The effect of length and inclination of carbon fiber reinforced polymer laminates on shear capacity of near-surface mounted retrofitted reinforced concrete beams

This study undertakes a comprehensive investigation of the shear behavior of reinforced concrete (RC) beams strengthened by near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminates. Different strengthening configurations were employed by varying the length and inclination angle of the CFRP laminates. Results indicated that NSM-CFRP strengthening increased the load-carrying capacity, ductility, stiffness, and toughness from 8% to 41%, 9% to 78%, 24% to 159%, and 22% to 254%, respectively. Results also confirmed that as the CFRP laminate length decreases, the efficacy of the strengthening process increases, where the load-carrying capacity, ductility, stiffness, and toughness improved from 8% to 19%, 10% to 21%, 8% to 68%, and 26% to 119%, respectively. Also, the comparative results revealed that specimens strengthened with 45 -inclined CFRP laminates versus those strengthened with vertical laminates had higher load-carrying capacity (2%-10%), ductility (1%-35%), stiffness (24%-40%), and toughness (13%-32%). Two analytical formulations to predict the contribution of the possible distinct NSMCFRP shear strengthening configurations for the shear resistance of RC beams were considered. Results indicated an agreement between the experimental and the analytical results for both formulas, where the average values for the safety factor, k, k 1/4 Vana t =Vexp t were 0.80 and 0.73, with corresponding values of standard deviation of 0.195 and 0.125, respectively.

Automated summary

The study showed that NSM-CFRP strengthening significantly improves the load-carrying capacity, ductility, stiffness, and toughness of RC beams. Shorter CFRP laminate lengths result in better strengthening effectiveness. Beams strengthened with 45° inclined CFRP laminates outperform those strengthened with vertical laminates.