Abstract: This paper presents an experimental investigation into the shear behavior of reinforced ultra-high toughness cementitious composite (UHTCC) beams through flexural tests under a point loading, where UHTCC shows tension strain-hardening and multiple cracking characteristics. The varied parameters include shear-span ratios of about 2.06, 3.08, and 4.11, and web reinforcement ratios of 0%, 0.25%, 0.37%, and 0.55%. The experimental results reveal that reinforced UHTCC (RUHTCC) beams have superior shear resistance compared with reinforced concrete (RC) beams and show stable crack propagation and multiple cracking behaviors in shear. The use of UHTCC as the matrix of beams can serve as a replacement for minimum web reinforcement. A small amount of stirrups used in RUHTCC slender beams results in a more ductile flexure-shear or even flexural failure. However, the use of stirrups in both short beams and RUHTCC slender beams brings little improvement in ultimate shear strength, and thus no shear synergy between UHTCC and stirrups is obtained. A tied-arch model and a truss model can be used to represent the shear mechanism of RUHTCC short and slender beams, respectively. UHTCC web subjected to tension can be considered as inclined tension web members in a truss model for RUHTCC slender beams.

Key words: Ultra-high toughness cementitious composite (UHTCC), Shear-span ratio, Stirrups, Shear strength, Diagonal crack, Shear mechanism

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