NSM shear strengthening technique with CFRP laminates applied in high T cross section RC beams

Abstract

The effectiveness of the Near Surface Mounted (NSM) technique with Carbon Fiber Reinforced Polymer (CFRP) laminates for the shear strengthening of relatively high T cross section (h = 600 mm) Reinforced Concrete (RC) beams was assessed by experimental research. Two inclinations of the laminates were tested (52° and 90°) and, for each one, two percentages of CFRP were adopted. The RC beams shear strengthened with NSM laminates had a percentage of steel stirrups of 0.09%. The experimental results showed that NSM shear strengthening technique with CFRP laminates is very effective in RC beams of relatively high cross section height, not only in terms of increasing the load carrying capacity of the beams, but also in assuring higher mobilization of the tensile capacity of the CFRP. Furthermore, inclined laminates were more effective than vertical laminates and the shear capacity of the beams increased with the percentage of laminates. Taking into account available experimental results obtained with the same test setup, but using RC beams of lower depth of T cross section (h = 400 mm), it can be concluded that the effectiveness of the NSM technique with CFRP laminates increase with the increase of the depth of the cross section. The formulations provided by Nanni et al. (2004) and Dias and Barros (2013) for the NSM shear strengthening technique predicted a CFRP contribution around 51% and 67%, respectively, of the experimentally registered values.