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In this study, ultrahigh-performance concrete (UHPC) was utilized in precast segmental beams to reduce the self-weight, shorten the construction time, and improve the performance and durability of bridges. Owing to the discontinuity in the joints, shear behavior plays a critical role in the overall structural performance of precast UHPC segmental beams (PUSBs). Therefore, four dry-jointed segmental specimens along with one monolithic specimen were designed and tested under a two-point concentrated load with various joint types, shear span-to-depth ratios (λ), and numbers of shear keys. Two types of shear failure modes were observed in the tests: shear compression failure of the web (λ = 1.44 and 2.56) and local shear failure of the flanges at the joint (λ = 3.67). The shear capacity, stiffness, and cracking load of the dry-jointed segmental specimens were lower than those of the monolithic specimen, and the single-keyed specimen exhibited better shear behavior than the three-keyed specimen. Increasing λ decreased the shear strength and stiffness of the segmental beams and considerably affected their failure modes and crack distributions. Additionally, four UHPC design codes were evaluated for their accuracy in estimating the shear strength of the specimens, and a simplified strut-and-tie model was developed to predict the shear strength of externally pre-stressed PUSBs. Finally, several design recommendations were proposed. This study is expected to facilitate the research and application of PUSBs. [ABSTRACT FROM AUTHOR]

• The mechanism of precast segmental UHPC beams (PUSBs) with epoxy joints subject to combined bending and shear was investigated. • The PUSBs with epoxy joints exhibit comparable structural performance with the monolithic beam. • The effect of the shear span-to-depth ratio, stirrups, and joints on the mechanical behavior of PUSBs were discussed. • Analytical models for predicting the cracking strength and ultimate capacity of PUSBs were proposed. Precast ultra-high-performance concrete (UHPC) segmental bridges (PUSBs) have become a competitive bridge type in modern civil engineering. To establish a thorough mechanistic understanding of PUSBs, seven specimens were fabricated and experimentally investigated. These specimens were designed to have different longitudinal reinforcements, construction methods, joint types, shear span-to-depth ratios (λ), stirrup ratios, and numbers of shear keys. Two failure modes were observed in the tests: flexural failure with crushing of the UHPC at the joints, and shear failure with shear tension sliding and concrete spalling of the web. Additionally, it was found that although the ultimate capacity, stiffness, and cracking load of the segmental beams were slightly lower than those of the monolithic beams, the segmental beams tended to exhibit better ductility and deformation capacity. As λ increased, the ultimate capacity and stiffness of the segmental beams decreased, whereas the growth rates of the deflection and tendon stress increased. Moreover, the stirrups showed a positive effect on the cracking control ability and shear strength of the beams. The three-keyed specimen exhibited better structural behavior than the single-keyed specimen. Finally, calculation methods were proposed to predict the cracking strength and ultimate capacity of PUSBs. [ABSTRACT FROM AUTHOR]