Shear failure in conventional reinforced concrete (R/C) beams is characterized by pronounced brittleness, limited energy dissipation capacity, and a high propensity for catastrophic collapse due to the absence of discernible warning signs. This study investigates the use of high-ductility fiber-reinforced cementitious composites (Engineered Cementitious Composites, ECC) to enhance the shear performance of concrete beams. An experimental program was conducted on both R/C and reinforced ECC (R/ECC) beams subjected to shear, complemented by a novel numerical approach to quantify the contributions of arch action ( V a ) and beam action ( V b ) to shear resistance. The findings reveal a strong positive correlation between the efficiency of arch action and overall shear performance, including shear carrying capacity, deformation capacity, and ductility. Building on these insights, an optimized design strategy incorporating partial ECC replacement and pre-defined voids is proposed, illustrating the potential of a mechanism-driven approach to achieve superior shear behavior in structural elements. • Quantifies arch and beam actions in R/C and R/ECC beams via numerical analysis. • R/ECC beams preserve intact compression zones and significantly enhance arch action. • Partial ECC replacement can boost shear carrying capacity by up to 105.7%. • Arch action dominates shear resistance when shear span-to-depth ratio is small. • Enhancing arch action via voids offers an effective shear-strengthening strategy.
Gu et al. (2026) studied this question.