vol22no1pa2

In this work, an experimental study has been conducted to investigate the behavior of high strength self-compacted concrete hollow beams under pure torsion. In this work, the beams were implemented and tested under pure torsion load. A total of six beams were tested. All beams were of the same cross section, the same length, the same concrete mixture and quality control. All beams were of external dimensions (300x300mm) and the hollow dimensions (180 x180mm) and all the concrete beams have the same number of main reinforcement 4Ф12 at the top and 4Ф12 at the bottom, the main variable is the stirrups spacing to investigate the effect of stirrups amount on improving of hollow reinforced concrete beams resistance against torsional moments. The six beams were subjected to pure torsion by using fabricated test machine to enable the application of the mentioned pure torsion load. Experimental results showed that, many structural properties of the beams are improved, by decreasing the stirrups spacing. Highest improvement achieved for ultimate torsional moment (Tu) followed by cracking torsional moment (Tcr) and then by angle of twist (Ø) while the improvement of beam’s concrete strain (ε) came at last. The percentage of improvements of the mechanical properties of the beams due to decrease of the stirrups spacing according to the reference beam is: •For Tu ranges between (25.7-254.3) %. •For Tcr ranges between (25-200) %. •For Ø ranges between (23.3-76.0) %. •For ε (29.0-50.2) %. The considerable increase in Ø and ε before failure makes the increase of stirrups preferable for safe life and attaining attention.