**Column size for 5m span | How to calculate the size of column**, hi guys in this article we know about what is standard size of column column size for 5m span and how to calculate the size of column.

In this article we are giving some Thumb Rule which might be helpful in deciding size of column. It is necessary for every civil engineer and architectural engineer when decide to designing of column size and their reinforcement.

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**1)what is concrete and its types and properties**

**2) concrete quantity calculation for staircase and its formula**

As know that column is compressive member of RCC concrete provided with good amount of reinforcement transfer all incoming load safely to bed of soil. So column is load bearing structure resist all incoming load from superstructure of project. All the load of slab and Beem transfer to column through column beam joint.

**Size of column depend** on total load applied on the column, alignment of column and span between two column, in this topic we try to find out column size for 5 metre span. The size of the columns depends on the total load on the columns. There are axial loads and lateral loads.

Large beam spans induce bending moment not only in the beams, but also in columns which are pulled by the stresses in the beams. Also go through building codes to get better advice about the sizes of column as per loads going to come on it . Because the sizes varies according to load and function of structures.

Column size depends on various factors like number of floors, span between two column, is it short or slender, For 5m span 1 storey/single floor/ground floor/G+0 residential building, it could be 230×230, for G+1 it could be 230x 300mm, for G+2 it could be 300x 300mm,for G+3 it could be 300x 380mm and for G+4 it could be 380x 450mm using M20 grade of concrete ratio 1:1.5:3 with Fe500 grade of steel when a tributary area 15m×15m and span between each column is 5m consists of 16 column.

A reinforced concrete column is a structural member designed to carry compressive loads, composed of concrete with an embedded steel frame to provide reinforcement. For design purposes, the columns are separated into two categories: short columns and slender column.

**What is the standard size of column?** The minimum size of rcc column should not be less than 9”x9” for single story (G+0) structure with M20 (1:1.5:3) concrete. We recommended Standard size of column is 9”x 12” are to be used in one and half story building, always use M20 (1:1.5:3) concrete and 4nos of T12 of Fe 500 steel with stirrup T8@6″C/C.

**How to calculate the size of column?**

While we are going through designing of column size have 5metre span for G+2 ( 3 storey residential commercial building) require some basic concept about IS code 456:2000 their recommendation are following:-

**IS 456:2000 recommendation for designing of column**

1) minimum clear cover for column 40mm is provided, if size of column is less than 200mm then clear cover is 25mm is provided.

2) minimum diameter of bar 4 nos of 12mm should be taken

3) minimum area of Steel =0.8%of Ag

Maximum area of Steel=6%of Ag ( Steel should not overlap) 4%of Ag if steel is overlap

4) maximum spacing between two longitudes renforcement shall not greater than 300 mm

5) minimum dia of Stirrup 1/4×16 greater

6) maximum spacing of stirrup 16D, B and 300mm which ever is minimum.

As we know total load coming on column calculated according to actual design of given structure. But in general taking Thumb Rule for designing of column For a Residential Building max load intensity applied on column = 15kN/m2 -20kN/m2.

We assuming a span of 5m x5m span in both sides of the column. (imagine the column in plan view and and from the center of the column to another column is 5m in both horizontal and vertical direction) and total span of slab 15m×15m consist of 5 metre span between each column. Total number of column support is 16.

We use M20 grade of concrete, with cement sand aggregate ratio 1:1.5:3, providing a reinforcement of Fe500.

While designing and during the alignment of column there is some mistakes so ideal ultimate axial load is not possible, it is eccentric. IS 456: 2000 clause 39.3 page no 71 recommend that using Pu=0.4fck.Ac + 0.67fy.Asc formula to be used while deciding the column size during ecentric condition.

**Ultimate axial load acting on column given by this formula**

**Pu=0.4fck.Ac + 0.67fy.Asc**

Where Pu = ultimate axial load

fck = characteristics of compressive strength of concrete

Ac = Area of concrete in column

Asc = Area of steel in Column

Ag = Gross area of column.

IS 456: 2000 suggesting minimum area of Steel =0.8%of Ag,Maximum area of Steel=6%of Ag ( Steel should not overlap) 4%of Ag if steel is overlap.

