Experimental Investigation of the Shear Behavior of a Concrete Beam without Web Reinforcements Using External Vertical Prestressing Rebars

The shear performance of concrete beams is known to be an important mechanical feature; hence, enhanced shear resistance is critical for determining a beam's performance in terms of security and service life. This paper presents a study on the shear behavior of concrete beams without web reinforcement strengthened by external vertical prestressing rebars (EVPRs). Experimental data were obtained from seven test beams with varying influencing factors (stirrup ratioρ_sEP, arrangement spacings, prestressing forceF_p, and compressive stress degreeγ_pof the EVPRs) to determine their effects on the shear behavior. The results reveal that the EVPRs can significantly improve the shear capacity and ductility of concrete beams without web reinforcement. Furthermore, the failure mode is changed from brittle diagonal tension to relatively ductile shear compression, and the flexural cracks and shear cracks are more fully developed. The shear capacity becomes enhanced as theρ_sEPandγ_pare increased; vertical compressive stress provided by the EVPRs can reduce the principal tensile stress of the concrete structure to prevent the shear cracking and enhance the shear resistance of the concrete. Meanwhile, in the stage from the formation of the critical shear crack (CSC) to the shear failure, the EVPRs can be used as stirrups to share the shear load. It can be concluded that EVPRs can effectively improve the shear performance of concrete beams.

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