Design of Beam (Steps and Example)

Steps

Step I: Assume suitable value of b/d ratio. [ 0.3 < b/d <0.7 ]

Step II : Assume suitable Value of “d” based on deflection criteria.

[l_eff /15 ] < d <[ l_eff /10]

Applying deflection Criteria

Here,

and k₂ = k₃ =k₄ = 1

k₂ = 1 because percentage of tension reinforcement is not known, k₃ =1 because Section is singly reinforcement and k₄ = 1 because of rectangular section.

Based on above two condition assume “d” and calculate “b” and “D”. Since l_eff is not known, l_clear or l_c/c can be taken for initial calculation.

Step III: Calculate dead load and design bending Moment.

Step IV : Calculate “d_req” required for balanced section.

BMu = MoR,lim

BMu = Q,lim bd²

Note : This “d” calculated must be less than “d” assumed initially if not redesign.

Step V: Since section provided is under reinforcement, Compute Ast.

Step VI: Ast Calculated must be satisfy permissible limits.

Step VII: Check for side Reinforcemnt

Step VIII : Check Deflection.

Design Example :

Q. Design a simply supported singly reinforced beam of rectangular section spanning over clear span of 11m, & resisting on 400 mm thick wall on one side & 600 mm thick wall on other side. It is subjected to superimposed Live load of 300 KN/m. Use M30, Fe500 grade of concrete and grade of steel respectively. Consider severe exposer condition.

By using Graphs also check for deflection.