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This paper presents the development of composite beams, which consist of hybrid carbon and glass fiber-reinforced polymer (FRP) I-beams and precast, ultra-high-performance, fiber-reinforced concrete (UHPFRC) slabs. Hybrid FRPs (HFRPs) provide the advantage of high resistance to corrosion, while UHPFRC has great strength and durability. The combination of these two materials is expected to benefit structures subjected to severe environmental conditions and to respond to the need for accelerated bridge construction. Three full-scale composite beams with varied UHPFRC slab width were tested under four-point flexural loading. Bolt shear connectors with and without epoxy bonding were used in the tested beams. The bolt shear connectors and epoxy were used to resist the horizontal shear flow at the interface between the HFRP I-beam and the UHPFRC slab. The composite action between the HFRP I-beam and UHPFRC slab was investigated. The test results showed that all of the composite beams exhibited significant improvements in stiffness and strength properties, above those of single HFRP I-beams without a UHPFRC slab. A fiber model was developed to predict the strength and stiffness of the composite beam, and the model accuracy was verified. Good agreement was found between the experimental and analytical results. The high tensile strength of a carbon FRP in an HFRP tensile flange could be used effectively, and the delamination failure of an HFRP compressive flange could be prevented through the addition of a UHPFRC slab on the top flange of the HFRP I-beam. The study revealed that HFRP–UHPFRC beams were efficient and could provide a competitive, cost-effective, and sustainable solution to bridge structures.

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As all bridges get deteriorated over time, structural health monitoring of these structures has become very important for the damage identification and maintenance work. Evaluating a bridge's health condition requires the testing of a variety of physical quantities including bridge dynamic responses and the evaluation of the functions of varied bridge subsystems. In this study, both the acceleration of the deck and the dynamic rotational angle of the bearings in a long-span steel girder bridge were measured when the bridge system was excited by passing-by vehicles. e nonstationary dynamical phenomena including vibration mode interactions and coupling are observed in response spectrogram. To elaborate the phenomena, the linear vibration mode properties of the bridge are characterized by finite element analysis and are correlated with the specific modes in test. A theoretical model is presented showing the mechanism of the mode coupling and instability originated from the friction effects in bearing.is study offers some insights into the correlation between complex bridge vibrations and the bearing effects, which lays a foundation for the in situ health monitoring of bridge bearing by using dynamical testing.

The behavior of composite girders made of hybrid fiber-reinforced polymer (HFRP) I-girders, topped with precast ultra-high-performance, fiber-reinforced concrete (UHPFRC) slabs is presented in this paper. HFRP I-girders were manufactured under the pultrusion process in which unidirectional carbon fibers and bidirectional fiberglass fabric or continuous strand mat were used. Four large-scale composite girders were tested under four-point flexural loading. In the first composite girder, the HFRP I-girder was topped with a full-length precast UHPFRC slab. Twelve precast UHPFRC segments were used in each slab of the other three composite girders. Either epoxy or mortar connections were used to connect the precast UHPFRC segments. The test results showed that the flexural stiffness of the composite girder with the epoxy-connected segmental precast slabs was similar to that of the full-length precast composite girder. The mortar-connected girder exhibited more ductile behavior than the epoxy-connected girder. All the composite girders exhibited significant improvements in strength and stiffness compared with the HFRP I-girder without the UHPFRC slab. The HFRP–UHPFRC composite girders were shown to provide a promising and sustainable solution for accelerated bridge construction.