Effects of confinement on flexural strength and ductility design of HS concrete beams

High-strength concrete is relatively brittle and its use in a reinforced concrete member might result in unacceptably low flexural ductility. One way of improving ductility is to provide confinement. However, in the case of beam design the effects of confinement are generally not considered due mainly to the lack of a suitable design method. In order to develop a design method for improving the flexural ductility of highstrength concrete members through the provision of confinement, the effects of confinement on the flexural behaviour of reinforced concrete beams have been evaluated in this study by complete moment-curvature analysis of beam sections with and without confinement provided. It was found that the provision of confinement significantly increases the ultimate concrete strain, balanced steel ratio and flexural ductility.

Furthermore, design formulae for the flexural strength and ductility design of high-strength concrete beams with the effects of confinement
taken into account have been developed.

A. K. H. Kwan
F. T. K. Au
S. L. Chau
Department of Civil Engineering, The University of Hong Kong, Hong Kong