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A novel prefabricated segmental guardrail is proposed to facilitate connections between guardrails and between guardrails and bridge decks by casting ultrahigh-performance concrete (UHPC) joints in situ. Through finite element crash simulation analysis of three types of vehicles and crash tests of real vehicles, the prefabricated segmental guardrail with a UHPC connection was systematically evaluated in terms of its energy-absorbing capacity, vehicular acceleration, post-impact trajectory of the impacting vehicle, and behaviour of the guardrail upon impact. During the evaluation process, performance comparisons of the prefabricated segmental guardrails are made with the monolithic concrete guardrails. The results indicate that the performance of the prefabricated segmental guardrail with a UHPC connection was superior to that of the conventional concrete monolithic guardrails: it exhibited a higher level of crash performance, the occupants of the impacting vehicle were better protected, and the impacting vehicle exhibited better post-collision stability. Finally, the convenience of the prefabricated segmental guardrails with UHPC connections was proven in practical engineering applications.

Ultra-high-performance concrete (UHPC) has been regarded as promising alternative to provide reliable connections between difference segments (e.g., columns and pier footing/cap) during accelerated bridge construction (ABC) procedures. This paper proposes an innovative layered-UHPC connection for the pre-fabricated segmental (PFS) piers, whose seismic performance was validated through quasi-static experiments. Based on the test results, design procedure is presented for PFS pier with this connection, to overcome the observed drawbacks and achieve high-level performance. The layered-UHPC connection ensures the emulative performance of pre-fabricated bridges as cast-in-place (CIP) ones, as well as provides greater economic efficiency than traditional UHPC connections. Based on experimental results, key issues concerning this connection, including the tensile behavior of UHPC, height of connection region, thickness of UHPC layer and steel bars in grouting bed, are presented and discussed. Then a seismic design procedure is proposed utilizing the capacity protection philosophy. The layered-UHPC connection is expected as capacity-protected component without damage, since it provides anchorage for longitudinal steel bars. While the pre-fabricated region is designed as ductile component undergoing nonlinearity during strong earthquakes. Following the detailed elaborations about the design philosophy, requirement and implementation steps, this procedure is further presented through illustration examples using PFS piers with various heights. The results show that PFS piers designed according to this procedure could meet the requirement under both frequent and rare earthquakes. Note that the PFS piers with this layered-UHPC connections could be designed similar to and emulative as CIP ones, which is believed friendly to designers in engineering practice.

In order to improve the applicability of precast bridge columns in high intensity zones, a precast segmental column, equivalent to the cast-in-place(CIP) column was proposed, in which the ultra-high-perfornce concrete (UHPC) was used to connect precast column components. Two 1/4-scale precast segmental bridge columns assembled with UHPC and one monolithic CIP circular column with the same dimensions were designed and tested by applying cyclic quasi-static loading. Test and analysis results show that the UHPC-connected precast columns have the same typical characteristics as a conventional monolithic CIP column with respect to plastic hinge forming mechanism, failure mode, hysteretic behavior and energy dissipation capacity. There were no noteworthy cracks and damages observed around the UHPC connection areas, which may validate that the CIP column components can be firmly and reliably connected using UHPC due to its remarkable bond and confinement performance. Finally, a set of key parameters included by the Bouc-Wen-Baber-Noori (BWBN) model were identified based on the data recorded in the test. By means of the established BWBN model, the cyclic loading responses were recalculated, which matched well those from the test. This model can be further used for the seismic time- history analysis of bridge structural systems that include the UHPC connected precast columns proposed in this paper.

