EXPERIMENTAL AND ANALYTICAL STUDY ON BEHAVIOUR OF CFRP-STRENGTHENED HSC BEAMS WITH MINIMUM REINFORCEMENT UNDER PURE TORSION

Experimental investigation was conducted to study the pure torsional behaviour of highstrengthconcrete (HSC) beams strengthened with carbon-fibre-reinforced-polymers (CFRP) havingminimum torsional reinforcement. A total of six beams were tested. Two beams without CFRP wereassigned as control beams and the rest were strengthened using CFRP sheets. In this study, differentwrap configurations, the effect of different numbers of CFRP plies, and the influence of anchors inU-wrapped test beams considered as variables were investigated. Investigation into ductility usingtwo different concepts showed enhancement in the behaviour of strengthened beams with CFRP.The ductility of the beam strengthened with two complete CFRP layers was fifty percent higher thanthat of the control beams. The beam strengthened using this scheme showed a 75% increase intorsional capacity compared to the control beam, which was not strengthened. The experimentalresults were compared with the results from three analytical methods. The ultimate torsionalstrength resulting from one of the three methods, which was based upon synthesis of an analyticalmethod and average CFRP strains obtained from experiments, was in good agreement with theexperimental results.