Suppose gross area Ag =100%

Steel area Asc =1%ofAg =0.01Ag

Concrete area Ac =99%of Ag =0.99Ag.

We have the tributary area = 15m x 15m,

Number of floors = 3, fck =20N/mm2, fy =500N/mm2, total number of column =16, span size 5m.

Total axial load acting on all column = no of floor × thumb rule 20kN/m2 × slab span

Load = 3×20kN/m2 ×15m×15m = 13500kN

Load acting on each column=13500kN/16=844kN

Consider 10% increasing load on each column for safety factor, 10% of 844 =85kN, so total axial load acting on each column=844+85= 929kN, putting this value in in formula.

Pu=0.4fck.Ac + 0.67fy.Asc

929kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

929×10^3 = 7.92Ag +3.35Ag

929×10^3 = 11.27Ag

Ag (Gross area=929×10^3/11.27=82431mm2

Suppose we square column, so area of square =a2, hence a2 = 82431mm2, a=√82431mm2=286mm.

Width and depth of column =286mm×286mm, taking in round figure=300mm×300mm(12″×12″).

According to column design and Thumb Rule, column size for 5m span is 300mm×300mm (12″×12″) for 3 storey (G+2) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 929kN is applied on each column.

**Column size for 5m span**

**Column size for 5m span for 1 storey/single floor/Ground floor/G+0 residential building:-**

1) Calculating column size for 5m span for 1 storey/single floor/ground floor/G+0 residential building, we have given number of floor=1, total number of column = 16, fy=500N/mm2, fck=20N/mm2, thumb rule load=20kN/m2, gross area Ag =100%, steel area Asc =1%ofAg =0.01Ag and concrete area Ac =99%of Ag =0.99Ag.

Load = 1×20kN/m2 ×15m×15m = 4500kN,

Load acting on each column=4500kN/16=281kN, consider 10% increasing load on each column for safety factor, 10% of 281 =28kN, so total axial load acting on each column=281+28= 310kN, putting this value in in formula,

Pu=0.4fck.Ac + 0.67fy.Asc,

310kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

310×10^3 = 7.92Ag +3.35Ag

310×10^3 = 11.27Ag

Ag (Gross area=310×10^3/11.27=27506mm2,

Suppose we square column, so area of square =a2, hence a2 = 27506mm2, a=√27506mm2=165mm, width and depth of column =165mm×265mm, taking in round figure=230mm×230mm(9″×9″).

According to column design and Thumb Rule, minimum column size for 5m span is 230mm×230mm (9″×9″) for 1 storey/single floor/ground floor/(G+0) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 310kN is applied on each column.

**Column size for 5m span for 2 storey/two floor/G+1 residential building:-**

2) Calculating column size for 5m span for 2 storey/two floor/G+1 residential building, we have given number of floor=2, total number of column = 16, span area=15m×15m, fy=500N/mm2, fck=20N/mm2, thumb rule load=20kN/m2, gross area Ag =100%, steel area Asc =1%ofAg =0.01Ag and concrete area Ac =99%of Ag =0.99Ag.

Load = 2×20kN/m2 ×15m×15m = 9000kN,

Load acting on each column=9000kN/16=563kN, consider 10% increasing load on each column for safety factor, 10% of 563 =56kN, so total axial load acting on each column=563+56= 619kN, putting this value in in formula,

Pu=0.4fck.Ac + 0.67fy.Asc,

619kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

619×10^3 = 7.92Ag +3.35Ag

619×10^3 = 11.27Ag

Ag (Gross area=619×10^3/11.27=54925mm2,

Suppose we square column, so area of square =a2, hence a2 = 54925mm2, a=√54925mm2=234mm, width and depth of column =234mm×234mm, taking in round figure=230mm×300mm(9″×12″) for rectangular column.

According to column design and Thumb Rule, minimum column size for 5m span is 230mm×300mm (9″×12″) for 2 storey/two floor/(G+1) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 619kN is applied on each column.

