Steps for design of cantilever beam

 

Steps for design of cantilever beam

1.     Basic data

Enter the values of b, clear span(L), fck, fy, clear cover, superimposed load, Overall depth (D), dia. Of bar() and calculate effective depth provided,

dprov = D – clear cover -

2

 

2.     Effective span

Leff = min. of { L + 𝑏𝑠 and L + 𝑑}

2                     2

 

 

3.     Factored SF & BM

Self wt. of beam = b*D*unit wt. of concrete Factored load, wu = 1.5*(S.D.L + self wt.)


Factored BM, Mu


= 𝑤𝑢𝐿2𝑒𝑓𝑓

2


Factored SF,     Vu = wu * Leff

 

 


 

4.     Design parameters

Find   𝑋𝑢𝑚𝑎𝑥=           700                  &

𝑑          1100+0.87𝑓𝑦

 

Qlim = 0.36*𝑋𝑢𝑚𝑎𝑥 (1 0.42 𝑋𝑢𝑚𝑎𝑥) 𝑓𝑐𝑘

𝑑                                           𝑑

·        Find the effective depth required to satisfy the deflection criteria as follows:

𝐿 = 7 * M.F        ((For cantilever beam as per IS 456-2000, pg-37)

𝑑

Find M.F from graph given on pg-38 of IS 456-2000)

d =     𝑳

𝟕 𝑴.𝑭

·        Find effective depth required for balanced section as follows:



𝑑𝑏𝑎𝑙


=       𝑀𝑢

𝑄𝑙𝑖𝑚  𝑏


Check:

Effective depth provided (dprov) should be more than the depth required to satisfy the deflection criteria as well as depth required for balanced section. If not, increase the overall depth.

·        Calculate percentage of R/F required:


𝑓𝑐𝑘                         4.6 𝑀𝑢


𝑝𝑡𝑟𝑒𝑞 = 50


𝑓𝑦  {1 √1 𝑓𝑐𝑘 𝑏 𝑑2}


 

 


Ast,req  = ptbd

100

 

A             = N*pi*φ2

 


 

 

and check A       <A


st,provided                       4

5)    Design of shear R/F


st,req


st,provided


Same as singly reinforced beams (Check the video in the channel below)

 

 

6)    Check for deflection

As per IS 456-2000, to satisfy the deflection critieria,

·        (L/d)actual < (L/d)permissible

 

·        (L/d)permissible = 7 * M.F (For Cantilever beams as per IS 456- 2000, pg-37)

 

And M.F from graph on pg-38 of IS 456-2000.

7)    Check for development length

Same as singly reinforced beams (Check the video in the channel below)



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