To reduce the weight of prefabricated cap beams, a new type of hybrid pier with a steel cap beam and single concrete column with an innovative flange–rebar–ultra-high-performance concrete (UHPC) connection structure is proposed in this paper. Focusing on the static performance of hybrid piers, a specimen with a geometric similarity ratio of 1:4 was fabricated for testing. The results showed that the ultimate load-bearing capacity reached 960 kN, and the failure mode was characterized by an obvious overall vertical displacement of 70.2 mm at the cantilever end, accompanied by local buckling in the webs between transversal diaphragms and ribs. Due to the varying-thickness design, longitudinal strains were comparable between the middle section (thin plates) and the root section (thick plates) of the cantilever beam, showing a trend of an initial increase followed by a decrease from the end of the cantilever beam to the road centerline. Meanwhile, the cross-sections of the connection joint and concrete column transformed from overall compression to eccentric compression during the test. At the ultimate state, their steel structures remained elastic, with no obvious damage in the concrete or UHPC, verifying good load-bearing capacity. Furthermore, the finite element analysis showed the new connection joint and construction method of hinged-to-rigid could reduce the column top concrete compressive stress by 18–54%, tensile stress by 11–68%, and steel cap beam Mises stress by 10%. Finally, based on the experimental and numerical studies, the safety reserve coefficient of the new hybrid pier was over 2.7.

Joints are always the focus of the precast structure for accelerated bridge construction. In this paper, a girder-to-girder joint suitable for steel-ultra-high-performance concrete (UHPC) lightweight composite bridge (LWCB) is proposed. Two flexural tests were conducted to verify the effectiveness of the proposed T-shaped girder-to-girder joint. The test results indicated that: (1) The T-shaped joint has a better cracking resistance than the traditional I-shaped joint; (2) The weak interfaces of the T-shaped joint are set in the areas with relatively lower negative bending moment, and thus the cracking risk could be decreased drastically; (3) The natural curing scheme for the joint is feasible, and the reinforcement has a very large inhibitory effect on the UHPC material shrinkage; The joint interface is the weak region of the LWCB, which requires careful consideration in future designs. Based on the experimental test results, the design and calculation methods for the deflection, crack width, and ultimate flexural capacity in the negative moment region of LWCB were presented.

Assembly construction is extensively employed in bridge construction due to its ability to accelerate construction and improve quality. To speed the recovery of bridges after major earthquakes, this study proposes an assembled connection for precast piers and footings based on assembly construction. The precast piers are connected to the footings using ultra-high-performance concrete (UHPC) post-cast cupped sockets. Two specimens are tested with a 1:4 scale, namely, the cast-in-place (CIP) specimen and, the UHPC cupped socket pier specimen. Finite element models (FEM) of a continuous girder bridge with cupped socket connections are developed and verified by experimental results. The seismic fragility analysis is conducted to investigate the difference between the cupped socket connection and the CIP connection. The experimental results showed that the plastic hinge was formed on the precast piers and there was little damage to the UHPC sockets. The results of FEA indicate that UHPC cupped socket piers have slightly higher seismic fragility than the seismic fragility of cast-in-place piers. Then, some methods were proposed to reduce the seismic fragility of UHPC cupped socket piers, and their availability was confirmed by comparing them with the seismic fragility of CIP piers. Finally, an example bridge with this connection is introduced to illustrate replacing prefabricated piers after an earthquake.

Precast beam–column connections act as vital elements of precast concrete frames. To enhance the resistance to the earthquake-induced damage and environment-induced deterioration of precast beam–column connections, an innovative precast concrete beam-to-column connection locally enhanced by prefabricated ultra-high-performance concrete (UHPC) shells was proposed. For studying the seismic behaviors of these novel connections and the influence caused by the prefabricated UHPC shell length, full-scale precast specimens were experimentally investigated using low-cyclic reversed loading tests. The obtained results were analyzed and discussed, including hysteresis curves, skeleton curves, strength and deformability, performance degradation, energy dissipation capacities, and plastic hinge length. The results reveal that the novel precast concrete beam–column connections with UHPC shells behaved satisfactorily under seismic loadings. The damage in the concrete near the lower part of the beam end is reduced by the prefabricated UHPC shells. The longer prefabricated UHPC shells were more useful for decreasing the damage to the precast concrete components and improved the structural performance. The precast specimen with 600-mm long UHPC shells can achieve a ductility of 4.87 and 4.0% higher strength than the monolithic reference specimen.

