Beam Design to BS 8110

Singly Reinforced Section design

Beam design can be done for different codes depending on specific requirements. Before designing a beam, first, we need to find the bending moments and shear forces of the beam section through an analysis.

BS 8110 part 01 is one of the most commonly used standards, and the method expressed in the code can be understood very easily compared guides given for the design of other elements.

Design example

Design Data

Bending Moment    = 250 kNm

Shear Force                = 200 kN

Beam width                = 225 mm

Beam height               = 600 mm

Grade of the concrete = 25 N/mm2

Strength of the steel    = 460 N/mm2

Cover to R/F               = 30 mm

Shear links diameter   = 10 mm

No redistribution of the moment is assumed.

Calculations

effective depth      = 600-30-10-20/2

                                    = 550 mm

                     K            = M/bd²fcu

                                    = 250×10⁶/(225×550²x25)

                                    = 0.147

                     K            < K’ = 0.156

Hence, the section is singly reinforced.

                     Z             = d[0.5+{0.25-K/0.9}^1/2]

                                    = 550[0.5+{0.25-0.147/0.9}^1/2]

                                    = 436.995 mm

                     As          = M / (0.95fyZ)

                                    = 250×10⁶ / (0.95x460x436.995)

                                    = 1309 mm²

Provide three 25 mm bars.

The properly designed beam could fail due to many reasons. Article 6 causes of beam failures could be read for more information.