Design Procedure for Rectangular Beam
Steps for designing rectangular beams are given below:
1) Calculate the loads acting on the beam.
2) Calculate the maximum factored load by using the formula:
Wu = 1.2WD + 1.6WL
3) Width/Breadth of beam is taken
1/15 for smaller beams
1/20 for larger beams
According to code provision:
Breadth of beam = b ≥ span/30
4) Calculate Bending moment according to beam type & load
pattern (MU).
B.M of cantilever beam with point load = W*L
B.M of Cantilever beam with U.D.L = (W*L*L)/2
B.M of simply supported beam with point load = (W*L)/4
B.M of simply supported beam with U.D.L = (W*L*L)/8
For more understanding on how these formulas are derived, check out
this document.
5) Minimum Depth = dmin = √MU/(0.205 * fc’ * b )
Select the dimensions so that the Overall height is greater than or
equal to dmin.
h = dmin + 60mm(2.5”) for single layer of steel
h = dmin + 75mm(3”) for more layers of steel (double reinforcement).
6) Calculate Area of Steel (AS) from either of the following methods:
i) Direct Method:
In this method, find w = 0.85*(fc’/fy) & R = MU/bd2
Then, steel ratio = ρ = w[1-√1 - 2.614R/fc’]
Steel area = AS = ρbd
ii) Trial Method:
Assume a reasonable value of depth of rectangular stress block “a”. A
value close to d/4 or d/3 may be selected at the start. Calculate the
area of steel AS with the assumed value of ‘a’.
Steps for designing rectangular beams are given below:
1) Calculate the loads acting on the beam.
2) Calculate the maximum factored load by using the formula:
Wu = 1.2WD + 1.6WL
3) Width/Breadth of beam is taken
1/15 for smaller beams
1/20 for larger beams
According to code provision:
Breadth of beam = b ≥ span/30
4) Calculate Bending moment according to beam type & load
pattern (MU).
B.M of cantilever beam with point load = W*L
B.M of Cantilever beam with U.D.L = (W*L*L)/2
B.M of simply supported beam with point load = (W*L)/4
B.M of simply supported beam with U.D.L = (W*L*L)/8
For more understanding on how these formulas are derived, check out
this document.
5) Minimum Depth = dmin = √MU/(0.205 * fc’ * b )
Select the dimensions so that the Overall height is greater than or
equal to dmin.
h = dmin + 60mm(2.5”) for single layer of steel
h = dmin + 75mm(3”) for more layers of steel (double reinforcement).
6) Calculate Area of Steel (AS) from either of the following methods:
i) Direct Method:
In this method, find w = 0.85*(fc’/fy) & R = MU/bd2
Then, steel ratio = ρ = w[1-√1 - 2.614R/fc’]
Steel area = AS = ρbd
ii) Trial Method:
Assume a reasonable value of depth of rectangular stress block “a”. A
value close to d/4 or d/3 may be selected at the start. Calculate the
area of steel AS with the assumed value of ‘a’.
