Flexural and shear behaviors of reinforced ultrahigh toughness cementitious composite beams without web reinforcement under concentrated load

Ultrahigh toughness cementitious composite (UHTCC) behaves strain-hardening and multiple-cracking when subjected to tensile load. The current work investigates both bending and shear performances of steel reinforced UHTCC (RUHTCC) beams through the bending test under concentrated load. The failure mode was designed from flexure to flexure-shear to shear through varying reinforcement ratio in beam. The experimental results showed that for flexural behavior, RUHTCC beams presented high load-carrying capacity, deformation ability and numerous fine cracks around mid-span region in comparison with ordinary reinforced concrete (RC) beam. Based on the internal force equilibrium, the theoretical equation for determining the moment of inertia of fully cracked section of RUHTCC beam is proposed, and the predicted maximum deflection at service load according to proposed equation based on bilinear tensile and compressive constitutive models agrees well with the tested value. For shear behavior, RUHTCC beam exhibited shear strength about 1.91 times that of RC control beam and a large reserve of shear bearing capacity after the shear cracking due to the diagonal multiple-cracking pattern and the stable crack development. And for RUHTCC beam with reinforcement ratio of 2.28% failing in flexure-shear, a large deformation comparable to that of RC beam with 0.67% reinforcement ratio was observed.