Using experimental and numerical analysis, this paper aims at investigating the mechanical behavior in Perfobond rib (PBL) shear connectors with ultrahigh-performance concrete (UHPC)-steel composite structures. Twelve push-out specimens fabricated according to the design used for the connectors in the UHPC-steel composite structures in bridges have been investigated. The main objective of this paper was to discuss the mechanism of failure and the influence of different parameters on PBL shear connectors mechanical properties, including the diameter of transverse rebar, hole spacing and number of holes. The results showed that the failure mode of this type is different from that of conventional concrete specimens. During the failure of specimens, there are few cracks and the overall stiffness still maintain a high level, and reveal that a balance between the size of transverse rebar and the diameter of the hole. In addition, the basic form of the ultimate bearing capacity of existing PBL shearing bonds is summarized, and a new concept of steel fiber shearing in UHPC is proposed. Finally, based on the elastic foundation beam model, the full curve calculation formula of UHPC single-hole PBL shear bond is derived by using Timoshenko beam element. The formula calculation results are in good agreement with the experimental values.

Precast segmental bridge piers attract engineers due to the strengths of accelerated construction, reduced traffic disturbance and enhanced quality control. However, their widely applications in high-seismicity areas are hindered, for the insufficient capacities of energy dissipation. In this study, precast segmental piers’ seismic behaviors were investigated, focusing on the connection of ‘grouted sleeves/bonded tendons’. To this end, four piers were cyclically loaded, of one cast-in-place pier, one precast segmental pier, and two prestressed precast segmental piers. Among them, Benefits of bonded tendons were evidenced, in terms of lateral strength, ductility, energy dissipation capacity and residual drift. Of particular, bonded tendons prevented the shear-induced slip between the shaft and footing segments. Enlightened from observations, cyclic dowel-friction effect is proposed and implemented within a zero-thickness sliding spring in the finite element model, capable of capturing the shear-induced joint slip. Furthermore, seismic vulnerability assessments of the bridge piers are obtained in terms of fragility curves, by performing incremental dynamic analyses. In addition, the effects of bonded or unbounded tendons are also discussed. Two criteria are adopted to define the limit states, namely displacement ductility and residual drift. It is suggested that bonded tendons could significantly ameliorate the fragility curves of precast segmental piers.

Hammerhead pier is the preferred option in many bridge sites for its limited ground occupation. Since the bearing reactions act on the short cantilever ends of the cap beam, it is usually treated as stress-disturbed region (D region) in structural concrete. Although finite element model (FEM) can predict the response of such structures, the calculation efficiency will be sharply decreased once it enters nonlinearity. Therefore, strut-and-tie model (STM) has been promoted as an alternative approach for analyzing D regions. In this study, a loading pattern was defined to relate the axial force and bending moment of the pier column with the eccentric load ratio. Sectional analysis method and associated codes were developed to generate the STM. In addition, a full-scale hammerhead pier specimen subject to varying eccentric loads was tested. Besides, nonlinear FEM was also established to numerically investigate the response of the pier. The results indicate that the proposed STM has general applicability for modeling the hammerhead pier and shows better prediction than the FEM. The failure pattern of the hammerhead pier with a prefabricated cap beam was defined. Combining the mechanical analysis of STM and experimental results, the recommended design details for hammerhead piers were proposed.