Flexural strength and deformability design of reinforced concrete beams

Abstract

In the flexural design of reinforced concrete (RC) beams, the strength and deformability, which are interrelated, need to be considered simultaneously. However, in current design codes, design of strength is separated with deformability, and evaluation of deformability is independent of some key parameters, like concrete strength, steel yield strength and confinement content. Hence, provisions in current design codes may not provide sufficient deformability for beams, especially when high-strength concrete (HSC) and/or high-strength steel (HSS) are used. In this paper, influences of key factors, including the degree of reinforcement, concrete strength, steel yield strength, compression steel ratio, and confining pressure, are studied based on a theoretical method. An empirical formula for direct evaluation of deformability is proposed. Interrelation between the strength and deformability are plotted in charts. Based on the empirical formula and charts, a new method of beam design called "concurrent flexural strength and deformability design" that would allow both strength and deformability requirements to be considered simultaneously is developed. The method provides engineers with flexibility of using high-strength concrete, adding compression steel or adding confinement to increase deformability of RC beams.