Flexural strength and ductility of reinforced normal- and high-strength concrete beams

Abstract

A number of singly reinforced concrete beams made of normal- and high-strength concretes were tested under monotonically increasing loads to study their flexural behaviour and to compare the flexural ductility of normal- and high-strength concrete beams. The flexural strength results verified that British Standard BS 8110, after modification as per the recommendation of The Concrete Society Technical Report 49, is reasonably accurate for application to high-strength concrete beams. On the other hand, the flexural ductility results revealed that the major structural parameters determining the ductility of singly reinforced beams are: (1) for given materials, the tension steel ratio; and (2) in more general cases, the tension steel to balanced steel ratio and the concrete grade. Based on the available test results, a simple formula for predicting the ductility of normal- and high-strength concrete beams is developed. Lastly, in order to avoid brittle failure, it is proposed to set a maximum limit to the tension steel to balanced steel ratio, whose values at different concrete strengths are given in the paper.