Experimental Study on Flexural Performance of SFCB-Reinforced ECC-Concrete Composite Beams

Engineered Cementitious Composite (ECC) exhibits superior tensile strain-hardening behavior and enhanced crack control due to its distinctive multiple cracking characteristic. In contrast, Steel-Glass Fiber Reinforced Polymer (GFRP) Composite Bars (SFCBs) combine the ductility of steel with the corrosion resistance of GFRP. To investigate the synergistic mechanisms for optimizing the performance of concrete structures, this study designed eight SFCB-reinforced ECC-concrete composite beams. Four-point bending tests were conducted to examine the influence of the ECC replacement height in the tension zone (hE/h = 0%, 16.67%, 33.33%, 50%) and the steel ratio in the bottom longitudinal reinforcement (As/Ab = 0%, 9%, 25%, 49%, 100%) on the flexural performance. The experimental results demonstrated the following: (1) Increasing the ECC replacement significantly improved both the ultimate bending capacity and ductility, while exerting a limited effect on flexural stiffness. Specifically, when increased from 0% to 50%, the ultimate bending strength and ductility index increased by 4.79% and 8.09%, respectively. (2) The steel ratio predominantly governed the yield behavior and crack development. Higher steel ratios resulted in increased flexural stiffness prior to yield, higher yield moments, improved ductility at failure, and superior crack control capability before yielding. (3) The synergistic mechanisms were identified: the ECC layer optimizes crack control by distributing crack-induced strains through multiple cracking, while the steel ratio within the SFCB regulates the ductile response. The findings of this study provide valuable theoretical guidance for enhancing the capacity and ductility of building structures.