REINFORCED CONCRETE SLABS AND STEEL-CONCRETE COMPOSITE BEAMS UNDER PURE TORSION

摘要

The experimental results of reinforced concrete slabs and steel-concrete composite beams subjected to pure torsion are presented. The test series consisted of four slabs and four beams, and the major variables were the aspect ratio of cross section and the torsion reinforcements. All test slabs exhibited a typical skew-bending failure mode. The rotating-angle softened truss model (RA-STM) developed by Hsu underestimated the torsion strength of the test slabs. A new assumption was presented that the centerline of the shear flow coincided with the centroidal line of the equivalent compression stress block in the concrete struts, and torsion reinforcement ratios were redefined. The RA-STM using these proposals can predict not only the torsion strength but also the post-cracking behavior of the slabs accurately. Tests of the beams showed that only concrete flange contributed towards the torsion strength of composite beam. The contribution of joist can be neglected, but it plays a vital role in restraining concrete flanges from deforming longitudinally, which enhances the resistance of concrete flange. Additionally, several design formulas were discussed.