A new perspective of ultimate flexural strength calculation model for reinforced rectangular section concrete beams

The ultimate flexural strength of reinforced concrete beams is often calculated based on an equivalent rectangle stress block in most countries, while the equivalent factors are obtained by statistical method. In this paper, the stress-strain curve of concrete recommended in GB 50010-2010 is adopted to acquire the equivalent factors, a new perspective of ultimate flexural strength calculation model for reinforced rectangular section concrete beams is proposed, by considering the varying of the equivalent factors with the strain of concrete at the extreme compression fiber. The performance of the proposed model is evaluated in comparison with that of the models in current codes using an experimental database of 312 reinforced rectangular section concrete beams failed in bending. It is found that the results from the proposed model are in good agreement with the experimental results. Besides, a characteristic reinforcement ratio is proposed to simplify the calculation model, which can be used as a reference for engineering application.