Effects of tensile reinforcement ratio and compressive strength on the behaviour of over-reinforced helically confined HSC beams

The technology of high strength concrete has improved over the last decade. High strength concrete (HSC) is more brittle than normal strength concrete. The brittleness increases with the use of over-reinforced section, which fails suddenly without warning. Use of over reinforced sections is restricted in codes of practice of concrete design. This paper presents an experimental study of the behaviour of five HSC beams confined with helical reinforcement. Concrete compressive strength in the range 72–95 MPa and tensile reinforcement ratio in the range 5.24–7.86% were used. The main results indicate that as the concrete compressive strength increases the displacement ductility index decreases and the load at spalling-off the concrete cover increases. Also, the displacement ductility index increases as the longitudinal reinforcement ratio increases and the load at spalling-off the concrete cover decreases.