Torsional Behaviour of Strengthened Reinforced Concrete Beam on Two Sides by CFRP using NSM and EBROG Techniques

Abstract

Increased resistance of RC beams is one reason that CFRP materials are being used extensively. The high durability, electromagnetic neutrality, high strength and weight ratio, rapid execution with less work, ease of handling, dimensions and geometry are advantages of the use of CFRP. The utilization of the near-surface mounted (NSM) and externally bonding reinforcement on grooves (EBROG) techniques are becoming recognised as viable solutions to improving the strength of structures. These solutions are successful in effectively addressing and mitigating the problem of debonding. This paper presents four full-size RC box beams with hollow cross-sections measuring 400 mm x 400 mm and 3,000 mm in length (clear span from the face to face of supports was 2400 mm) that were selected in this study; one beam was used as control specimen whereas, the remaining three beams were partially strengthened on two sides by NSM-CFRP laminate strips and EBROG-CFRP sheet strips. The strengthening methods and the effect of spacing in NSM on the torsional behaviour have been discussed. The relationships between torsional moment and twisted angle, ductility of the beam specimens are investigated. The ultimate capacity torque of beam specimens strengthened by NSM and EBROG has resulted in improvements in the torque capacity of beams. Specifically, the enhancements have varied from 13% to 17% for NSM and 6% for EBROG compared to the reference beam.