Maximum Size of Concrete Slab, Beam and Column  Calculation Formula
In this Article today we will talk about the Maximum Size of Concrete Slab  Concrete Slab Thickness  Maximum Thickness of RCC Slab  Maximum Height of Concrete Column  Maximum Length of Concrete Beam  Standard Size of Beam  Column Dimensions  Concrete Column Sizing  Minimum Concrete Thickness
Maximum Span/Length of the Beam:
The maximum span & depth of a beam (cantilever / simply supported / continuous) are decided by deflection limits
These deflection limits are defined in terms of L/d ratio, where ‘L’ is the effective span & ‘d’ is the effective depth of the beam member.
According To Is Code On Clause 23.2.1 of IS: 456 (2000) pg. no. 37 The same provisions are stipulated for beam spans of up to 10 m.
Cantilever; Span/d <= 7
Simply supported; Span/d <= 20
Continuous; Span/d <=26
Greater than 10m
Simply supported < = 20×10/span
Continuous < = 26×10/span
Thus, depending on the length provided, the minimum allowable depth of the beam member can be calculated, and likewise the maximum allowable span can be calculated using the L/d ratio for a given depth of the beam member.
Note:
Effective Span: Usually the c/c span of the beam member is taken into account for further reference. See clause 22.2 of IS:456 (2000) pg. 34
Effective depth: d = D – (cover) (dia of bottom bar/2)
D = effective depth
D = overall depth
Standard Size of Beam:
In a residential building it is 9 ʺ × 12 ʺ or 225 mm × 300 mm standard size according to (IS codes). The minimum RCC beam size should not be less than 9 ʺ × 9 ʺ or 225mm × 225mm with the addition of a 125mm rcc slab thickness. Maximum Height of Concrete Column
Maximum Thickness/Size of Concrete Slab:
Maximum Size of Concrete Slab:
tandards such as ACI 318 specify the minimum thickness of the slab based on the length of the slab. Column Dimensions
 Simply Supported Slab = L / 20
 One End Continuous Slab = L / 24
 Both End Continuous Slab = L / 28
 Cantiliver = L / 10
However, in other criteria, they do not directly specify the minimum slab thickness.
MINIMUM THICKNESS OF THE SLAB AS PER IS 456:2000  
Simply supports slabs spanning in one direction  L/30 
Simply supports slabs spanning in Two directions (Twoway slab)  L/35 
Continuous slabs spanning in one direction  L/35 
Continuous slabs spanning in Two direction  L/40 
Cantilever slabs  L/12 
Minimum Thickness of Concrete Slab:
Concrete is generally applied with a thickness of 2 inches or more, but the thicker it is, the stronger the slab will be. Four (150mm) inches is more common for a slab
Concrete Column Sizing or Column Dimensions
Maximum Allowable Height of a Column without any Brace or Tie:
Columns can build as long column fails by buckling.
So if the slenderness ratio of the rcc column is greater than 12, that the column is classified as a long column.
Slenderness ratio=L(eff)/R(min)
L (efff) has to be determined as per IS 456:2000
R (min) = ( I(min) /Area of crosssection )^{1/2}
But simply it can be understood as if column size is of 250X 250 mm then as per slenderness ratio limit if 12
Therefore,
Slenderness ratio = Length /shorter dimension
i.e., 12= length/250
i.e., Length= 12 x 250=3000 mm
So if you make a column of size 250mm x 250mm it should not exceeds the height of 3m. if you need to build beyond it. It needs tie beams Minimum Concrete Thickness
Stanadard Size of Column:
The size of the columns depends on the total load on the columns. The minimum column size should not be less than 9 “x 9”. 9 ”x 9” columns are to be used for a singlestory concrete grade M15 (1: 2: 4) structure (cement: sand: aggregate).
Maximum Column Size for Different Stories:
S.NO 
NO. OF STORY 
SIZE 
1 
12 
230mm x 230mm 9” x 9” 
2 
13 
300mm x 300mm 12”x12” 
3 
110 
750mm x 750mm 30” x 30” 
4 
120  
17 
800mm x 800mm 32” x 32”  
815 
600mm x 600mm 24” x 24”  
1620 
450mm x450mm 18” x 18”  
5 
130  
110 
850mm x 850mm 34” x 34”  
1120 
650mm x 650mm 26” x 26”  
2030 
475mm x475mm 19” x 19” 
NOTE: These are the standard RCC column sizes, but it will increase or decrease with respect to the load.
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FAQs:
Conclusion:
Full article on Maximum Size of Concrete Slab  Concrete Slab Thickness  Maximum Thickness of RCC Slab  Maximum Height of Concrete Column  Maximum Length of Concrete Beam  Standard Size of Beam  Column Dimensions  Concrete Column Sizing  Minimum Concrete Thickness. Thank you for the full reading of this article in “The Civil Engineering” platform in English. If you find this post helpful, then help others by sharing it on social media. If any formula of BBS is missing from this article please tell me in comments.
6 Comments
I find it very interesting and helpful to learn the basic knowledge and also in learning new things everyday
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Thank you
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Sir mere slab 9 inch ho Gaya hai Kya karu
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