Torsional strengthening of concrete members using near-surface mounted CFRP composites

To increase the strength of concrete members, numerous research studies on flexure and shear have been reported using carbon fibre-reinforced polymer (CFRP) with the near-surface mounted (NSM) strengthening technology, as it is considered a promising technology. However, to date research on torsional strengthening has been provided only for the externally-bonded reinforcement technique (EBR) and no studies have been conducted on NSM strengthening technology. In this paper, reinforced concrete (RC) beams with CFRP are considered and ATENA software is used to build a 3-D model of the beams and to analyse the beam structure. Finite element and experimental results of the control beam and beams strengthened for torsion with CFRP sheets using the EBR technique are compared. Further computer analysis of beams strengthened with CFRP laminate using the NSM strengthening technology is achieved by considering many parameters. The type of the adhesive, the method of strengthening, and the spacing between the grooves were examined. The performances of the beams and the ultimate strengths of the control and beams strengthened using the EBR technique were predicted with high accuracy by the models employed. According to the results for the beams strengthened using the NSM technique, the overall torsional behaviour of the beams with CFRP was improved by different percentages and the beams became stronger.