Flexural behavior and crack width predictions of RC beams with different pre-damage degrees strengthened by UHPC

UHPC provides a new solution for reinforcing damaged RC bridge decks due to its ultra-high strength and durability. However, the crack performance of RC beams with varying damage degrees reinforced by UHPC layers employing different parameters remains unclear, and there is a lack of predictive formulas for estimating the maximum crack width. This paper aims to elucidate the flexural behaviors (e.g., Flexural cracking behavior, ultimate capacity, and crack width) of RC beams with different pre-damage degrees strengthened by UHPC. The influence of main design parameters such as the pre-damage degrees of RC beams, the UHPC layer thickness, and the reinforcement ratio on crack behavior was investigated. The experimental results show that the cracking load and ultimate load of pre-damaged RC beams strengthened by the UHPC layer have been significantly improved. Reducing the pre-damage degree of RC beams and increasing the reinforcement ratio of the UHPC layer could enhance the strengthened beams' cracking load and ultimate load. However, as the thickness of the UHPC layer increases, the ultimate load increases, but the cracking load decreases. Based on the experimental results, a formula for the maximum crack width on the UHPC surface of the UHPC-RC composite beam was proposed. Experimental results and related literature verify the applicability of the formula, and the formula has good accuracy. • Eight UHPC-RC composite beams and one RC beam are investigated by bending tests. • The influence of main design parameters such as pre-damage degrees of RC beams, thickness of UHPC layer, and reinforcement ratio on crack behavior is investigated. • A new formula is proposed to predict the maximum crack width in UHPC-RC composite beams. • The applicability of the proposed formula is verified.