Evaluation of minimum flexural reinforcement in RC beams

An analytical study on the influence of beam size and strength of concrete for evaluation of minimum flexural reinforcement is reported. The empirical equations specified in the codes of practice may be re-evaluated and adjusted appropriately according to rational approach. The study of reinforced concrete beams using fracture mechanics of concrete with the help of fictitious crack model has been undertaken. The depth of beam was varied from 100 mm to 1500 mm and the strength of concrete was varied from 20 MPa to 70 MPa. The minimum flexural reinforcement in the beams has been established using the condition that the surface crack width at the tension face of the beam does not exceed the maximum crack mouth opening displacement. It has been noticed that the minimum flexural reinforcement increases with increase in the size of beam. As the strength of concrete increases, the minimum flexural reinforcement also increases. This has been attributed to the brittleness imparted by the structural size and material behaviour.