Enhancing shear performance in UHPC beams through strategic fiber and stirrup integration

This study pioneers a systematic experimental investigation into the combined effects of fiber volume and transverse reinforcement—both normal-strength steel (NSS) and high-strength steel (HSS)—on the shear performance of ultra-high-performance concrete (UHPC) beams, aiming to develop more efficient fiber–stirrup integration strategies. Twelve full-scale T-beams with varying fiber volumes (1 % and 2 %), transverse reinforcement types (NSS and HSS), transverse reinforcement ratios (0.4–0.7 %), and shear-span-to-depth ratios (1.7 and 2.7) were tested and evaluated using multiple performance indices, with results benchmarked against existing analytical models. Two alternative fiber–stirrup integration strategies were proposed and compared with the common practice of using 2 % fibers with or without stirrups: (1) reducing fiber content from 2 % (no stirrups) to 1 % with light NSS stirrups, and (2) replacing 2 % fiber beams with NSS stirrups by 1 % fiber beams with light HSS (MMFX) stirrups. Both alternatives maintained the shear resistance with 8–25 % lower costs, while also achieving finer crack control, smaller critical shear crack widths, and improved structural integrity. Collectively, these findings offer a pathway toward more economical and structurally resilient UHPC design practices, challenging conventional fiber–stirrup usage norms. • Shear resistance from fiber and HSS or NSS stirrup in UHPC beams. • 12 full-scale beams tested under varying fiber, stirrup, and a/d ratios. • Two proposed strategies matched shear capacity with up to 25 % lower cost. • Alternatives improved cracking, reduced CSC width, and enhanced integrity.