Displacement Ductility of Helically Confined HSC Beams

This paper presents an experimental investigation of the effect of helix pitch and helix diameter on beam behaviour through testing 10 helically confined beams. Two groups of beams had exactly the same geometry and reinforcement; with the only differences being the helices diameter and pitch. 8 mm helix was used in the first group of beams and 12 mm bars in the second group. The helix pitches varied between 25 mm and 160 mm. Beams' cross section was 200 x 300 mm, with a length of 4 m subjected to four point loading. The main results indicate that the helical effectiveness is neglected when the helical pitch is 160 mm (helix diameter) and the displacement ductility index increases as the helical pitch decreases. Finally, there is a considerable release of strain energy responsible for spalling off the cover.