EXPERIMENTAL INVESTIGATION OF FLEXURAL PERFORMANCE OF T-SHAPED HYBRID CONCRETE BEAMS RETROFITTED WITH NSM TECHNIQUE USING GFRP BARS

In this research, thirteen T-shaped hybrid concrete beams were designed to investigate their flexural behavior. Flanges of all beams were cast by 106 N/mm2 fcu of self-compacting high-strength concrete (SC-HSC), while the webs were made by 45 N/mm2 fcu of normal-strength concrete (NSC). One beam was loaded up to failure as a control beam (CB), and the other beams were divided into two groups; the first group consisted of six beams preloaded by 45% of CB's ultimate load (Pu), and the other group of beams subjected to 85% of CB's Pu. Beams were retrofitted along the entire clear span using various numbers and placements of glass fiber-reinforced polymer (GFRP) bars mounted near the bottoms and side(s) surfaces. However, tests resulted in a notable enhancement ranging from 35% to 101% of retrofitted beams. At the same time, the maximum deflections of both groups witnessed a range from 21.9 mm to 34.9 mm beside CB's ultimate deflection (33.8 mm); in addition, ductility ratio, toughness, and stiffness values varied between (55.89% and 73.8% reduction), (15.95% decrement and 31.96% increment), and (2.36% and 47.83% reduction), respectively. Furthermore, the failure mode was mainly GFRP-Epoxy debonding