _ Asc
Putting the value of gross area of column and steel area subtracting both we get concrete in column
Ac = 120000_1884 mm2
Ac = 118116 mm2
Putting all the value in formula for ultimate axial load carrying capacity of column
Pu = 0.4fck.Ac + 0.67fy.Asc
Where , fck = 20 N/mm2
Ac = 118116 mm2
fy = 415 N/mm2
Asc = 1884 mm2
Pu = (0.4× 20×118116) N +(0.67×415×1884) N
Pu = 944928 N + 523846 N
Pu = 1468774 N
Converting into kilo Newton we have to divide by 1000
Pu = 1468774 N/1000 =1468.774 KN
Hence about 1468.774 KN ultimate axial load carrying capacity of column for above this calculation.
Load carrying capacity of column
Load carrying capacity of column will depend upon the percentage of steel reinforcement, grade of concrete and column size for various mixes and steel.
For steel grade fy 415
Concrete grade & Axial Load carrying Capacity of column in KN (P)
M15, P= (2.7205 p + 6) b D/1500
M20, P= (2.7005 p + 8) b D/1500
M25, P= (2.6805 p + 10) b D/1500
M30, P= (2.6605 p + 12) b D/1500
M35, P= (2.6405 p + 14) b D/1500
M40, P= (2.6205 p + 16) b D/1500
For steel grade fy 500
Concrete grade & Axial Load carrying Capacity of column in KN (P)
M15, P= (3.29 p + 6) b D/1500
M20, P= (3.27 p + 8) b D/1500
M25, P= (3.25 p + 10) b D/1500
M30, P= (3.23 p + 12) b D/1500
M35, P= (3.21 p + 14) b D/1500
M40, P= (3.19 p + 16) b D/1500
For steel grade fy 550
Concrete grade & Axial Load carrying Capacity of column in KN (P)
M15, P= (3.625 p + 6) b D/1500
M20, P= (3.605 p + 8) b D/1500
M25, P= (3.585 p + 10) b D/1500
M30, P= (3.565 p + 12) b D/1500
M35, P= (3.545 p + 14) b D/1500
M40, P= (3.525 p + 16) b D/1500
Note :-
1. The axial Load carrying capacity column is arrived based on the formula
Pu =0.4 fck Ac + 0.67 fy Asc as per IS 456-2000.
2. Here in the Table P is Axial Load Carrying capacity of column in KN.
p is steel in percentage say percentage as 1
b is breadth of column in mm
D is depth of column in mm.
For preliminary design use square columns.
If the building height is 3 stories or less:
If beam span < 6000mm, h (mm) = 300
If 6000 < beam span < 9000, h = 350
If 9000 < beam span < 12000, h = 400
If the building height is 4 to 9 stories:
If beam span < 6000mm, h (mm) = 400
If 6000 < beam span < 9000, h = 500
If 9000 < beam span < 12000, h = 600
1) calculate self load of column
2) calculate self load of beam per metre
3) calculate slab load per square metre
4) calculate dead load of brick wall per metre
5) ultimate load carrying capacity of column
Now we have to few things remember
what is fck in concrete?
It is comprehensive strength of concrete define as characteristics comprehensive strength of 150 mm cube size in 28 days. in designing process 5% of specimen tested are expected to fail if more than 5% of specimen is fail is said to be fail under the test result.
suppose we have 100 cube of 150 mm size of M20 grade 95 cube should be able to with stand a comprehensive load of 20 Newton per mm square if not more than 5% fail than grade of M20 of concrete design is said to be pass under the test result.so fck is characteristics of comprehensive strength of concrete like that for M20and M25 fck is 20N/mm2 and 25N/mm2 respectively.
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You should also visits:-
1)what is concrete and its types and properties
2) concrete quantity calculation for staircase and its formula
3) how to calculate weight of mild steel plate and derive its formula
what is fy in steel
It is yield strength and ultimate tensile strength of various types of Steel denoted by fy steel have many grade like Fe250,Fe415,Fe500 and Fe 250 is low yield strength present in mild steel and Fe415 Fe500 have high yield strength used in formation of column.
Source: https://civilsir.com/how-to-calculate-axial-load-carrying-capacity-of-column/
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