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• 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]

• The UHPC-based precast large-cantilevered thin-walled bent caps were proposed and designed. • The structural performance of two large-scale (12.1 m long) UHPC-based bent caps was experimentally investigated. • The calculation methods for predicting the cracking strength and ultimate capacity of UHPC-based bent caps were proposed. • The design considerations for the UHPC-based bent caps were proposed. This study aimed to develop a new type of precast bent cap by using ultrahigh-performance concrete (UHPC) with prestressed tendons. The UHPC-based bent cap was designed to be lightweight and to exhibit excellent crack control as well as flexural and shear resistance. To this end, two large-scale specimens were designed and tested to identify their crack patterns, failure modes, shear behavior, and flexural behavior. The experimental results indicate that the UHPC bent caps provide excellent cracking resistance and considerable load-carrying potential after cracking, and the flexural strength dominates the design. In addition, calculation methods for the cracking strength and ultimate capacity were investigated and discussed, which can predict the strength of the UHPC bent cap with acceptable accuracy. Moreover, alternative options were proposed from different perspectives considering the construction procedure, weight reduction, and structural performance. Finally, several design considerations, i.e., the optimization of the cross-section and reinforcements, were proposed for prestressed UHPC-based bent caps. [ABSTRACT FROM AUTHOR]