Generalised approach for designing RC beams

摘要

As per IS 456 : 2000 and other codes, a reinforced concrete (RC) beam may be designed as a singly-reinforced or a doubly-reinforced section, depending on the bending moment. If it is designed as a singly-reinforced section, the actual reinforcement, which is provided on the compression face for hanging stirrups, is ignored in the design. If the beam is designed as a doubly-reinforced section, the actual reinforcement available on the compression face can be found to be more than the design reinforcement. In fact, the provided reinforcement may modify the assumed strain diagram (and hence the stress diagram). As a result, the actual moment resisting capacity of the beam may be different (usually morel than the moment for which the section is designed. This paper presents a generalised approach and evolves the necessary equations and tables for calculating the moment-carrying capacity of an RC beam section for a combination of available tension and compression reinforcements. The derived tables can also be used for selecting a suitable pair of reinforcements (tension and com press ion) for resisting a given design bending moment so that both the reinforcements are utilised to their maximum possible extent.