Mechaniacal Performance And Design Method Study On The Specimens Of Steel-FRP-Concrete Composite Bridge

In recent years, a new bridge structure, e.g., steel-FRP-concrete composite bridge, was emerged. This composite bridge is consisted of steel girder, FRP plate, concrete layer and shear connectors. When it was applied in practice engineering, the steel-FRP-concrete composite bridge can be separated into two different types of load capacity components, which are the steel-FRP-concrete hybrid girder set along the longitudinal direction and the FRP-concrete composite slab placed on the steel girder in the transverse direction. For a steel-FRP-concrete hybrid girder, the FRP-concrete composite slab can be used to carry the compressive force and the underneath steel girder can be applied to bear the tensile force correspondingly. Meanwhile, the compressive load and the tensile load for a FRP-concrete composite slab can be carried by the concrete and FRP plate, respectively. Therefore, the merits of the three component materials can be fully utilized when steel girders, FRP plate and concrete were arranged properly. Besides, the dead load of the composite bridge can be reduced significantly with the application of light-weighted hollow FRP plate. Based on the research project (i.e. the theoretical and experimental study on the steel-FRP-high strength concrete hollow sandwich deck with the bond-slip theory) supported by the National Natural Science Foundation of China(NSFC), the following research work was conducted by author:1) Taking into the consideration of mechanical behavior and fabrication for shear connector, different types of shear connector were designed for different interfaces. The mechanical behavior and failure mode for each type of shear connector were experimentally studied using the push-out test. Based on the test results, calculated methods for predicting the load carrying capacities of the shear connectors were proposed.2) Bending tests were conducted on two-span continuous GFRP-concrete composite slabs to investigate the flexural behavior. The influence of different boundary conditions on the mechanical behavior and the failure mode of the GFRP-concrete composite slab were studied. By considering the internal force redistribution, a method for analyzing the mechanical behavior of two-span continuous GFRP-concrete composite slab was proposed.3) GFRP-concrete composite slabs were tested under local loads to investigate their punching shear performance. The influence of different boundary conditions on the mechanical behavior and the failure mode of GFRP-concrete composite slab were also analyzed. Based on the experimental results, a method was presented to predict the punching shear capacity of GFRP-concrete composite slabs.4) Steel-GFRP-concrete composite beams formed with different connection methods were tested under static load to study their flexural behavior. The bending performances and failure modes of the composite beams were compared with each other when different connection methods were concerned and the feasibilities for epoxy resin layer and shear studs as the sheer connector between steel girder and GFRP-concrete slab were also verified. Based on the experimental results, an analytical model was proposed for calculating the ultimate flexural capacity of steel-GFRP-concrete composite beams formed with shear studs.5) Taking according to the slip effect on steel-to-FRP and FRP-to-concrete interfaces, an analytical model which can be used to calculate the sectional bending rigidities of steel-FRP-concrete composite beams was proposed. Using the proposed model, the effect of interfacial shear stiffness on the distribution of interfacial slip and interfacial shear force for steel-GFRP-concrete composite beams were analyzed. The effectiveness of the proposed model was verified with the comparison between the tested results and the predicted ones. Besides, calculation methods that can be used to calculate the additional deflection at the mid-span section and the sectional stiffness reduction factor were also established when the slip effect on steel-FRP and FRP-concrete interfaces were considered.6) The non-linear behaviors of FRP-concrete composite slabs and steel-FRP-concrete composite beams were both simulated by establishing the finite element models with the ANSYS finite element software. The effectiveness of the finite element method in analyzing the composite specimens was verified by comparing the computed results with the tested ones. Besides, the influences of sectional stiffness on the mechanical performance of two-span continuous FRP-concrete composite slabs were analyzed. By adjusting the reinforcement ratio and the thickness of the concrete layer at the beam section, different sectional stiffness for composite slabs was obtained. Meanwhile, the influences of the sectional stiffness on the mechanical performance of simply supported steel-FRP-concrete composite beams were also analyzed.7) Based on the current structural design codes, the design method for the steel-FRP-concrete composite bridge was proposed. It is belived that this design menthod can be used and refered by the relative designers.