Grouted sleeve connections (GSCs) are widely used in precast concrete (PC) bridge piers due to their convenience in construction and reliable structural performance. Corrosion-induced damage significantly compromises the seismic integrity of PC bridge piers with GSCs, making effective rehabilitation urgent. However, there is a scarcity of research addressing this specific retrofit need. To bridge this gap, this work systematically investigates the efficacy of ultra-high-performance concrete (UHPC) encasement in retrofitting the quasi-static seismic resilience of corroded GSC piers. Numerical analyses were conducted using OpenSEES, in which the GSCs were equivalently modeled by determining their yield strength and cross-sectional area. Three corrosion ratios of the GSCs (20%, 40%, and 60%) were considered. The effects of UHPC compressive strength (100 MPa, 120 MPa, 150 MPa) and different retrofit heights on the quasi-static seismic performance of the bridge piers were systematically investigated. The results reveal that corrosion of the GSCs markedly compromises the quasi-static seismic behavior of PC bridge piers, notably reducing both the bearing capacity and energy dissipation capacity. Retrofitting with UHPC shells effectively enhances the yield force, peak force, yield stiffness, and energy dissipation capacity of the piers. These improvements become more substantial with higher UHPC strength and greater retrofit height. Overall, the results underscore the significant detrimental effect of sleeve corrosion on quasi-static seismic performance and confirm UHPC retrofitting as a viable and effective mitigation approach.

Although orthotropic steel decks (OSDs) have been widely used in the construction of long-span bridges, there are frequently reported fatigue cracks after years of operation, and the bridge deck overlay also presents severe damage due to OSD crack-induced stiffness reduction. Ultra-high performance concrete (UHPC), recognized as the most innovative cementitious composites and the next generation of high-performance materials, shows high strength, ductility, toughness, and good performance on durability. After its first application to the OSD bridge in the early 2000s, the orthotropic steel–UHPC composite deck has been comprehensively studied worldwide. This review will summarize some important studies and findings on the behavior and fatigue performance of the orthotropic steel–UHPC composite deck. The existing studies and engineering applications indicate that such a deck system presents good bending behavior and high fatigue performance. The failure mode of shear studs in the UHPC layer is dominated by shear fractures. The cracking of the UHPC layer shall consider the superposition effect of stress from both the whole bridge structure and local decks. While some reasonable structural details in the traditional OSD may not work for the orthotropic steel–UHPC composite deck, this paper has shown that the steel–UHPC composite deck has excellent performance in bearing capacity, stiffness, and fatigue resistance. However, the fatigue performance of the steel–UHPC composite deck and its evaluation method still need validation from engineering applications. It is recommended to evaluate the stress behavior and structural parameters, as well as fatigue life by conducting the field test under in-service traffic conditions.

Flat slabs supported by columns without beams are widely used in construction owing to their economy and efficiency. However, brittle punching shear failure at slab–column connections can cause progressive collapse. UHPC has a higher tensile strength than NSC and, when appropriately reinforced with steel fibers, exhibits strain hardening after initial cracking. These properties make Ultra-High-Performance Concrete (UHPC) ideal for durable, thin, low-cost bridge decking and heavily loaded elements and an excellent choice for improving slab–column connections that have experienced punched shear failure. This study explores the impact of UHPC layers on the punching shear behavior of reinforced concrete slabs. Sixteen slab specimens were tested with variations in UHPC layer thickness, placement, and column shape. Results demonstrate that incorporating UHPC layers significantly enhances punching shear resistance, increasing ultimate load capacity by 27–91% compared to reference specimens. Notably, thicker UHPC layers (75 mm) and bottom-placed layers exhibited superior performance in terms of ductility and toughness. Square columns outperformed circular ones in resisting punching shear. Additionally, thicker layers reduced initial stiffness, while debonding issues in 25 mm layers adversely affected structural performance. This research provides valuable insights for optimizing UHPC configurations to improve the punching shear resistance of concrete slabs, offering promising solutions for high-load structures in modern construction.