Experiment study on reactive powder concrete beams using spirals reinforcement under torsion

Abstract

This paper investigates the torsional behavior of reactive powder concrete (RPC) beams using spiral reinforcement. The influences of parameters, including different spiral reinforcement configuration, spiral reinforcement ratio, and the steel fiber content on the torsional performance of the nine RPC beams, were investigated and discussed. The experimental results showed that the failure mode, ultimate torque, torsional stiffness, and energy dissipation of the RPC beams were not affected by longitudinal reinforcement alone, but it improved the ductility. Compared to commonly used stirrups, the locked spiral reinforcement exhibits more torsional ductility, stiffness, and ultimate torque of the RPC beams. But the torsional ductility, stiffness, and ultimate torque decreased when the spiral reinforcement was unlocked. The cracking torque and pre-cracking torsional stiffness of beams were less affected by the locking and unlocking of spiral reinforcement. Greater steel fiber content and spiral reinforcement ratio resulted in higher torsional ductility, torsional stiffness, energy dissipation and ultimate torque of the locked spiral reinforcement reinforced beams. The pre-yielding torsional stiffness and plastic dissipation capacity were strongly influenced by spiral reinforcement states and spiral reinforcement ratio. The pre-cracking torsional stiffness and energy dissipation of RPC beam were determined by the steel fiber content. Considering the torsional contribution of steel fiber and concrete tensile strength, a new formula for calculating the ultimate torque of RPC beam was proposed, and the calculated value was closer to the experimental value.