An experimental study was conducted on ten steel fiber reinforced concrete specimens with low longitudinal reinforcement ratio to investigate the torsional behavior under pure torsion. The crack patterns, cracking torque, ultimate torsional strength, and torsional ductility, were discussed. The major parameters were the ratio and type of adding steel fiber. The obtained results showed that the cracks width of end hooked steel fiber specimens were wider than the corrugated steel fibers specimens, the cracks width decrease with increase the steel fiber ratio, and the number of cracks of end hooked steel fiber specimens were less than the corrugated steel fibers specimens. In the specimens of mix steel fiber, the width and the number of cracks less and more than other specimens, respectively. The higher percentage of the steel fiber, gives greatest torsional resistance. However, with an increase in the percentage of steel fiber the workability decreases.

Twelve mixing steel fibers-reinforced high strength concrete beams were experimentally tested under pure torsion to investigating the concrete member torsional behavior. The first cracking torque, ultimate torsional resistance, crack patterns, effect of steel fiber ratio, effects of shape and size of hollow cross-section, and effect of stirrups reinforcement were discussed. The ratio of mixing steel fiber, different shape and size of hollow cross-section, and ratio of stirrups reinforcement were considers as major parameters. The results are shown that the width of cracks decreases and the cracks number increases with mixing steel fibers ratio increased. The first cracking torque and ultimate torsion load increased with decrease in the hollow cross-section area of high strength concrete members strengthened by steel fibers.