Last Updated on

__STEP 1 :- ____Calculation of the Influence Area for Design of Columns :__

__STEP 1 :-__

__Calculation of the Influence Area for Design of Columns :__

__STEP 2:- ____Calculation of the Loads Coming on Columns from the Influence Area :__

__STEP 2:-__

__Calculation of the Loads Coming on Columns from the Influence Area :__

__A)Dead Loads :__

^{3 }]

^{2}]

^{3}]

^{3}]

^{3}]

__B) Live Load :__

It depends upon the Nature of the Structure, and it values for different structural nature are given in the concerned Code of Practice, like in India these are given in I.S.: 875-Part II.

^{2}= 2000 N/m

^{2}

COLUMN FORM WORK OF BUILDING |

Now after correct calculation of above loads the Total Load is Calculated by,

__STEP 3 :-____Finding The Gross Cross-Sectional Area Required For The Design of Columns :__

__STEP 3 :-__

__Finding The Gross Cross-Sectional Area Required For The Design of Columns :__

_{u.}

_{u}= 1.5 X P

_{u}= 0.4.f

_{ck}.A

_{c}+ 0.67.f

_{y}.A

_{sc}[Equation I]

_{u}= Ultimate Load of the Column in N/mm

^{2}

_{ck}= Yield Strength of Concrete in N/mm

^{2}

_{c }= Area of Concrete (Cross-Sectional Area) of Column in mm

^{2}

_{y }= Yield Strength Of Steel in N/mm

^{2}

_{sc}= Area of Steel (Cross-Sectional Area) in Column in mm

^{2}

_{g}.

_{g}= A

_{c}+ A

_{sc}

_{c}= A

_{g}– A

_{sc}

_{u}= 0.4.f

_{ck}.(A

_{g}-A

_{sc}) + 0.67.f

_{y}.A

_{sc }[Equation II]

_{g}). Say Assuming Steel as 1% of A

_{g}it means Area of Steel A

_{sc}= 1% of A

_{g}= 0.01A

_{g}

_{g}and thus lesser will be the cross-sectional dimension of the column. But the as the Price of Steel is very high as compared to the Concrete hence it is desirable to use as less as steel possible to make the structure economical, again if the percentage of steel is lowered then the A

_{g }will increase at higher rate, about 30% with decrease of just 1% of steel and so each lateral dimension of the column will increase and will cause a gigantic section to be provided to resist the load. Therefore both the factors are to be considered depending upon the amount of loading.

__Loading (P___{u}) in N __Percentage Of Steel for Satisfactory Design__

__Loading (P__

_{u}) in N__Percentage Of Steel for Satisfactory Design__

_{sc}in the form of A

_{g }in the Equation I. For example suppose 1% Steel is used then the equation will be like the one below :-

_{u}= 0.4.f

_{ck}.(A

_{g}-0.01A

_{g}) + 0.67.f

_{y}.0.01A

_{g}

_{g}) of the Column required from the above form of the equation.

_{g}or Gross-Sectional Area of the Column means that it is the product of the two lateral sides of a column [i.e. Breadth (b) X Depth (D)], hence reversely knowing the A

_{g}we can determine the Lateral Dimensions.

_{g}. Like if the Value of A

_{g}is 62500 mm

^{2}Then considering square section of a column we can get each side

_{g}= b X D = b X 2b = 2b

^{2}or b=

__STEP 4 : ____Check For Long/Short Columns: __

__STEP 4 :__

__Check For Long/Short Columns:__

__STEP 5____ Check For Eccentricity for Design of Columns :__

__STEP 5__

__Check For Eccentricity for Design of Columns :__

The Permissible eccentricity must be greater than or equal to the actual eccentricity of the column. Or else we have to design it for bending also.

