Torsional behaviour of high strength concrete beams with spiral reinforcement

ABSTRACT The torsional behaviour of high-strength concrete beams that are transversely reinforced with continuous spiral reinforcement is experimentally investigated in this research. Seventeen specimens are divided into four groups according to their concrete strength: 25, 50, 60, and 70 MPa. Two types of transverse reinforcement, including closed and spiral stirrups, are used at a transverse spacing of 75 and 125 mm for each group. Test results are compared to the analytical values predicted using the ACI equation. Test results have shown an enhancement in the ultimate torsional capacity for the specimens made with high strength concrete compared to those made using normal strength concrete. The enhancement percentage ranges from 1.4% to 46.3%. In addition, results have shown an enhancement in the ultimate torsional capacity for specimens reinforced with spiral reinforcement compared to specimens made with conventional closed stirrups. The enhancement percentage varies from 8.3% to 34.6%. The study concluded that utilising continuous spiral reinforcement would result in higher ultimate torsional capacity than traditional closed stirrups for the same strength of concrete and that the torsion equations of ACI-318 M-19 are applicable and conservative for high strength concrete with a continuous spiral reinforcement.