Parametric Study of the Physical Responses of NSM CFRP-Strengthened RC T-Beams in the Negative Moment Region

This study presented a comprehensive finite element (FE) investigation into the flexural behavior of RC T-beams strengthened in the negative moment region using near-surface mounted (NSM) carbon-fiber-reinforced polymers (CFRP) rods. A three-dimensional nonlinear FE model was developed and validated against experimental data, achieving close agreement with normalized mean square error values as low as 0.006 and experimental-to-numerical ratios ranging from 0.95 to 1.04. The validated model was then employed to conduct a systematic parametric analysis considering CFRP rod diameter, concrete compressive strength, longitudinal reinforcement ratio, and FRP material type. The results showed that increasing CFRP diameter from 6 to 10 mm enhanced ultimate load by up to 47.51% and improved stiffness by 1.48 times. Higher concrete compressive strength contributed to stiffness gains exceeding 50.00%, although this improvement was accompanied by reductions in ductility. Beams with reinforcement ratios up to 2.90% achieved peak loads of 309.61 kN, but ductility declined. Comparison among FRP materials indicated that CFRP and AFRP offered superior strength and stiffness, whereas BFRP provided a more balanced combination of strength and deformation capacity.