EXPERIMENTAL STUDY ON PURE TORSION AND BENDING-TORSION PERFORMANCE OF T-SECTION STEEL REINFORCED CONCRETE BEAMS

In order to study the mechanical properties of T-section steel reinforced concrete beams under pure torsion and bending torsion, 12 pure torsion and bending torsion tests of T-section steel reinforced concrete beams were designed and implemented by considering their flange width, steel ratio, stirrup ratio, flange longitudinal reinforcement diameter, and bending-torsion ratio as variation parameters. The failure process of specimens was observed, and the important characteristic parameters were obtained, such as torque-torsion ratio curve, cracking torque, and ultimate torque of the specimens. The influence of different variation parameters on the torsional performance of T-section steel reinforced concrete beam under pure torsion and bending torsion was analyzed in depth, and the torsional failure mechanism was revealed. The results show that the failure modes of the T-section beam and rectangular-section beam are basically the same. The reinforced concrete beam presents brittle failure, and the steel reinforced concrete beam presents ductile failure. There is a mutual constraint between the flange, steel, and concrete of the T-section specimen, and the flange and steel greatly enhance the torsional strength and ductility of the specimen. The optimum aspect ratio of specimen flange is 2.33; with the increase of steel ratio, the torsional strength and ductility of the specimens increase, with an average increase of 30.99% and 101.14%, respectively. The ultimate torque of the specimen increases with the increase of the bending-torsion ratio, with an average increase of 7.86%. Based on the experimental analysis, the calculation formulas for cracking torque and ultimate torque of T-section steel reinforced concrete beams are proposed. The calculated results are in a good agreement with the experimental results.