Ductility enhancement of RC beams strengthened with near surface mounted - SMA technique

Based on many studies carried out on strengthening RC beams and girders with the near surface mounted (NSM) technique with fibre reinforced polymer (FRP), ductility reduction has been observed. In this research, an advanced and promising technique for retrofitting previously designed RC beams known as the near-surface-mounted (NSM) method with shape-memory alloy (SMA) strips is proposed which can help overcome the shortcomings of the NSM-FRP technique. The ductility enhancement of NSM-SMA beams was studied numerically using 2D fibre element modelling via OpenSees software, and five types of SMA materials were used. Improving the RC beams' flexural behaviour using the NSM-SMA retrofitting technique was also discussed. Results showed that, for RC beams, the NSM-SMA technique enhanced the ductility to reach more than 90% in some of the NSM-SMA beams, and a reduction in the ductility of the NSM-CFRP beam was observed compared with the control beam.