Singly Reinforced Beams – BS 8110:1:1997 – Example 1

Question – A simply supported rectangular concrete beam of 7 m span carries a characteristic dead load (G_k), including self-weight of the beam, and imposed load (Q_k) of 7 kNm and 5 kNm respectively.

The beam dimensions are breadth b = 225 mm and effective depth d = 400 mm.

Assume f_cu = 30 N/mm² and f_y = 460 N/mm².

Calculate the area of reinforcement required.

Answer:                      Given             b = 225 mm,   d = 400 mm,   l = 7.00 m,  

G_k = 7.00 kNm,          Q_k = 5.00 kNm,

f_cu = 30 N/mm²,          f_y = 460 N/mm².

Ultimate load (w)                    =          1.4G_k + 1.6 Q_k

                                                   =          (1.4 x 7.00) + (1.6 x 5.00) kN/m

                                                   =          17.80 kN/m

Cross-sectional area of 01 no. 16 mm diameter bar = 201 mm²

                         Provide 4 nos. of 16 mm diameter bars resulting 804 mm².

Note: However, there are other limitations before considering the size and spacing of bars. Those factors will be discussed in another example.