Effect of CFRP Strengthening Configuration and Steel Fiber on the Torsional Performance of Deep Beams under Repeated Pure Torsion
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Abstract
This study aims to investigate the torsional behaviour of reinforced concrete deep beams enhanced with various CFRP configurations and steel fibres, subjected to repeated pure torsional loads. Five beams were constructed using normal-strength concrete. One specimen was internally reinforced with 1% steel fibres, while the others were externally strengthened with CFRP sheets in different configurations. The tested specimens included a control beam without strengthening, a beam with longitudinal CFRP sheets, a beam wrapped with CFRP strips, a beam with only steel fibres, and a combined beam utilizing both CFRP and steel fibres as a combined strengthening method. The experimental results demonstrated significant improvements in the ultimate torque capacity of all strengthened beams relative to the control specimen. The ultimate torque increased by 30.8% in the longitudinal CFRP specimen, 46.2% in the wrapped CFRP specimen, 37.7% in the steel fibre specimen, and 43.7% in the combined strengthening specimen. The wrapped CFRP configuration exhibited the greatest enhancement. Furthermore, all strengthened beams showed improved crack control, higher torsional stiffness, and enhanced ductility under repeated pure torsional loading.
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