__STEP 6 :-____Calculating The Area Of Steel Required for Design of Columns :__

__STEP 6 :-__

__Calculating The Area Of Steel Required for Design of Columns :__

_{sc }is to be calculated from the A

_{g}as the predetermined percentage of A

_{g}. For example if the Gross-Sectional Area of the Column is 78600 mm

^{2}and at the starting of calculation of Ag it was assumed that 1% Steel is used then we get,

_{sc}= 1% of A

_{g}= 0.01A

_{g}= 0.01 X 78600 = 786 mm

^{2}

__NOTE : The minimum of 4 Nos. of Bars to be provided at the four corners of a rectangular or Square Columns and minimum diameter of Bars that to be used is 12mm Diameter. Hence 4 Nos. of 12mm Diameter Bars are must in any Columns irrespective of their necessities.____STEP 7 :-____Determining The Diameter and Spacing Of The Lateral Ties for Design of Columns:__

__STEP 7 :-__

__Determining The Diameter and Spacing Of The Lateral Ties for Design of Columns:__

- 6mm
- 1/4
^{th}of the Diameter of the Largest Diameter Bar

^{th }of 20mm = 5mm Hence we shall provide 6mm diameter Ties.

- Least Lateral Dimension
- 16 Times of the Diameter of the Smallest Diameter Longitudinal Bar
- 48 Times of the Diameter of Ties

- Least Lateral Dimension = 250mm
- 16 Times of the Diameter of the Smallest Diameter Longitudinal Bar = 16 X 16 = 256mm
- 48 Times of the Diameter of Ties = 48 X 6 = 288mm

[In this case our objective is to minimize the value to reduce the spacing and to make the structure more stable, hence we shall take least value and suitably in a multiple of 25mm]

If you like this Article then I am sure you will like the following well researched articles too, come on check them out also

Thank you ðŸ™‚ no one can explain this in such a easy way.. as a fresher it helps me a lot.. seriously waiting for your new posts ðŸ™‚ it would be good if u explain about design of beam,colum,steel quantity. it will be greater helpful for freshers who jus entered the civil field

My Pleasure Buddy, if it helped you to understand it easily then it is my success for as because it was the main intention of writing this article. Keep Visiting Techno Genome and explore, you will find more and more articles which will help you out in understanding different concepts.

Thank you so much i get so many knowledge in your blog , do you also have quantity estimation or cost estimation.?

My Pleasure Eng Maxameddeeq Muuse , Quantity Surveying is not a single topic related thing to study, like design of column, beam, stair etc. all of them are independent of others mostly, but for Estimating we have to use most of the topic collectively for solving a single case. for now I have not written article on those but soon will be writing, have a plan to cover Estimating & Costing and STAAD Pro v8i. As You see it is not a copy-paste work, it takes some time to produce a Good Article so that any one can understand it. Keep visiting Techno Genome, I will be posting new topics at regular interval, who knows may be on the next article your wish becomes true ðŸ™‚ . . . . .Thanks For Commenting. . . . .

Good work (Top 5 Concreting Problems).

Dear sir,

I want to know how to calculate the incoming load on each column….because if there are 10 columns in each floor how to take the load distributed among all the columns…I think you get that

Please comment on proper article

Look add the newly added picture under the Influence Area of Column that is the step 1, It's very simple just draw the centre line diagram of the columns with dimensions, and draw lines between all adjacent columns from mid distance, then you will found a intersected portion, which are the required Influence Areas of the Columns

hello sir,

how to calculate spacing distance between two column..

Sorry For my late reply @Pavan, Please check the first image at the start of this article

such a nice work…. Really Hats off man. ðŸ™‚

what if the column has moment load?

Please help me solve this problem.

A column size 400mmÃ—400mm with an unsupported length 3750mm subjected to a load of 900 kN . Evaluate the steel reinforcement requirement . If grade of concrete M20 and grade of steel Fe500.

@Santanu Baruah. . . .Though you have not mentioned all required condition, but considering Both end Fixed Column and only Unfactored Axial Load of 900KN then required Longitudinal Steel will be

12 Nos. – 12mm Dia. Bars. [1st Choice]

or

4 Nos. – 16mm Dia. [2nd Choice]

4 Nos. – 12mm Dia.

is there a 5mm diameter bar?

Thank you no one can explain this in such a easy way.. It helps me a lot..

Thanks for all your Appreciation, Please Do share the link among yur friends so that they may also find it. Yes, there is 5mm Dia. Bar available, generally in coils, But the modern practice is to use 8mm Dia Lateral Ties at Minimum.

Very easy and Convenient design steps…Keep up the good work sir !

Very easy way of Column Design…Please Keep up the good works sir !

great post…….. to be honest it was the easiest way to understand the concept of designing a column but could you explain in more detail about influence area and the whole procedure by a practical example……thanks regards…………….

how to design rcc column for tensile force with biaaxial bending