**Column size for 5m span for 3 storey/three floor/G+2 residential building:-**

3) Calculating column size for 5m span for 3 storey/three floor/G+2 residential building, we have given number of floor=3, total number of column = 16, span area=15m×15m, fy=500N/mm2, fck=20N/mm2, thumb rule load=20kN/m2, gross area Ag =100%, steel area Asc =1%ofAg =0.01Ag and concrete area Ac =99%of Ag =0.99Ag.

Load = 3×20kN/m2 ×15m×15m = 13500kN,

Load acting on each column=13500kN/16=844kN, consider 10% increasing load on each column for safety factor, 10% of 844 =85kN, so total axial load acting on each column=844+85= 929kN, putting this value in in formula,

Pu=0.4fck.Ac + 0.67fy.Asc,

929kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

929×10^3 = 7.92Ag +3.35Ag

929×10^3 = 11.27Ag

Ag (Gross area=929×10^3/11.27=82431mm2,

Suppose we square column, so area of square =a2, hence a2 = 82431mm2, a=√82431mm2=287mm, width and depth of column =287mm×287mm, taking in round figure=300mm×300mm(12″×12″) for square column.

According to column design and Thumb Rule, minimum column size for 5m span is 300mm×300mm (12″×12″) for 3 storey/three floor/(G+2) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 929kN is applied on each column.

**Column size for 5m span for 4 storey/four floor/G+3 residential building:-**

4) Calculating column size for 5m span for 4 storey/four floor/G+3 residential building, we have given number of floor=4, total number of column = 16, span area=15m×15m, fy=500N/mm2, fck=20N/mm2, thumb rule load=20kN/m2, gross area Ag =100%, steel area Asc =1%ofAg =0.01Ag and concrete area Ac =99%of Ag =0.99Ag.

Load = 4×20kN/m2 ×15m×15m = 18000kN,

Load acting on each column=18000kN/16=1125kN, consider 10% increasing load on each column for safety factor, 10% of 1125 =113kN, so total axial load acting on each column=1125+113= 1238kN, putting this value in in formula,

Pu=0.4fck.Ac + 0.67fy.Asc,

1238kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

1238×10^3 = 7.92Ag +3.35Ag

1238×10^3 = 11.27Ag

Ag (Gross area=1238×10^3/11.27=109850mm2,

Suppose we square column, so area of square =a2, hence a2 = 109850mm2, a=√109850mm2=331mm, width and depth of column =331mm×331mm, taking in round figure=300mm×380mm(12″×15″) for rectangular column.

According to column design and Thumb Rule, minimum column size for 5m span is 300mm×380mm (12″×15″) for 4 storey/four floor/(G+3) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 1238kN is applied on each column.

**Column size for 5m span for 5 storey/five floor/G+4 residential building:-**

5) Calculating column size for 5m span for 5 storey/five floor/G+4 residential building, we have given number of floor=5, total number of column = 16, span area=15m×15m, fy=500N/mm2, fck=20N/mm2, thumb rule load=20kN/m2, gross area Ag =100%, steel area Asc =1%ofAg =0.01Ag and concrete area Ac =99%of Ag =0.99Ag.

Load = 5×20kN/m2 ×15m×15m = 22500kN,

Load acting on each column=22500kN/16=1406kN, consider 10% increasing load on each column for safety factor, 10% of 1406 =141kN, so total axial load acting on each column=1406+141= 1547kN, putting this value in in formula,

Pu=0.4fck.Ac + 0.67fy.Asc,

1547kN=0.4 ×20×0.99Ag + 0.67×500×0.01Ag

1547×10^3 = 7.92Ag +3.35Ag

1547×10^3 = 11.27Ag

Ag (Gross area=1547×10^3/11.27=137267mm2,

Suppose we square column, so area of square =a2, hence a2 = 137267mm2, a=√137267mm2=370mm, width and depth of column =370mm×370mm, taking in round figure=300mm×450mm(12″×18″) for rectangular column.

According to column design and Thumb Rule, minimum column size for 5m span is 300mm×450mm (12″×18″) for 5 storey/five floor/(G+4) residential building using M20 grade of concrete ratio (1:1.5:3) with Fe500 grade of steel when axial load 1547kN is applied on each column.