Shear strengthening of RC T-section beams with low concrete using NSM CFRP laminates

Abstract

The effectiveness of NSM technique with CFRP laminates for the shear strengthening of T-section RC beams of low strength concrete was assessed. Five NSM shear strengthening configurations (three CFRP orientations and two levels of CFRP percentage) were applied in RC beams with a steel stirrups percentage of 0.10% and of 0.17%. The results showed that: NSM technique is still effective in beams of low strength concrete; inclined are more effective than vertical laminates; the beam’s shear resistance increases with the CFRP percentage; the NSM strengthening effectiveness decreases with the increase of the steel stirrups percentage. Using available experimental results obtained with the same test set-up but using beams of higher strength concrete it can be concluded that as minimum is the concrete strength as less effective is the NSM technique. In general, the formulation proposed by Nanni et al. provided safe and acceptable estimates for the contribution of the NSM shear strengthening systems (the predicted values of the CFRP contribution for the shear resistance were 75% of the results registered experimentally).